diff --git a/tests/codegen/abi-repr-ext.rs b/tests/codegen/abi-repr-ext.rs
index a42f73566961e..b06d225ed70e6 100644
--- a/tests/codegen/abi-repr-ext.rs
+++ b/tests/codegen/abi-repr-ext.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 //@ revisions:x86_64 i686 aarch64-apple aarch64-windows aarch64-linux arm riscv
 
diff --git a/tests/codegen/align-offset.rs b/tests/codegen/align-offset.rs
index aeac230f718fb..21062cc0a914b 100644
--- a/tests/codegen/align-offset.rs
+++ b/tests/codegen/align-offset.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/alloc-optimisation.rs b/tests/codegen/alloc-optimisation.rs
index 6f320e68fdb30..8abeecf8550be 100644
--- a/tests/codegen/alloc-optimisation.rs
+++ b/tests/codegen/alloc-optimisation.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 #[no_mangle]
diff --git a/tests/codegen/array-clone.rs b/tests/codegen/array-clone.rs
index 2873f3cadca82..35445174684f9 100644
--- a/tests/codegen/array-clone.rs
+++ b/tests/codegen/array-clone.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/array-codegen.rs b/tests/codegen/array-codegen.rs
index fc272f2556cbf..9b0c6e8c3472e 100644
--- a/tests/codegen/array-codegen.rs
+++ b/tests/codegen/array-codegen.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C no-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/array-equality.rs b/tests/codegen/array-equality.rs
index bc5425c7a4f4e..fa0475bf4809c 100644
--- a/tests/codegen/array-equality.rs
+++ b/tests/codegen/array-equality.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Z merge-functions=disabled
+//@ compile-flags: -Copt-level=3 -Z merge-functions=disabled
 //@ only-x86_64
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/array-optimized.rs b/tests/codegen/array-optimized.rs
index 42fdbd39b7efa..000163d5519b3 100644
--- a/tests/codegen/array-optimized.rs
+++ b/tests/codegen/array-optimized.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/array-repeat.rs b/tests/codegen/array-repeat.rs
index b6f3b2e83d3e1..4c755df939034 100644
--- a/tests/codegen/array-repeat.rs
+++ b/tests/codegen/array-repeat.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 #![feature(array_repeat)]
diff --git a/tests/codegen/asm/goto.rs b/tests/codegen/asm/goto.rs
index c40a43fbe1bd3..7a87bb7983bae 100644
--- a/tests/codegen/asm/goto.rs
+++ b/tests/codegen/asm/goto.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ only-x86_64
 
 #![crate_type = "rlib"]
diff --git a/tests/codegen/asm/may_unwind.rs b/tests/codegen/asm/may_unwind.rs
index be66b3975ff87..63cdec7584c9b 100644
--- a/tests/codegen/asm/may_unwind.rs
+++ b/tests/codegen/asm/may_unwind.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ only-x86_64
 
 #![crate_type = "rlib"]
diff --git a/tests/codegen/asm/maybe-uninit.rs b/tests/codegen/asm/maybe-uninit.rs
index 55813c35a468b..d76d5cb1312e2 100644
--- a/tests/codegen/asm/maybe-uninit.rs
+++ b/tests/codegen/asm/maybe-uninit.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ only-x86_64
 
 #![crate_type = "rlib"]
diff --git a/tests/codegen/asm/multiple-options.rs b/tests/codegen/asm/multiple-options.rs
index 1ee295e32c9e9..4d87471a1939d 100644
--- a/tests/codegen/asm/multiple-options.rs
+++ b/tests/codegen/asm/multiple-options.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ only-x86_64
 
 #![crate_type = "rlib"]
diff --git a/tests/codegen/asm/options.rs b/tests/codegen/asm/options.rs
index 96a72c2f5ae90..c087f91fd4343 100644
--- a/tests/codegen/asm/options.rs
+++ b/tests/codegen/asm/options.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ only-x86_64
 
 #![crate_type = "rlib"]
diff --git a/tests/codegen/asm/x86-clobber_abi.rs b/tests/codegen/asm/x86-clobber_abi.rs
index cc563474bf8c2..5b34b4e8ef312 100644
--- a/tests/codegen/asm/x86-clobber_abi.rs
+++ b/tests/codegen/asm/x86-clobber_abi.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ only-x86_64
 
 #![crate_type = "rlib"]
diff --git a/tests/codegen/asm/x86-clobbers.rs b/tests/codegen/asm/x86-clobbers.rs
index 4094db7413468..50163b646b257 100644
--- a/tests/codegen/asm/x86-clobbers.rs
+++ b/tests/codegen/asm/x86-clobbers.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ only-x86_64
 
 #![crate_type = "rlib"]
diff --git a/tests/codegen/atomic-operations.rs b/tests/codegen/atomic-operations.rs
index 8a70c94e48053..8771b8b241998 100644
--- a/tests/codegen/atomic-operations.rs
+++ b/tests/codegen/atomic-operations.rs
@@ -1,5 +1,5 @@
 // Code generation of atomic operations.
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 use std::sync::atomic::AtomicI32;
diff --git a/tests/codegen/atomicptr.rs b/tests/codegen/atomicptr.rs
index e8c5e6a674970..4819af40ca2d2 100644
--- a/tests/codegen/atomicptr.rs
+++ b/tests/codegen/atomicptr.rs
@@ -4,7 +4,7 @@
 // ensures that we do not have such a round-trip for AtomicPtr::swap, because LLVM supports pointer
 // arguments to `atomicrmw xchg`.
 
-//@ compile-flags: -O -Cno-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -Cno-prepopulate-passes
 #![crate_type = "lib"]
 #![feature(strict_provenance_atomic_ptr)]
 
diff --git a/tests/codegen/avr/avr-func-addrspace.rs b/tests/codegen/avr/avr-func-addrspace.rs
index 7a36490fe93b8..ed8acccb1ad85 100644
--- a/tests/codegen/avr/avr-func-addrspace.rs
+++ b/tests/codegen/avr/avr-func-addrspace.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O --target=avr-unknown-gnu-atmega328 --crate-type=rlib -C panic=abort
+//@ compile-flags: -Copt-level=3 --target=avr-unknown-gnu-atmega328 --crate-type=rlib -C panic=abort
 //@ needs-llvm-components: avr
 
 // This test validates that function pointers can be stored in global variables
diff --git a/tests/codegen/binary-heap-peek-mut-pop-no-panic.rs b/tests/codegen/binary-heap-peek-mut-pop-no-panic.rs
index e3bc9a4761cfd..2c40327f62454 100644
--- a/tests/codegen/binary-heap-peek-mut-pop-no-panic.rs
+++ b/tests/codegen/binary-heap-peek-mut-pop-no-panic.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ ignore-std-debug-assertions
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/binary-search-index-no-bound-check.rs b/tests/codegen/binary-search-index-no-bound-check.rs
index a213c015a40b3..d59c0beec6419 100644
--- a/tests/codegen/binary-search-index-no-bound-check.rs
+++ b/tests/codegen/binary-search-index-no-bound-check.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 // Make sure no bounds checks are emitted when slicing or indexing
diff --git a/tests/codegen/box-uninit-bytes.rs b/tests/codegen/box-uninit-bytes.rs
index 63a6c7b841560..3b83ef3e250c4 100644
--- a/tests/codegen/box-uninit-bytes.rs
+++ b/tests/codegen/box-uninit-bytes.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 use std::mem::MaybeUninit;
diff --git a/tests/codegen/call-metadata.rs b/tests/codegen/call-metadata.rs
index b986b4467face..7ad3ded2f09de 100644
--- a/tests/codegen/call-metadata.rs
+++ b/tests/codegen/call-metadata.rs
@@ -1,7 +1,7 @@
 // Checks that range metadata gets emitted on calls to functions returning a
 // scalar value.
 
-//@ compile-flags: -O -C no-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes
 //@ max-llvm-major-version: 18
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/cast-optimized.rs b/tests/codegen/cast-optimized.rs
index 59cf40935cd54..11220c4a922b1 100644
--- a/tests/codegen/cast-optimized.rs
+++ b/tests/codegen/cast-optimized.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Z merge-functions=disabled
+//@ compile-flags: -Copt-level=3 -Z merge-functions=disabled
 #![crate_type = "lib"]
 
 // This tests that LLVM can optimize based on the niches in the source or
diff --git a/tests/codegen/cast-target-abi.rs b/tests/codegen/cast-target-abi.rs
index b3a35cbf3b1c6..a0801eb982692 100644
--- a/tests/codegen/cast-target-abi.rs
+++ b/tests/codegen/cast-target-abi.rs
@@ -1,7 +1,7 @@
 // ignore-tidy-linelength
 //@ revisions:aarch64 loongarch64 powerpc64 sparc64 x86_64
 //@ min-llvm-version: 19
-//@ compile-flags: -O -Cno-prepopulate-passes -Zlint-llvm-ir -Cllvm-args=-lint-abort-on-error
+//@ compile-flags: -Copt-level=3 -Cno-prepopulate-passes -Zlint-llvm-ir -Cllvm-args=-lint-abort-on-error
 
 //@[aarch64] compile-flags: --target aarch64-unknown-linux-gnu
 //@[aarch64] needs-llvm-components: arm
diff --git a/tests/codegen/catch-unwind.rs b/tests/codegen/catch-unwind.rs
index 48ad486fa03a6..d1ff55bcc285b 100644
--- a/tests/codegen/catch-unwind.rs
+++ b/tests/codegen/catch-unwind.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 // On x86 the closure is inlined in foo() producing something like
 // define i32 @foo() [...] {
diff --git a/tests/codegen/char-ascii-branchless.rs b/tests/codegen/char-ascii-branchless.rs
index 76d2f617ed1cd..f99066aa9aaec 100644
--- a/tests/codegen/char-ascii-branchless.rs
+++ b/tests/codegen/char-ascii-branchless.rs
@@ -1,6 +1,6 @@
 // Checks that these functions are branchless.
 //
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/checked_ilog.rs b/tests/codegen/checked_ilog.rs
index d7dfc7c29e7da..e340a45b6a96d 100644
--- a/tests/codegen/checked_ilog.rs
+++ b/tests/codegen/checked_ilog.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/checked_math.rs b/tests/codegen/checked_math.rs
index c612ddccdaa46..66667c6948818 100644
--- a/tests/codegen/checked_math.rs
+++ b/tests/codegen/checked_math.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Z merge-functions=disabled
+//@ compile-flags: -Copt-level=3 -Z merge-functions=disabled
 
 #![crate_type = "lib"]
 #![feature(unchecked_shifts)]
diff --git a/tests/codegen/clone_as_copy.rs b/tests/codegen/clone_as_copy.rs
index 6ba198297e226..c39f120044c09 100644
--- a/tests/codegen/clone_as_copy.rs
+++ b/tests/codegen/clone_as_copy.rs
@@ -1,7 +1,7 @@
 //@ revisions: DEBUGINFO NODEBUGINFO
 //@ compile-flags: -Zunsound-mir-opts
 // FIXME: see <https://github.com/rust-lang/rust/issues/132353>
-//@ compile-flags: -O -Cno-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -Cno-prepopulate-passes
 //@ [DEBUGINFO] compile-flags: -Cdebuginfo=full
 
 // From https://github.com/rust-lang/rust/issues/128081.
diff --git a/tests/codegen/common_prim_int_ptr.rs b/tests/codegen/common_prim_int_ptr.rs
index aa7ebb4c9119d..8eb0502417417 100644
--- a/tests/codegen/common_prim_int_ptr.rs
+++ b/tests/codegen/common_prim_int_ptr.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 #![feature(core_intrinsics)]
diff --git a/tests/codegen/const-array.rs b/tests/codegen/const-array.rs
index f2b331c315dce..e257d8acc0881 100644
--- a/tests/codegen/const-array.rs
+++ b/tests/codegen/const-array.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/cross-crate-inlining/always-inline.rs b/tests/codegen/cross-crate-inlining/always-inline.rs
index d3a35dadb67bc..df28b3fe197cd 100644
--- a/tests/codegen/cross-crate-inlining/always-inline.rs
+++ b/tests/codegen/cross-crate-inlining/always-inline.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ aux-build:always.rs
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/cross-crate-inlining/auxiliary/always.rs b/tests/codegen/cross-crate-inlining/auxiliary/always.rs
index 7f524e17d34a1..6ee3f81e3c879 100644
--- a/tests/codegen/cross-crate-inlining/auxiliary/always.rs
+++ b/tests/codegen/cross-crate-inlining/auxiliary/always.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Zcross-crate-inline-threshold=always
+//@ compile-flags: -Copt-level=3 -Zcross-crate-inline-threshold=always
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/cross-crate-inlining/auxiliary/leaf.rs b/tests/codegen/cross-crate-inlining/auxiliary/leaf.rs
index 5895812b5ee51..d059a3d0a73b8 100644
--- a/tests/codegen/cross-crate-inlining/auxiliary/leaf.rs
+++ b/tests/codegen/cross-crate-inlining/auxiliary/leaf.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/cross-crate-inlining/auxiliary/never.rs b/tests/codegen/cross-crate-inlining/auxiliary/never.rs
index 3a391608df849..55c90809ec18f 100644
--- a/tests/codegen/cross-crate-inlining/auxiliary/never.rs
+++ b/tests/codegen/cross-crate-inlining/auxiliary/never.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Zcross-crate-inline-threshold=never
+//@ compile-flags: -Copt-level=3 -Zcross-crate-inline-threshold=never
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/cross-crate-inlining/leaf-inlining.rs b/tests/codegen/cross-crate-inlining/leaf-inlining.rs
index b47898f750a24..37132312ca94c 100644
--- a/tests/codegen/cross-crate-inlining/leaf-inlining.rs
+++ b/tests/codegen/cross-crate-inlining/leaf-inlining.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Zcross-crate-inline-threshold=yes
+//@ compile-flags: -Copt-level=3 -Zcross-crate-inline-threshold=yes
 //@ aux-build:leaf.rs
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/cross-crate-inlining/never-inline.rs b/tests/codegen/cross-crate-inlining/never-inline.rs
index eedf90ceec0fc..759f65d9d42b2 100644
--- a/tests/codegen/cross-crate-inlining/never-inline.rs
+++ b/tests/codegen/cross-crate-inlining/never-inline.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ aux-build:never.rs
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/dealloc-no-unwind.rs b/tests/codegen/dealloc-no-unwind.rs
index ead26da610e25..c560d7a993209 100644
--- a/tests/codegen/dealloc-no-unwind.rs
+++ b/tests/codegen/dealloc-no-unwind.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/debug-fndef-size.rs b/tests/codegen/debug-fndef-size.rs
index c58a8228967a4..8f716c34e7b74 100644
--- a/tests/codegen/debug-fndef-size.rs
+++ b/tests/codegen/debug-fndef-size.rs
@@ -1,7 +1,7 @@
 // Verify that `i32::cmp` FnDef type is declared with a size of 0 and an
 // alignment of 8 bits (1 byte) in LLVM debuginfo.
 
-//@ compile-flags: -O -g -Cno-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -g -Cno-prepopulate-passes
 //@ ignore-msvc the types are mangled differently
 
 use std::cmp::Ordering;
diff --git a/tests/codegen/debuginfo-constant-locals.rs b/tests/codegen/debuginfo-constant-locals.rs
index c8f1d964722ef..580c69c05a54d 100644
--- a/tests/codegen/debuginfo-constant-locals.rs
+++ b/tests/codegen/debuginfo-constant-locals.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -g -O
+//@ compile-flags: -g -Copt-level=3
 
 // Check that simple constant values are preserved in debuginfo across both MIR opts and LLVM opts
 
diff --git a/tests/codegen/debuginfo-inline-callsite-location.rs b/tests/codegen/debuginfo-inline-callsite-location.rs
index c31788d82db32..59ade52ad3276 100644
--- a/tests/codegen/debuginfo-inline-callsite-location.rs
+++ b/tests/codegen/debuginfo-inline-callsite-location.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -g -O -C panic=abort
+//@ compile-flags: -g -Copt-level=3 -C panic=abort
 
 // Check that each inline call site for the same function uses the same "sub-program" so that LLVM
 // can correctly merge the debug info if it merges the inlined code (e.g., for merging of tail
diff --git a/tests/codegen/deduced-param-attrs.rs b/tests/codegen/deduced-param-attrs.rs
index 5e7c571b63f8d..22db090d4d889 100644
--- a/tests/codegen/deduced-param-attrs.rs
+++ b/tests/codegen/deduced-param-attrs.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 #![allow(incomplete_features)]
diff --git a/tests/codegen/dont-shufflevector-bswaps.rs b/tests/codegen/dont-shufflevector-bswaps.rs
new file mode 100644
index 0000000000000..c30fe89ba7511
--- /dev/null
+++ b/tests/codegen/dont-shufflevector-bswaps.rs
@@ -0,0 +1,36 @@
+//@ revisions: OPT2 OPT3
+//@ [OPT2] compile-flags: -Copt-level=2
+//@ [OPT3] compile-flags: -C opt-level=3
+//@ min-llvm-version: 18.1.3
+
+#![crate_type = "lib"]
+#![no_std]
+
+// The code is from https://github.com/rust-lang/rust/issues/122805.
+// Ensure we do not generate the shufflevector instruction
+// to avoid complicating the code.
+// CHECK-LABEL: define{{.*}}void @convert(
+// CHECK-NOT: shufflevector
+// On higher opt levels, this should just be a bswap:
+// OPT3: load <8 x i16>
+// OPT3-NEXT: call <8 x i16> @llvm.bswap
+// OPT3-NEXT: store <8 x i16>
+// OPT3-NEXT: ret void
+#[no_mangle]
+pub fn convert(value: [u16; 8]) -> [u8; 16] {
+    #[cfg(target_endian = "little")]
+    let bswap = u16::to_be;
+    #[cfg(target_endian = "big")]
+    let bswap = u16::to_le;
+    let addr16 = [
+        bswap(value[0]),
+        bswap(value[1]),
+        bswap(value[2]),
+        bswap(value[3]),
+        bswap(value[4]),
+        bswap(value[5]),
+        bswap(value[6]),
+        bswap(value[7]),
+    ];
+    unsafe { core::mem::transmute::<_, [u8; 16]>(addr16) }
+}
diff --git a/tests/codegen/drop-in-place-noalias.rs b/tests/codegen/drop-in-place-noalias.rs
index 2dc769df1c92b..bff2f52781f23 100644
--- a/tests/codegen/drop-in-place-noalias.rs
+++ b/tests/codegen/drop-in-place-noalias.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C no-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes
 
 // Tests that the compiler can apply `noalias` and other &mut attributes to `drop_in_place`.
 // Note that non-Unpin types should not get `noalias`, matching &mut behavior.
diff --git a/tests/codegen/dst-vtable-align-nonzero.rs b/tests/codegen/dst-vtable-align-nonzero.rs
index cb07e43238c10..1404bd64f500c 100644
--- a/tests/codegen/dst-vtable-align-nonzero.rs
+++ b/tests/codegen/dst-vtable-align-nonzero.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Z merge-functions=disabled
+//@ compile-flags: -Copt-level=3 -Z merge-functions=disabled
 
 #![crate_type = "lib"]
 #![feature(core_intrinsics)]
diff --git a/tests/codegen/dst-vtable-size-range.rs b/tests/codegen/dst-vtable-size-range.rs
index 69d8e68497ca6..670f5e8d553fa 100644
--- a/tests/codegen/dst-vtable-size-range.rs
+++ b/tests/codegen/dst-vtable-size-range.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Z merge-functions=disabled
+//@ compile-flags: -Copt-level=3 -Z merge-functions=disabled
 
 #![crate_type = "lib"]
 #![feature(core_intrinsics)]
diff --git a/tests/codegen/emscripten-catch-unwind-js-eh.rs b/tests/codegen/emscripten-catch-unwind-js-eh.rs
index b15fb40b68f00..018ad5454fc23 100644
--- a/tests/codegen/emscripten-catch-unwind-js-eh.rs
+++ b/tests/codegen/emscripten-catch-unwind-js-eh.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O --target wasm32-unknown-emscripten
+//@ compile-flags: -Copt-level=3 --target wasm32-unknown-emscripten
 //@ needs-llvm-components: webassembly
 
 // Emscripten has its own unique implementation of catch_unwind (in `codegen_emcc_try`),
diff --git a/tests/codegen/emscripten-catch-unwind-wasm-eh.rs b/tests/codegen/emscripten-catch-unwind-wasm-eh.rs
index 72395f432d5f8..0fc9ae96720e4 100644
--- a/tests/codegen/emscripten-catch-unwind-wasm-eh.rs
+++ b/tests/codegen/emscripten-catch-unwind-wasm-eh.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O --target wasm32-unknown-emscripten -Z emscripten-wasm-eh
+//@ compile-flags: -Copt-level=3 --target wasm32-unknown-emscripten -Z emscripten-wasm-eh
 //@ needs-llvm-components: webassembly
 
 // Emscripten catch_unwind using wasm exceptions
diff --git a/tests/codegen/enum/enum-bounds-check-derived-idx.rs b/tests/codegen/enum/enum-bounds-check-derived-idx.rs
index 15280cb2e6c87..a5785f4addf05 100644
--- a/tests/codegen/enum/enum-bounds-check-derived-idx.rs
+++ b/tests/codegen/enum/enum-bounds-check-derived-idx.rs
@@ -1,6 +1,6 @@
 // This test checks an optimization that is not guaranteed to work. This test case should not block
 // a future LLVM update.
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/enum/enum-bounds-check-issue-13926.rs b/tests/codegen/enum/enum-bounds-check-issue-13926.rs
index b60ff38ce392c..6e8e5035b0d00 100644
--- a/tests/codegen/enum/enum-bounds-check-issue-13926.rs
+++ b/tests/codegen/enum/enum-bounds-check-issue-13926.rs
@@ -1,6 +1,6 @@
 // This test checks an optimization that is not guaranteed to work. This test case should not block
 // a future LLVM update.
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/enum/enum-bounds-check.rs b/tests/codegen/enum/enum-bounds-check.rs
index c44c007ed6a9f..5362598ca7c43 100644
--- a/tests/codegen/enum/enum-bounds-check.rs
+++ b/tests/codegen/enum/enum-bounds-check.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/enum/enum-early-otherwise-branch.rs b/tests/codegen/enum/enum-early-otherwise-branch.rs
index 07c8aed2624c1..8d39d8e9b7466 100644
--- a/tests/codegen/enum/enum-early-otherwise-branch.rs
+++ b/tests/codegen/enum/enum-early-otherwise-branch.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/enum/unreachable_enum_default_branch.rs b/tests/codegen/enum/unreachable_enum_default_branch.rs
index 76a92496c0729..55b165fc111dd 100644
--- a/tests/codegen/enum/unreachable_enum_default_branch.rs
+++ b/tests/codegen/enum/unreachable_enum_default_branch.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/error-provide.rs b/tests/codegen/error-provide.rs
index 68dd383e5cce0..25a66078fd4a8 100644
--- a/tests/codegen/error-provide.rs
+++ b/tests/codegen/error-provide.rs
@@ -1,6 +1,6 @@
 // Codegen test for #126242
 
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 #![feature(error_generic_member_access)]
 use std::error::Request;
diff --git a/tests/codegen/external-no-mangle-statics.rs b/tests/codegen/external-no-mangle-statics.rs
index a44867ff9230f..dc4eca8c7b486 100644
--- a/tests/codegen/external-no-mangle-statics.rs
+++ b/tests/codegen/external-no-mangle-statics.rs
@@ -1,6 +1,6 @@
 //@ revisions: lib staticlib
 //@ ignore-emscripten default visibility is hidden
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ [lib] compile-flags: --crate-type lib
 //@ [staticlib] compile-flags: --crate-type staticlib
 // `#[no_mangle]`d static variables always have external linkage, i.e., no `internal` in their
diff --git a/tests/codegen/f128-wasm32-callconv.rs b/tests/codegen/f128-wasm32-callconv.rs
index 8b1b5e7fb013f..7dccbda18f1aa 100644
--- a/tests/codegen/f128-wasm32-callconv.rs
+++ b/tests/codegen/f128-wasm32-callconv.rs
@@ -1,7 +1,7 @@
 //! Verify that Rust implements the expected calling convention for `f128`
 
 //@ add-core-stubs
-//@ compile-flags: -O --target wasm32-wasip1
+//@ compile-flags: -Copt-level=3 --target wasm32-wasip1
 //@ needs-llvm-components: webassembly
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/fastcall-inreg.rs b/tests/codegen/fastcall-inreg.rs
index 2459ec1539e43..00b390bf1bf17 100644
--- a/tests/codegen/fastcall-inreg.rs
+++ b/tests/codegen/fastcall-inreg.rs
@@ -2,7 +2,7 @@
 // as "inreg" like the C/C++ compilers for the platforms.
 // x86 only.
 
-//@ compile-flags: --target i686-unknown-linux-gnu -O -C no-prepopulate-passes
+//@ compile-flags: --target i686-unknown-linux-gnu -Cno-prepopulate-passes -Copt-level=3
 //@ needs-llvm-components: x86
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/fewer-names.rs b/tests/codegen/fewer-names.rs
index a171629a076b2..ff7a916b619c1 100644
--- a/tests/codegen/fewer-names.rs
+++ b/tests/codegen/fewer-names.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -Coverflow-checks=no -O
+//@ compile-flags: -Coverflow-checks=no -Copt-level=3
 //@ revisions: YES NO
 //@ [YES]compile-flags: -Zfewer-names=yes
 //@ [NO] compile-flags: -Zfewer-names=no
diff --git a/tests/codegen/function-arguments.rs b/tests/codegen/function-arguments.rs
index 1a211dfe096b3..f0708a7a109f2 100644
--- a/tests/codegen/function-arguments.rs
+++ b/tests/codegen/function-arguments.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C no-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes
 #![crate_type = "lib"]
 #![feature(rustc_attrs)]
 #![feature(dyn_star)]
diff --git a/tests/codegen/hint/cold_path.rs b/tests/codegen/hint/cold_path.rs
index dac72073f858b..149abe474f67b 100644
--- a/tests/codegen/hint/cold_path.rs
+++ b/tests/codegen/hint/cold_path.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 #![feature(cold_path)]
 
diff --git a/tests/codegen/hint/likely.rs b/tests/codegen/hint/likely.rs
index 2f589cc99d282..75f9e7aae367d 100644
--- a/tests/codegen/hint/likely.rs
+++ b/tests/codegen/hint/likely.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 #![feature(likely_unlikely)]
 
diff --git a/tests/codegen/hint/unlikely.rs b/tests/codegen/hint/unlikely.rs
index 328533f30816c..248b1e2537e96 100644
--- a/tests/codegen/hint/unlikely.rs
+++ b/tests/codegen/hint/unlikely.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 #![feature(likely_unlikely)]
 
diff --git a/tests/codegen/i128-wasm32-callconv.rs b/tests/codegen/i128-wasm32-callconv.rs
index c6d25fbe8bea2..9d73d270ef3d0 100644
--- a/tests/codegen/i128-wasm32-callconv.rs
+++ b/tests/codegen/i128-wasm32-callconv.rs
@@ -1,7 +1,7 @@
 //! Verify that Rust implements the expected calling convention for `i128`/`u128`.
 
 //@ add-core-stubs
-//@ compile-flags: -O --target wasm32-wasip1
+//@ compile-flags: -Copt-level=3 --target wasm32-wasip1
 //@ needs-llvm-components: webassembly
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/i128-x86-align.rs b/tests/codegen/i128-x86-align.rs
index ac101b72513dd..75802b0c5056a 100644
--- a/tests/codegen/i128-x86-align.rs
+++ b/tests/codegen/i128-x86-align.rs
@@ -1,5 +1,5 @@
 //@ only-x86_64
-//@ compile-flags: -O -C no-prepopulate-passes --crate-type=lib
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes --crate-type=lib
 
 // On LLVM 17 and earlier LLVM's own data layout specifies that i128 has 8 byte alignment,
 // while rustc wants it to have 16 byte alignment. This test checks that we handle this
diff --git a/tests/codegen/integer-overflow.rs b/tests/codegen/integer-overflow.rs
index a6407476fc209..80362247a86f1 100644
--- a/tests/codegen/integer-overflow.rs
+++ b/tests/codegen/integer-overflow.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C overflow-checks=on
+//@ compile-flags: -Copt-level=3 -C overflow-checks=on
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/intrinsics/aggregate-thin-pointer.rs b/tests/codegen/intrinsics/aggregate-thin-pointer.rs
index aa3bf7e8b14a4..bd590ce91809f 100644
--- a/tests/codegen/intrinsics/aggregate-thin-pointer.rs
+++ b/tests/codegen/intrinsics/aggregate-thin-pointer.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C no-prepopulate-passes -Z mir-enable-passes=-InstSimplify
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes -Z mir-enable-passes=-InstSimplify
 //@ only-64bit (so I don't need to worry about usize)
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/intrinsics/cold_path.rs b/tests/codegen/intrinsics/cold_path.rs
index 24ee84e07bf1d..fd75324b671e2 100644
--- a/tests/codegen/intrinsics/cold_path.rs
+++ b/tests/codegen/intrinsics/cold_path.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 #![feature(core_intrinsics)]
 
diff --git a/tests/codegen/intrinsics/compare_bytes.rs b/tests/codegen/intrinsics/compare_bytes.rs
index cd592918fb0c2..3ab0e4e97e09d 100644
--- a/tests/codegen/intrinsics/compare_bytes.rs
+++ b/tests/codegen/intrinsics/compare_bytes.rs
@@ -1,5 +1,5 @@
 //@ revisions: INT32 INT16
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ [INT32] ignore-16bit
 //@ [INT16] only-16bit
 
diff --git a/tests/codegen/intrinsics/likely.rs b/tests/codegen/intrinsics/likely.rs
index e318390db205c..c5e3c466f4525 100644
--- a/tests/codegen/intrinsics/likely.rs
+++ b/tests/codegen/intrinsics/likely.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 #![feature(core_intrinsics)]
 
diff --git a/tests/codegen/intrinsics/likely_assert.rs b/tests/codegen/intrinsics/likely_assert.rs
index 0ddbd6206aeea..87ffb4ee3fb65 100644
--- a/tests/codegen/intrinsics/likely_assert.rs
+++ b/tests/codegen/intrinsics/likely_assert.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 #[no_mangle]
diff --git a/tests/codegen/intrinsics/nontemporal.rs b/tests/codegen/intrinsics/nontemporal.rs
index ff2d629606688..af8892d30e7f4 100644
--- a/tests/codegen/intrinsics/nontemporal.rs
+++ b/tests/codegen/intrinsics/nontemporal.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@revisions: with_nontemporal without_nontemporal
 //@[with_nontemporal] compile-flags: --target aarch64-unknown-linux-gnu
 //@[with_nontemporal] needs-llvm-components: aarch64
diff --git a/tests/codegen/intrinsics/offset.rs b/tests/codegen/intrinsics/offset.rs
index d4791cd30b0be..d76d3e705abad 100644
--- a/tests/codegen/intrinsics/offset.rs
+++ b/tests/codegen/intrinsics/offset.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C no-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes
 
 #![crate_type = "lib"]
 #![feature(core_intrinsics)]
diff --git a/tests/codegen/intrinsics/ptr_metadata.rs b/tests/codegen/intrinsics/ptr_metadata.rs
index f4bf5a1f5f173..87a32fa3d2468 100644
--- a/tests/codegen/intrinsics/ptr_metadata.rs
+++ b/tests/codegen/intrinsics/ptr_metadata.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C no-prepopulate-passes -Z inline-mir
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes -Z inline-mir
 //@ only-64bit (so I don't need to worry about usize)
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/intrinsics/select_unpredictable.rs b/tests/codegen/intrinsics/select_unpredictable.rs
index ea6127a48bf3f..68a02c8342d06 100644
--- a/tests/codegen/intrinsics/select_unpredictable.rs
+++ b/tests/codegen/intrinsics/select_unpredictable.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Zmerge-functions=disabled
+//@ compile-flags: -Copt-level=3 -Zmerge-functions=disabled
 
 #![feature(core_intrinsics)]
 #![feature(select_unpredictable)]
diff --git a/tests/codegen/intrinsics/transmute-x64.rs b/tests/codegen/intrinsics/transmute-x64.rs
index ea1c6b0e7e801..fe68f18366701 100644
--- a/tests/codegen/intrinsics/transmute-x64.rs
+++ b/tests/codegen/intrinsics/transmute-x64.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C no-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes
 //@ only-x86_64 (it's using arch-specific types)
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/intrinsics/transmute.rs b/tests/codegen/intrinsics/transmute.rs
index 8c8e975d327a2..541333a52b0df 100644
--- a/tests/codegen/intrinsics/transmute.rs
+++ b/tests/codegen/intrinsics/transmute.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C no-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes
 //@ only-64bit (so I don't need to worry about usize)
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/intrinsics/unlikely.rs b/tests/codegen/intrinsics/unlikely.rs
index 2d776031a52ef..90ebf070d2700 100644
--- a/tests/codegen/intrinsics/unlikely.rs
+++ b/tests/codegen/intrinsics/unlikely.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 #![feature(core_intrinsics)]
 
diff --git a/tests/codegen/is_val_statically_known.rs b/tests/codegen/is_val_statically_known.rs
index fe432d3bcc4de..8119d3a3bf678 100644
--- a/tests/codegen/is_val_statically_known.rs
+++ b/tests/codegen/is_val_statically_known.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: --crate-type=lib -Zmerge-functions=disabled -O
+//@ compile-flags: --crate-type=lib -Zmerge-functions=disabled -Copt-level=3
 
 #![feature(core_intrinsics)]
 #![feature(f16, f128)]
diff --git a/tests/codegen/issues/issue-101048.rs b/tests/codegen/issues/issue-101048.rs
index fa6dc550f301e..cfe65e758fdbd 100644
--- a/tests/codegen/issues/issue-101048.rs
+++ b/tests/codegen/issues/issue-101048.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-101082.rs b/tests/codegen/issues/issue-101082.rs
index 4be1b6cb168e8..048b69d207b6d 100644
--- a/tests/codegen/issues/issue-101082.rs
+++ b/tests/codegen/issues/issue-101082.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ revisions: host x86-64-v3
 
 // This particular CPU regressed in #131563
diff --git a/tests/codegen/issues/issue-101814.rs b/tests/codegen/issues/issue-101814.rs
index e3843e9edb0bd..668ec8476e8c0 100644
--- a/tests/codegen/issues/issue-101814.rs
+++ b/tests/codegen/issues/issue-101814.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-103132.rs b/tests/codegen/issues/issue-103132.rs
index 8c1a17c8b78c2..623cab92806dc 100644
--- a/tests/codegen/issues/issue-103132.rs
+++ b/tests/codegen/issues/issue-103132.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C overflow-checks
+//@ compile-flags: -Copt-level=3 -C overflow-checks
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-103285-ptr-addr-overflow-check.rs b/tests/codegen/issues/issue-103285-ptr-addr-overflow-check.rs
index 122f02fbbc55b..3ada5412e8335 100644
--- a/tests/codegen/issues/issue-103285-ptr-addr-overflow-check.rs
+++ b/tests/codegen/issues/issue-103285-ptr-addr-overflow-check.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C debug-assertions=yes
+//@ compile-flags: -Copt-level=3 -C debug-assertions=yes
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-103327.rs b/tests/codegen/issues/issue-103327.rs
index f8cf273e4a6c2..4de3cfd12a09a 100644
--- a/tests/codegen/issues/issue-103327.rs
+++ b/tests/codegen/issues/issue-103327.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-103840.rs b/tests/codegen/issues/issue-103840.rs
index 14f157771e077..c6c5098bdd04f 100644
--- a/tests/codegen/issues/issue-103840.rs
+++ b/tests/codegen/issues/issue-103840.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 pub fn foo(t: &mut Vec<usize>) {
diff --git a/tests/codegen/issues/issue-105386-ub-in-debuginfo.rs b/tests/codegen/issues/issue-105386-ub-in-debuginfo.rs
index db9eeda19a6c6..848aa910b584e 100644
--- a/tests/codegen/issues/issue-105386-ub-in-debuginfo.rs
+++ b/tests/codegen/issues/issue-105386-ub-in-debuginfo.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: --crate-type=lib -O -Cdebuginfo=2 -Cno-prepopulate-passes -Zmir-enable-passes=-ScalarReplacementOfAggregates
+//@ compile-flags: --crate-type=lib -Copt-level=3 -Cdebuginfo=2 -Cno-prepopulate-passes -Zmir-enable-passes=-ScalarReplacementOfAggregates
 // MIR SROA will decompose the closure
 #![feature(stmt_expr_attributes)]
 
diff --git a/tests/codegen/issues/issue-106369.rs b/tests/codegen/issues/issue-106369.rs
index fd375e4e60584..3583d20c9fa1c 100644
--- a/tests/codegen/issues/issue-106369.rs
+++ b/tests/codegen/issues/issue-106369.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-107681-unwrap_unchecked.rs b/tests/codegen/issues/issue-107681-unwrap_unchecked.rs
index 7d9679d2322b2..fd7296de4c864 100644
--- a/tests/codegen/issues/issue-107681-unwrap_unchecked.rs
+++ b/tests/codegen/issues/issue-107681-unwrap_unchecked.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ min-llvm-version: 19
 
 // Test for #107681.
diff --git a/tests/codegen/issues/issue-108395-branchy-bool-match.rs b/tests/codegen/issues/issue-108395-branchy-bool-match.rs
index 24f5c0f663532..96387e791b03a 100644
--- a/tests/codegen/issues/issue-108395-branchy-bool-match.rs
+++ b/tests/codegen/issues/issue-108395-branchy-bool-match.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Zmerge-functions=disabled
+//@ compile-flags: -Copt-level=3 -Zmerge-functions=disabled
 //! Test for <https://github.com/rust-lang/rust/issues/108395>. Check that
 //! matching on two bools with wildcards does not produce branches.
 #![crate_type = "lib"]
diff --git a/tests/codegen/issues/issue-109328-split_first.rs b/tests/codegen/issues/issue-109328-split_first.rs
index 7f7957593d2de..26235edfc190f 100644
--- a/tests/codegen/issues/issue-109328-split_first.rs
+++ b/tests/codegen/issues/issue-109328-split_first.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-110797-enum-jump-same.rs b/tests/codegen/issues/issue-110797-enum-jump-same.rs
index f114e0e260eb5..b5f7c08795bc6 100644
--- a/tests/codegen/issues/issue-110797-enum-jump-same.rs
+++ b/tests/codegen/issues/issue-110797-enum-jump-same.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-111603.rs b/tests/codegen/issues/issue-111603.rs
index 41bfb493ff580..2ba5a3f876aed 100644
--- a/tests/codegen/issues/issue-111603.rs
+++ b/tests/codegen/issues/issue-111603.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 #![feature(get_mut_unchecked, new_uninit)]
diff --git a/tests/codegen/issues/issue-112509-slice-get-andthen-get.rs b/tests/codegen/issues/issue-112509-slice-get-andthen-get.rs
index aee2edd8dfad2..3909b203d0897 100644
--- a/tests/codegen/issues/issue-112509-slice-get-andthen-get.rs
+++ b/tests/codegen/issues/issue-112509-slice-get-andthen-get.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 // CHECK-LABEL: @write_u8_variant_a
diff --git a/tests/codegen/issues/issue-114312.rs b/tests/codegen/issues/issue-114312.rs
index be5b999afd0b0..e9418249089dd 100644
--- a/tests/codegen/issues/issue-114312.rs
+++ b/tests/codegen/issues/issue-114312.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ only-x86_64-unknown-linux-gnu
 
 // We want to check that this function does not mis-optimize to loop jumping.
diff --git a/tests/codegen/issues/issue-115385-llvm-jump-threading.rs b/tests/codegen/issues/issue-115385-llvm-jump-threading.rs
index 55aa69a7de034..8cabd94f2028c 100644
--- a/tests/codegen/issues/issue-115385-llvm-jump-threading.rs
+++ b/tests/codegen/issues/issue-115385-llvm-jump-threading.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Ccodegen-units=1
+//@ compile-flags: -Copt-level=3 -Ccodegen-units=1
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-116878.rs b/tests/codegen/issues/issue-116878.rs
index a09fac42c0182..daf46c8bb554a 100644
--- a/tests/codegen/issues/issue-116878.rs
+++ b/tests/codegen/issues/issue-116878.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 /// Make sure no bounds checks are emitted after a `get_unchecked`.
diff --git a/tests/codegen/issues/issue-118306.rs b/tests/codegen/issues/issue-118306.rs
index 0778ab3fde970..f9f3e0c0529cf 100644
--- a/tests/codegen/issues/issue-118306.rs
+++ b/tests/codegen/issues/issue-118306.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ min-llvm-version: 19
 //@ only-x86_64
 
diff --git a/tests/codegen/issues/issue-118392.rs b/tests/codegen/issues/issue-118392.rs
index ce2332b4c3c75..07de8d9b237a7 100644
--- a/tests/codegen/issues/issue-118392.rs
+++ b/tests/codegen/issues/issue-118392.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 // CHECK-LABEL: @div2
diff --git a/tests/codegen/issues/issue-119422.rs b/tests/codegen/issues/issue-119422.rs
index 682430a79f4a9..e1a082c377f8b 100644
--- a/tests/codegen/issues/issue-119422.rs
+++ b/tests/codegen/issues/issue-119422.rs
@@ -1,7 +1,7 @@
 //! This test checks that compiler don't generate useless compares to zeros
 //! for `NonZero` integer types.
 //!
-//@ compile-flags: -O --edition=2021 -Zmerge-functions=disabled
+//@ compile-flags: -Copt-level=3 --edition=2021 -Zmerge-functions=disabled
 //@ only-64bit (because the LLVM type of i64 for usize shows up)
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-121719-common-field-offset.rs b/tests/codegen/issues/issue-121719-common-field-offset.rs
index 11a8aa8dcd144..9f5f44e037555 100644
--- a/tests/codegen/issues/issue-121719-common-field-offset.rs
+++ b/tests/codegen/issues/issue-121719-common-field-offset.rs
@@ -1,7 +1,7 @@
 //! This test checks that match branches which all access a field
 //! at the same offset are merged together.
 //!
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 #[repr(C)]
diff --git a/tests/codegen/issues/issue-122600-ptr-discriminant-update.rs b/tests/codegen/issues/issue-122600-ptr-discriminant-update.rs
index 4b520a6206951..fdb8f06df8005 100644
--- a/tests/codegen/issues/issue-122600-ptr-discriminant-update.rs
+++ b/tests/codegen/issues/issue-122600-ptr-discriminant-update.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ min-llvm-version: 19
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/issues/issue-122805.rs b/tests/codegen/issues/issue-122805.rs
deleted file mode 100644
index 16dae801ee43a..0000000000000
--- a/tests/codegen/issues/issue-122805.rs
+++ /dev/null
@@ -1,58 +0,0 @@
-//@ revisions: OPT2 OPT3WINX64 OPT3LINX64
-//@ [OPT2] compile-flags: -O
-//@ [OPT3LINX64] compile-flags: -C opt-level=3
-//@ [OPT3WINX64] compile-flags: -C opt-level=3
-//@ [OPT3LINX64] only-linux
-//@ [OPT3WINX64] only-windows
-//@ [OPT3LINX64] only-x86_64
-//@ [OPT3WINX64] only-x86_64
-//@ min-llvm-version: 18.1.3
-
-#![crate_type = "lib"]
-#![no_std]
-
-// The code is from https://github.com/rust-lang/rust/issues/122805.
-// Ensure we do not generate the shufflevector instruction
-// to avoid complicating the code.
-// CHECK-LABEL: define{{.*}}void @convert(
-// CHECK-NOT: shufflevector
-// OPT2: store i16
-// OPT2-NEXT: getelementptr inbounds{{( nuw)?}} i8, {{.+}} 2
-// OPT2-NEXT: store i16
-// OPT2-NEXT: getelementptr inbounds{{( nuw)?}} i8, {{.+}} 4
-// OPT2-NEXT: store i16
-// OPT2-NEXT: getelementptr inbounds{{( nuw)?}} i8, {{.+}} 6
-// OPT2-NEXT: store i16
-// OPT2-NEXT: getelementptr inbounds{{( nuw)?}} i8, {{.+}} 8
-// OPT2-NEXT: store i16
-// OPT2-NEXT: getelementptr inbounds{{( nuw)?}} i8, {{.+}} 10
-// OPT2-NEXT: store i16
-// OPT2-NEXT: getelementptr inbounds{{( nuw)?}} i8, {{.+}} 12
-// OPT2-NEXT: store i16
-// OPT2-NEXT: getelementptr inbounds{{( nuw)?}} i8, {{.+}} 14
-// OPT2-NEXT: store i16
-// OPT3LINX64: load <8 x i16>
-// OPT3LINX64-NEXT: call <8 x i16> @llvm.bswap
-// OPT3LINX64-NEXT: store <8 x i16>
-// OPT3WINX64: load <8 x i16>
-// OPT3WINX64-NEXT: call <8 x i16> @llvm.bswap
-// OPT3WINX64-NEXT: store <8 x i16>
-// CHECK-NEXT: ret void
-#[no_mangle]
-pub fn convert(value: [u16; 8]) -> [u8; 16] {
-    #[cfg(target_endian = "little")]
-    let bswap = u16::to_be;
-    #[cfg(target_endian = "big")]
-    let bswap = u16::to_le;
-    let addr16 = [
-        bswap(value[0]),
-        bswap(value[1]),
-        bswap(value[2]),
-        bswap(value[3]),
-        bswap(value[4]),
-        bswap(value[5]),
-        bswap(value[6]),
-        bswap(value[7]),
-    ];
-    unsafe { core::mem::transmute::<_, [u8; 16]>(addr16) }
-}
diff --git a/tests/codegen/issues/issue-13018.rs b/tests/codegen/issues/issue-13018.rs
index a29452436d2c1..8040018b93106 100644
--- a/tests/codegen/issues/issue-13018.rs
+++ b/tests/codegen/issues/issue-13018.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 // A drop([...].clone()) sequence on an Rc should be a no-op
 // In particular, no call to __rust_dealloc should be emitted
diff --git a/tests/codegen/issues/issue-27130.rs b/tests/codegen/issues/issue-27130.rs
index 9c22b41e97fe3..594e02af0977f 100644
--- a/tests/codegen/issues/issue-27130.rs
+++ b/tests/codegen/issues/issue-27130.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-34634.rs b/tests/codegen/issues/issue-34634.rs
index a11f248e7404c..d32fa97ec38ce 100644
--- a/tests/codegen/issues/issue-34634.rs
+++ b/tests/codegen/issues/issue-34634.rs
@@ -3,7 +3,7 @@
 // switch case (the second check present until rustc 1.12).
 // This test also verifies that a single panic call is generated (for the division by zero case).
 
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 // CHECK-LABEL: @f
diff --git a/tests/codegen/issues/issue-34947-pow-i32.rs b/tests/codegen/issues/issue-34947-pow-i32.rs
index c9141c0e92521..b4750cd35bc34 100644
--- a/tests/codegen/issues/issue-34947-pow-i32.rs
+++ b/tests/codegen/issues/issue-34947-pow-i32.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-36010-some-box-is_some.rs b/tests/codegen/issues/issue-36010-some-box-is_some.rs
index 44c01096f15ae..c9a8262162d65 100644
--- a/tests/codegen/issues/issue-36010-some-box-is_some.rs
+++ b/tests/codegen/issues/issue-36010-some-box-is_some.rs
@@ -1,6 +1,6 @@
 #![crate_type = "lib"]
 
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 use std::mem;
 
diff --git a/tests/codegen/issues/issue-37945.rs b/tests/codegen/issues/issue-37945.rs
index 01d1c694ec7c6..23d0eab8ae466 100644
--- a/tests/codegen/issues/issue-37945.rs
+++ b/tests/codegen/issues/issue-37945.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Zmerge-functions=disabled
+//@ compile-flags: -Copt-level=3 -Zmerge-functions=disabled
 //@ ignore-32bit LLVM has a bug with them
 
 // Check that LLVM understands that `Iter` pointer is not null. Issue #37945.
diff --git a/tests/codegen/issues/issue-45222.rs b/tests/codegen/issues/issue-45222.rs
index d2c1ba421c45e..0201363c41aa6 100644
--- a/tests/codegen/issues/issue-45222.rs
+++ b/tests/codegen/issues/issue-45222.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-45466.rs b/tests/codegen/issues/issue-45466.rs
index 8a324fa555bb9..164a27ef5d4c4 100644
--- a/tests/codegen/issues/issue-45466.rs
+++ b/tests/codegen/issues/issue-45466.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "rlib"]
 
diff --git a/tests/codegen/issues/issue-45964-bounds-check-slice-pos.rs b/tests/codegen/issues/issue-45964-bounds-check-slice-pos.rs
index ea9288564e9d4..a48bb2a1ccf87 100644
--- a/tests/codegen/issues/issue-45964-bounds-check-slice-pos.rs
+++ b/tests/codegen/issues/issue-45964-bounds-check-slice-pos.rs
@@ -1,7 +1,7 @@
 // This test case checks that slice::{r}position functions do not
 // prevent optimizing away bounds checks
 
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "rlib"]
 
diff --git a/tests/codegen/issues/issue-59352.rs b/tests/codegen/issues/issue-59352.rs
index 7bedc3ffc4a1c..cb4383d4a309d 100644
--- a/tests/codegen/issues/issue-59352.rs
+++ b/tests/codegen/issues/issue-59352.rs
@@ -6,7 +6,7 @@
 // test case should be removed as it will become redundant.
 
 // mir-opt-level=3 enables inlining and enables LLVM to optimize away the unreachable panic call.
-//@ compile-flags: -O -Z mir-opt-level=3
+//@ compile-flags: -Copt-level=3 -Z mir-opt-level=3
 
 #![crate_type = "rlib"]
 
diff --git a/tests/codegen/issues/issue-68667-unwrap-combinators.rs b/tests/codegen/issues/issue-68667-unwrap-combinators.rs
index 21a5a5bf4ee94..7f4a32109fe9f 100644
--- a/tests/codegen/issues/issue-68667-unwrap-combinators.rs
+++ b/tests/codegen/issues/issue-68667-unwrap-combinators.rs
@@ -1,6 +1,6 @@
 #![crate_type = "lib"]
 
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 // MIR inlining now optimizes this code.
 
diff --git a/tests/codegen/issues/issue-69101-bounds-check.rs b/tests/codegen/issues/issue-69101-bounds-check.rs
index c014a1c1b1d43..953b79aa263e8 100644
--- a/tests/codegen/issues/issue-69101-bounds-check.rs
+++ b/tests/codegen/issues/issue-69101-bounds-check.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 // Make sure no bounds checks are emitted in the loop when upfront slicing
diff --git a/tests/codegen/issues/issue-73031.rs b/tests/codegen/issues/issue-73031.rs
index db9c6d6db2336..80dea9b5bc2b5 100644
--- a/tests/codegen/issues/issue-73031.rs
+++ b/tests/codegen/issues/issue-73031.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 // Test that LLVM can eliminate the unreachable `All::None` branch.
diff --git a/tests/codegen/issues/issue-73258.rs b/tests/codegen/issues/issue-73258.rs
index e5c622b5656b7..936a75544966b 100644
--- a/tests/codegen/issues/issue-73258.rs
+++ b/tests/codegen/issues/issue-73258.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-73396-bounds-check-after-position.rs b/tests/codegen/issues/issue-73396-bounds-check-after-position.rs
index 9b3b1318ced12..1e2c25babe0a5 100644
--- a/tests/codegen/issues/issue-73396-bounds-check-after-position.rs
+++ b/tests/codegen/issues/issue-73396-bounds-check-after-position.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 // Make sure no bounds checks are emitted when slicing or indexing
diff --git a/tests/codegen/issues/issue-73827-bounds-check-index-in-subexpr.rs b/tests/codegen/issues/issue-73827-bounds-check-index-in-subexpr.rs
index c3eb1a5968af4..e9dd0d1bf2378 100644
--- a/tests/codegen/issues/issue-73827-bounds-check-index-in-subexpr.rs
+++ b/tests/codegen/issues/issue-73827-bounds-check-index-in-subexpr.rs
@@ -1,7 +1,7 @@
 // This test checks that bounds checks are elided when
 // index is part of a (x | y) < C style condition
 
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-74938-array-split-at.rs b/tests/codegen/issues/issue-74938-array-split-at.rs
index 2675e404ced3b..9d3e23d642b8a 100644
--- a/tests/codegen/issues/issue-74938-array-split-at.rs
+++ b/tests/codegen/issues/issue-74938-array-split-at.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-75525-bounds-checks.rs b/tests/codegen/issues/issue-75525-bounds-checks.rs
index fbc10ce3d843e..5dfbd35001010 100644
--- a/tests/codegen/issues/issue-75525-bounds-checks.rs
+++ b/tests/codegen/issues/issue-75525-bounds-checks.rs
@@ -1,6 +1,6 @@
 // Regression test for #75525, verifies that no bounds checks are generated.
 
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-75546.rs b/tests/codegen/issues/issue-75546.rs
index 1132c8ab5093e..1e1e6543a889c 100644
--- a/tests/codegen/issues/issue-75546.rs
+++ b/tests/codegen/issues/issue-75546.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 // Test that LLVM can eliminate the impossible `i == 0` check.
diff --git a/tests/codegen/issues/issue-75659.rs b/tests/codegen/issues/issue-75659.rs
index 1860b73f2a9ad..0960bfdb6b0aa 100644
--- a/tests/codegen/issues/issue-75659.rs
+++ b/tests/codegen/issues/issue-75659.rs
@@ -1,7 +1,7 @@
 // This test checks that the call to memchr/slice_contains is optimized away
 // when searching in small slices.
 
-//@ compile-flags: -O -Zinline-mir=false
+//@ compile-flags: -Copt-level=3 -Zinline-mir=false
 //@ only-x86_64
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/issues/issue-75978.rs b/tests/codegen/issues/issue-75978.rs
index ed953fae76715..f4b0bc36329eb 100644
--- a/tests/codegen/issues/issue-75978.rs
+++ b/tests/codegen/issues/issue-75978.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-77812.rs b/tests/codegen/issues/issue-77812.rs
index bf84ac21b16d8..09e2376c30dda 100644
--- a/tests/codegen/issues/issue-77812.rs
+++ b/tests/codegen/issues/issue-77812.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 // Test that LLVM can eliminate the unreachable `Variant::Zero` branch.
diff --git a/tests/codegen/issues/issue-81408-dllimport-thinlto-windows.rs b/tests/codegen/issues/issue-81408-dllimport-thinlto-windows.rs
index 49301be776fdb..4023412f23cff 100644
--- a/tests/codegen/issues/issue-81408-dllimport-thinlto-windows.rs
+++ b/tests/codegen/issues/issue-81408-dllimport-thinlto-windows.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C lto=thin -C prefer-dynamic=no
+//@ compile-flags: -Copt-level=3 -C lto=thin -C prefer-dynamic=no
 //@ only-windows
 //@ aux-build:static_dllimport_aux.rs
 
diff --git a/tests/codegen/issues/issue-84268.rs b/tests/codegen/issues/issue-84268.rs
index 5e852133ed3d8..8a8ea9d1ccf8f 100644
--- a/tests/codegen/issues/issue-84268.rs
+++ b/tests/codegen/issues/issue-84268.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O --crate-type=rlib
+//@ compile-flags: -Copt-level=3 --crate-type=rlib
 #![feature(intrinsics, repr_simd)]
 
 extern "rust-intrinsic" {
diff --git a/tests/codegen/issues/issue-85872-multiple-reverse.rs b/tests/codegen/issues/issue-85872-multiple-reverse.rs
index fb5ff8309e5c5..6f566ddee6b02 100644
--- a/tests/codegen/issues/issue-85872-multiple-reverse.rs
+++ b/tests/codegen/issues/issue-85872-multiple-reverse.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-86109-eliminate-div-by-zero-check.rs b/tests/codegen/issues/issue-86109-eliminate-div-by-zero-check.rs
index a8fab61b13e92..345c09738b610 100644
--- a/tests/codegen/issues/issue-86109-eliminate-div-by-zero-check.rs
+++ b/tests/codegen/issues/issue-86109-eliminate-div-by-zero-check.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //! Test for https://github.com/rust-lang/rust/issues/86109
 //! Check LLVM can eliminate the impossible division by zero check by
 //! ensuring there is no call (to panic) instruction.
diff --git a/tests/codegen/issues/issue-93036-assert-index.rs b/tests/codegen/issues/issue-93036-assert-index.rs
index 7a2ea08726688..46f45c2f06ee7 100644
--- a/tests/codegen/issues/issue-93036-assert-index.rs
+++ b/tests/codegen/issues/issue-93036-assert-index.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-96274.rs b/tests/codegen/issues/issue-96274.rs
index ffefd5f43f8ca..2425ec53e4e19 100644
--- a/tests/codegen/issues/issue-96274.rs
+++ b/tests/codegen/issues/issue-96274.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-96497-slice-size-nowrap.rs b/tests/codegen/issues/issue-96497-slice-size-nowrap.rs
index f922462cc2790..dce156dd42541 100644
--- a/tests/codegen/issues/issue-96497-slice-size-nowrap.rs
+++ b/tests/codegen/issues/issue-96497-slice-size-nowrap.rs
@@ -2,7 +2,7 @@
 // The possibility of wrapping results in an additional branch when dropping boxed slices
 // in some situations, see https://github.com/rust-lang/rust/issues/96497#issuecomment-1112865218
 
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-98156-const-arg-temp-lifetime.rs b/tests/codegen/issues/issue-98156-const-arg-temp-lifetime.rs
index 28324bfa90ef3..aecb81caf22b1 100644
--- a/tests/codegen/issues/issue-98156-const-arg-temp-lifetime.rs
+++ b/tests/codegen/issues/issue-98156-const-arg-temp-lifetime.rs
@@ -1,6 +1,6 @@
 // This test checks that temporaries for indirectly-passed arguments get lifetime markers.
 
-//@ compile-flags: -O -C no-prepopulate-passes -Zmir-opt-level=0
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes -Zmir-opt-level=0
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-98294-get-mut-copy-from-slice-opt.rs b/tests/codegen/issues/issue-98294-get-mut-copy-from-slice-opt.rs
index 40827e32a0124..76adcf9fd4530 100644
--- a/tests/codegen/issues/issue-98294-get-mut-copy-from-slice-opt.rs
+++ b/tests/codegen/issues/issue-98294-get-mut-copy-from-slice-opt.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/issues/issue-99960.rs b/tests/codegen/issues/issue-99960.rs
index 9029121d35f49..571a9be967d49 100644
--- a/tests/codegen/issues/issue-99960.rs
+++ b/tests/codegen/issues/issue-99960.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/layout-size-checks.rs b/tests/codegen/layout-size-checks.rs
index 901f8f822f320..d64a7055e0b1e 100644
--- a/tests/codegen/layout-size-checks.rs
+++ b/tests/codegen/layout-size-checks.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ only-x86_64
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/lib-optimizations/iter-sum.rs b/tests/codegen/lib-optimizations/iter-sum.rs
index ea8c916bfc1b2..a054ffffe74bd 100644
--- a/tests/codegen/lib-optimizations/iter-sum.rs
+++ b/tests/codegen/lib-optimizations/iter-sum.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ only-x86_64 (vectorization varies between architectures)
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/lib-optimizations/slice_rotate.rs b/tests/codegen/lib-optimizations/slice_rotate.rs
index d0a7b328d1845..aa4bb3b528c96 100644
--- a/tests/codegen/lib-optimizations/slice_rotate.rs
+++ b/tests/codegen/lib-optimizations/slice_rotate.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/lifetime_start_end.rs b/tests/codegen/lifetime_start_end.rs
index 99d37c25dcac7..0639e7640aa15 100644
--- a/tests/codegen/lifetime_start_end.rs
+++ b/tests/codegen/lifetime_start_end.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C no-prepopulate-passes -Zmir-opt-level=0
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes -Zmir-opt-level=0
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/loads.rs b/tests/codegen/loads.rs
index e3e2f7577706b..88d67642b7250 100644
--- a/tests/codegen/loads.rs
+++ b/tests/codegen/loads.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -C no-prepopulate-passes -Zmir-opt-level=0 -O
+//@ compile-flags: -C no-prepopulate-passes -Zmir-opt-level=0 -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/loongarch-abi/loongarch64-lp64d-abi.rs b/tests/codegen/loongarch-abi/loongarch64-lp64d-abi.rs
index b147d01b38e32..b11bd657c18ec 100644
--- a/tests/codegen/loongarch-abi/loongarch64-lp64d-abi.rs
+++ b/tests/codegen/loongarch-abi/loongarch64-lp64d-abi.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C no-prepopulate-passes --target loongarch64-unknown-linux-gnu
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes --target loongarch64-unknown-linux-gnu
 //@ needs-llvm-components: loongarch
 
 #![feature(no_core, lang_items)]
diff --git a/tests/codegen/lto-removes-invokes.rs b/tests/codegen/lto-removes-invokes.rs
index 3217c239bf789..3640bd1ab8652 100644
--- a/tests/codegen/lto-removes-invokes.rs
+++ b/tests/codegen/lto-removes-invokes.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -C lto -C panic=abort -O
+//@ compile-flags: -C lto -C panic=abort -Copt-level=3
 //@ no-prefer-dynamic
 
 fn main() {
diff --git a/tests/codegen/macos/i686-macosx-deployment-target.rs b/tests/codegen/macos/i686-macosx-deployment-target.rs
index 389434da1f67d..1f44bdfc6485e 100644
--- a/tests/codegen/macos/i686-macosx-deployment-target.rs
+++ b/tests/codegen/macos/i686-macosx-deployment-target.rs
@@ -2,7 +2,7 @@
 // Checks that we correctly modify the target when MACOSX_DEPLOYMENT_TARGET is set.
 // See issue #60235.
 
-//@ compile-flags: -O --target=i686-apple-darwin --crate-type=rlib
+//@ compile-flags: -Copt-level=3 --target=i686-apple-darwin --crate-type=rlib
 //@ needs-llvm-components: x86
 //@ rustc-env:MACOSX_DEPLOYMENT_TARGET=10.14
 #![feature(no_core, lang_items)]
diff --git a/tests/codegen/macos/i686-no-macosx-deployment-target.rs b/tests/codegen/macos/i686-no-macosx-deployment-target.rs
index 4c6b7656e5937..a09773e0b9e26 100644
--- a/tests/codegen/macos/i686-no-macosx-deployment-target.rs
+++ b/tests/codegen/macos/i686-no-macosx-deployment-target.rs
@@ -2,7 +2,7 @@
 // Checks that we leave the target alone MACOSX_DEPLOYMENT_TARGET is unset.
 // See issue #60235.
 
-//@ compile-flags: -O --target=i686-apple-darwin --crate-type=rlib
+//@ compile-flags: -Copt-level=3 --target=i686-apple-darwin --crate-type=rlib
 //@ needs-llvm-components: x86
 //@ unset-rustc-env:MACOSX_DEPLOYMENT_TARGET
 #![feature(no_core, lang_items)]
diff --git a/tests/codegen/macos/x86_64-macosx-deployment-target.rs b/tests/codegen/macos/x86_64-macosx-deployment-target.rs
index a40deca24bbeb..bd8c027a9fb9d 100644
--- a/tests/codegen/macos/x86_64-macosx-deployment-target.rs
+++ b/tests/codegen/macos/x86_64-macosx-deployment-target.rs
@@ -2,7 +2,7 @@
 // Checks that we correctly modify the target when MACOSX_DEPLOYMENT_TARGET is set.
 // See issue #60235.
 
-//@ compile-flags: -O --target=x86_64-apple-darwin --crate-type=rlib
+//@ compile-flags: -Copt-level=3 --target=x86_64-apple-darwin --crate-type=rlib
 //@ needs-llvm-components: x86
 //@ rustc-env:MACOSX_DEPLOYMENT_TARGET=10.14
 #![feature(no_core, lang_items)]
diff --git a/tests/codegen/macos/x86_64-no-macosx-deployment-target.rs b/tests/codegen/macos/x86_64-no-macosx-deployment-target.rs
index 26d519ef1a6dc..ff4a8fc46f984 100644
--- a/tests/codegen/macos/x86_64-no-macosx-deployment-target.rs
+++ b/tests/codegen/macos/x86_64-no-macosx-deployment-target.rs
@@ -2,7 +2,7 @@
 // Checks that we leave the target alone when MACOSX_DEPLOYMENT_TARGET is unset.
 // See issue #60235.
 
-//@ compile-flags: -O --target=x86_64-apple-darwin --crate-type=rlib
+//@ compile-flags: -Copt-level=3 --target=x86_64-apple-darwin --crate-type=rlib
 //@ needs-llvm-components: x86
 //@ unset-rustc-env:MACOSX_DEPLOYMENT_TARGET
 #![feature(no_core, lang_items)]
diff --git a/tests/codegen/match-optimized.rs b/tests/codegen/match-optimized.rs
index d6893be0b7bef..7b409e619a8c5 100644
--- a/tests/codegen/match-optimized.rs
+++ b/tests/codegen/match-optimized.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -C no-prepopulate-passes -O
+//@ compile-flags: -Cno-prepopulate-passes -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/match-optimizes-away.rs b/tests/codegen/match-optimizes-away.rs
index 82ab5718b3750..8a70d99342316 100644
--- a/tests/codegen/match-optimizes-away.rs
+++ b/tests/codegen/match-optimizes-away.rs
@@ -1,5 +1,5 @@
 //
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 pub enum Three {
diff --git a/tests/codegen/maybeuninit-rvo.rs b/tests/codegen/maybeuninit-rvo.rs
index db2e33c34bd25..097aa610f1b34 100644
--- a/tests/codegen/maybeuninit-rvo.rs
+++ b/tests/codegen/maybeuninit-rvo.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ needs-unwind
 #![feature(c_unwind)]
 #![crate_type = "lib"]
diff --git a/tests/codegen/mem-replace-simple-type.rs b/tests/codegen/mem-replace-simple-type.rs
index 41c3660dc15c0..9f3c6bacb712c 100644
--- a/tests/codegen/mem-replace-simple-type.rs
+++ b/tests/codegen/mem-replace-simple-type.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C no-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes
 //@ only-x86_64 (to not worry about usize differing)
 //@ ignore-std-debug-assertions
 // Reason: precondition checks make mem::replace not a candidate for MIR inlining
diff --git a/tests/codegen/merge-functions.rs b/tests/codegen/merge-functions.rs
index 8e4b65c9ee65c..b9d3727ce112e 100644
--- a/tests/codegen/merge-functions.rs
+++ b/tests/codegen/merge-functions.rs
@@ -1,6 +1,6 @@
 //@ revisions: O Os
 //@[Os] compile-flags: -Copt-level=s
-//@[O] compile-flags: -O
+//@[O] compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 // CHECK: @func{{2|1}} = {{.*}}alias{{.*}}@func{{1|2}}
diff --git a/tests/codegen/mir-aggregate-no-alloca.rs b/tests/codegen/mir-aggregate-no-alloca.rs
index 37b024a55b373..77d367ed5da9e 100644
--- a/tests/codegen/mir-aggregate-no-alloca.rs
+++ b/tests/codegen/mir-aggregate-no-alloca.rs
@@ -2,7 +2,7 @@
 //@ revisions: bit32 bit64
 //@[bit32] only-32bit
 //@[bit64] only-64bit
-//@ compile-flags: -O -C no-prepopulate-passes -Z randomize-layout=no
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes -Z randomize-layout=no
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/mir-inlined-line-numbers.rs b/tests/codegen/mir-inlined-line-numbers.rs
index 57978bc709765..cfe43a6cf89ac 100644
--- a/tests/codegen/mir-inlined-line-numbers.rs
+++ b/tests/codegen/mir-inlined-line-numbers.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -g
+//@ compile-flags: -Copt-level=3 -g
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/move-before-nocapture-ref-arg.rs b/tests/codegen/move-before-nocapture-ref-arg.rs
index c3448192ea173..2ebd645e1c3d0 100644
--- a/tests/codegen/move-before-nocapture-ref-arg.rs
+++ b/tests/codegen/move-before-nocapture-ref-arg.rs
@@ -1,6 +1,6 @@
 // Verify that move before the call of the function with noalias, nocapture, readonly.
 // #107436
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/move-operands.rs b/tests/codegen/move-operands.rs
index 4f22921b4a3dc..ddad231b762cd 100644
--- a/tests/codegen/move-operands.rs
+++ b/tests/codegen/move-operands.rs
@@ -1,5 +1,5 @@
 // Verify that optimized MIR only copies `a` once.
-//@ compile-flags: -O -C no-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/naked-fn/generics.rs b/tests/codegen/naked-fn/generics.rs
index a33d213617a8b..64998df64ddb6 100644
--- a/tests/codegen/naked-fn/generics.rs
+++ b/tests/codegen/naked-fn/generics.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ only-x86_64
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/noalias-box-off.rs b/tests/codegen/noalias-box-off.rs
index 1642103903a0b..664c79502804e 100644
--- a/tests/codegen/noalias-box-off.rs
+++ b/tests/codegen/noalias-box-off.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Z box-noalias=no
+//@ compile-flags: -Copt-level=3 -Z box-noalias=no
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/noalias-box.rs b/tests/codegen/noalias-box.rs
index 06f94691c8956..cccde775977a1 100644
--- a/tests/codegen/noalias-box.rs
+++ b/tests/codegen/noalias-box.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/noalias-flag.rs b/tests/codegen/noalias-flag.rs
index 35b94d813d5fb..67ba68ee6f80a 100644
--- a/tests/codegen/noalias-flag.rs
+++ b/tests/codegen/noalias-flag.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Zmutable-noalias=no
+//@ compile-flags: -Copt-level=3 -Zmutable-noalias=no
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/noalias-refcell.rs b/tests/codegen/noalias-refcell.rs
index 51d13967bece6..b37adf92b9cc3 100644
--- a/tests/codegen/noalias-refcell.rs
+++ b/tests/codegen/noalias-refcell.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C no-prepopulate-passes -Z mutable-noalias=yes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes -Z mutable-noalias=yes
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/noalias-rwlockreadguard.rs b/tests/codegen/noalias-rwlockreadguard.rs
index 7b870cb28b4fc..c676dc32399da 100644
--- a/tests/codegen/noalias-rwlockreadguard.rs
+++ b/tests/codegen/noalias-rwlockreadguard.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C no-prepopulate-passes -Z mutable-noalias=yes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes -Z mutable-noalias=yes
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/noalias-unpin.rs b/tests/codegen/noalias-unpin.rs
index 630a62020c11d..30a8b399b9798 100644
--- a/tests/codegen/noalias-unpin.rs
+++ b/tests/codegen/noalias-unpin.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Z mutable-noalias=yes
+//@ compile-flags: -Copt-level=3 -Z mutable-noalias=yes
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/nrvo.rs b/tests/codegen/nrvo.rs
index aa8bed941f545..7972186bfe5d1 100644
--- a/tests/codegen/nrvo.rs
+++ b/tests/codegen/nrvo.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/option-as-slice.rs b/tests/codegen/option-as-slice.rs
index 0edbbac11762d..39b34a2035b74 100644
--- a/tests/codegen/option-as-slice.rs
+++ b/tests/codegen/option-as-slice.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Z randomize-layout=no
+//@ compile-flags: -Copt-level=3 -Z randomize-layout=no
 //@ only-x86_64
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/option-niche-eq.rs b/tests/codegen/option-niche-eq.rs
index caef0598b4bed..9c5ed9ce57a5e 100644
--- a/tests/codegen/option-niche-eq.rs
+++ b/tests/codegen/option-niche-eq.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Zmerge-functions=disabled
+//@ compile-flags: -Copt-level=3 -Zmerge-functions=disabled
 #![crate_type = "lib"]
 
 extern crate core;
diff --git a/tests/codegen/packed.rs b/tests/codegen/packed.rs
index 66df978d48ca2..6f62719282eac 100644
--- a/tests/codegen/packed.rs
+++ b/tests/codegen/packed.rs
@@ -1,5 +1,5 @@
 //
-//@ compile-flags: -O -C no-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/panic-abort-windows.rs b/tests/codegen/panic-abort-windows.rs
index eb61e649f04a2..17fdd9cc72609 100644
--- a/tests/codegen/panic-abort-windows.rs
+++ b/tests/codegen/panic-abort-windows.rs
@@ -1,7 +1,7 @@
 // This test is for *-windows only.
 //@ only-windows
 
-//@ compile-flags: -C no-prepopulate-passes -C panic=abort -O
+//@ compile-flags: -C no-prepopulate-passes -C panic=abort -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/panic-in-drop-abort.rs b/tests/codegen/panic-in-drop-abort.rs
index b150c537ad550..e89170e56ed08 100644
--- a/tests/codegen/panic-in-drop-abort.rs
+++ b/tests/codegen/panic-in-drop-abort.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -Z panic-in-drop=abort -O
+//@ compile-flags: -Z panic-in-drop=abort -Copt-level=3
 //@ ignore-msvc
 
 // Ensure that unwinding code paths are eliminated from the output after
diff --git a/tests/codegen/personality_lifetimes.rs b/tests/codegen/personality_lifetimes.rs
index 828af05436b42..cd81db6395349 100644
--- a/tests/codegen/personality_lifetimes.rs
+++ b/tests/codegen/personality_lifetimes.rs
@@ -1,7 +1,7 @@
 //@ ignore-msvc
 //@ needs-unwind
 
-//@ compile-flags: -O -C no-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/placement-new.rs b/tests/codegen/placement-new.rs
index 0ec2b6a6f20e7..7f7f0033bece3 100644
--- a/tests/codegen/placement-new.rs
+++ b/tests/codegen/placement-new.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ compile-flags: -Zmerge-functions=disabled
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/ptr-arithmetic.rs b/tests/codegen/ptr-arithmetic.rs
index 6f115d33d8ddf..ecb44b30f5cad 100644
--- a/tests/codegen/ptr-arithmetic.rs
+++ b/tests/codegen/ptr-arithmetic.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Z merge-functions=disabled
+//@ compile-flags: -Copt-level=3 -Z merge-functions=disabled
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/ptr-read-metadata.rs b/tests/codegen/ptr-read-metadata.rs
index e3565c962f738..b38cfdbff8835 100644
--- a/tests/codegen/ptr-read-metadata.rs
+++ b/tests/codegen/ptr-read-metadata.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Z merge-functions=disabled
+//@ compile-flags: -Copt-level=3 -Z merge-functions=disabled
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/range-attribute.rs b/tests/codegen/range-attribute.rs
index a44ec1026b164..e23f5e6bb748a 100644
--- a/tests/codegen/range-attribute.rs
+++ b/tests/codegen/range-attribute.rs
@@ -5,7 +5,7 @@
 //@ revisions: bit32 bit64
 //@[bit32] only-32bit
 //@[bit64] only-64bit
-//@ compile-flags: -O -C no-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes
 //@ min-llvm-version: 19
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/range_to_inclusive.rs b/tests/codegen/range_to_inclusive.rs
index f3001897f88d9..6d939f40f5582 100644
--- a/tests/codegen/range_to_inclusive.rs
+++ b/tests/codegen/range_to_inclusive.rs
@@ -1,6 +1,6 @@
 //! Test that `RangeTo` and `RangeToInclusive` generate identical
 //! (and optimal) code; #63646
-//@ compile-flags: -O -Zmerge-functions=disabled
+//@ compile-flags: -Copt-level=3 -Zmerge-functions=disabled
 #![crate_type = "lib"]
 
 #[no_mangle]
diff --git a/tests/codegen/reg-struct-return.rs b/tests/codegen/reg-struct-return.rs
index 73816745ea86d..dfc9f8c519c2a 100644
--- a/tests/codegen/reg-struct-return.rs
+++ b/tests/codegen/reg-struct-return.rs
@@ -5,7 +5,7 @@
 
 //@ revisions: ENABLED DISABLED
 //@ add-core-stubs
-//@ compile-flags: --target i686-unknown-linux-gnu -O -C no-prepopulate-passes
+//@ compile-flags: --target i686-unknown-linux-gnu -Cno-prepopulate-passes -Copt-level=3
 //@ [ENABLED] compile-flags: -Zreg-struct-return
 //@ needs-llvm-components: x86
 
diff --git a/tests/codegen/regparm-inreg.rs b/tests/codegen/regparm-inreg.rs
index c8c647bcc87c0..82e157311287a 100644
--- a/tests/codegen/regparm-inreg.rs
+++ b/tests/codegen/regparm-inreg.rs
@@ -2,7 +2,7 @@
 // marks function arguments as "inreg" like the C/C++ compilers for the platforms.
 // x86 only.
 
-//@ compile-flags: --target i686-unknown-linux-gnu -O -C no-prepopulate-passes
+//@ compile-flags: --target i686-unknown-linux-gnu -Cno-prepopulate-passes -Copt-level=3
 //@ needs-llvm-components: x86
 
 //@ revisions:regparm0 regparm1 regparm2 regparm3
diff --git a/tests/codegen/repeat-trusted-len.rs b/tests/codegen/repeat-trusted-len.rs
index fa01f2b4969d6..95379535971f2 100644
--- a/tests/codegen/repeat-trusted-len.rs
+++ b/tests/codegen/repeat-trusted-len.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/repr/transparent-byval-struct-ptr.rs b/tests/codegen/repr/transparent-byval-struct-ptr.rs
index 92ef937d734b4..f9cfeb90390c9 100644
--- a/tests/codegen/repr/transparent-byval-struct-ptr.rs
+++ b/tests/codegen/repr/transparent-byval-struct-ptr.rs
@@ -1,5 +1,5 @@
 //@ revisions: i686-linux i686-freebsd x64-linux x64-apple
-//@ compile-flags: -O -C no-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes
 
 //@[i686-linux] compile-flags: --target i686-unknown-linux-gnu
 //@[i686-linux] needs-llvm-components: x86
diff --git a/tests/codegen/repr/transparent-imm-array.rs b/tests/codegen/repr/transparent-imm-array.rs
index 99828e4e80a5f..f790d093cf4a8 100644
--- a/tests/codegen/repr/transparent-imm-array.rs
+++ b/tests/codegen/repr/transparent-imm-array.rs
@@ -1,5 +1,5 @@
 //@ revisions: arm-linux arm-android armv7-linux armv7-android mips thumb sparc
-//@ compile-flags: -O -C no-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes
 
 //@[arm-linux] compile-flags: --target arm-unknown-linux-gnueabi
 //@[arm-linux] needs-llvm-components: arm
diff --git a/tests/codegen/repr/transparent-mips64.rs b/tests/codegen/repr/transparent-mips64.rs
index 588d440b4d7bf..7282654b8562d 100644
--- a/tests/codegen/repr/transparent-mips64.rs
+++ b/tests/codegen/repr/transparent-mips64.rs
@@ -1,5 +1,5 @@
 //@ revisions: mips64 mips64el
-//@ compile-flags: -O -C no-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes
 
 //@[mips64] compile-flags: --target mips64-unknown-linux-gnuabi64
 //@[mips64] needs-llvm-components: mips
diff --git a/tests/codegen/repr/transparent-opaque-ptr.rs b/tests/codegen/repr/transparent-opaque-ptr.rs
index 29c03f0d5d96f..798b7e01bba5b 100644
--- a/tests/codegen/repr/transparent-opaque-ptr.rs
+++ b/tests/codegen/repr/transparent-opaque-ptr.rs
@@ -1,5 +1,5 @@
 //@ revisions: aarch64-linux aarch64-darwin wasm32-wasip1
-//@ compile-flags: -O -C no-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes
 
 //@[aarch64-linux] compile-flags: --target aarch64-unknown-linux-gnu
 //@[aarch64-linux] needs-llvm-components: aarch64
diff --git a/tests/codegen/repr/transparent-sparc64.rs b/tests/codegen/repr/transparent-sparc64.rs
index 8e4c8ce2ee9b1..05c090bd67215 100644
--- a/tests/codegen/repr/transparent-sparc64.rs
+++ b/tests/codegen/repr/transparent-sparc64.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C no-prepopulate-passes --target sparc64-unknown-linux-gnu
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes --target sparc64-unknown-linux-gnu
 //@ needs-llvm-components: sparc
 
 // See ./transparent.rs
diff --git a/tests/codegen/repr/transparent-sysv64.rs b/tests/codegen/repr/transparent-sysv64.rs
index 068414976c523..99c855db96200 100644
--- a/tests/codegen/repr/transparent-sysv64.rs
+++ b/tests/codegen/repr/transparent-sysv64.rs
@@ -1,5 +1,5 @@
 //@ revisions: linux apple win
-//@ compile-flags: -O -C no-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes
 
 //@[linux] compile-flags: --target x86_64-unknown-linux-gnu
 //@[linux] needs-llvm-components: x86
diff --git a/tests/codegen/repr/transparent.rs b/tests/codegen/repr/transparent.rs
index adcd3aacd2ace..e7e4c40a09917 100644
--- a/tests/codegen/repr/transparent.rs
+++ b/tests/codegen/repr/transparent.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C no-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes
 //@ ignore-riscv64 riscv64 has an i128 type used with test_Vector
 //@ ignore-s390x s390x with default march passes vector types per reference
 //@ ignore-loongarch64 see codegen/loongarch-abi for loongarch function call tests
diff --git a/tests/codegen/riscv-abi/riscv64-lp64-lp64f-lp64d-abi.rs b/tests/codegen/riscv-abi/riscv64-lp64-lp64f-lp64d-abi.rs
index 520192b5d5915..46f747ad40750 100644
--- a/tests/codegen/riscv-abi/riscv64-lp64-lp64f-lp64d-abi.rs
+++ b/tests/codegen/riscv-abi/riscv64-lp64-lp64f-lp64d-abi.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: --target riscv64gc-unknown-linux-gnu -O -C no-prepopulate-passes -C panic=abort
+//@ compile-flags: --target riscv64gc-unknown-linux-gnu -Copt-level=3 -C no-prepopulate-passes -C panic=abort
 //@ needs-llvm-components: riscv
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/riscv-abi/riscv64-lp64d-abi.rs b/tests/codegen/riscv-abi/riscv64-lp64d-abi.rs
index c14d5c01450bc..bef8fe0c04418 100644
--- a/tests/codegen/riscv-abi/riscv64-lp64d-abi.rs
+++ b/tests/codegen/riscv-abi/riscv64-lp64d-abi.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C no-prepopulate-passes --target riscv64gc-unknown-linux-gnu
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes --target riscv64gc-unknown-linux-gnu
 //@ needs-llvm-components: riscv
 
 #![feature(no_core, lang_items)]
diff --git a/tests/codegen/riscv-abi/riscv64-lp64f-lp64d-abi.rs b/tests/codegen/riscv-abi/riscv64-lp64f-lp64d-abi.rs
index 27018d2e6d203..214370f424c25 100644
--- a/tests/codegen/riscv-abi/riscv64-lp64f-lp64d-abi.rs
+++ b/tests/codegen/riscv-abi/riscv64-lp64f-lp64d-abi.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C no-prepopulate-passes --target riscv64gc-unknown-linux-gnu
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes --target riscv64gc-unknown-linux-gnu
 //@ needs-llvm-components: riscv
 
 #![feature(no_core, lang_items)]
diff --git a/tests/codegen/rust-abi-arch-specific-adjustment.rs b/tests/codegen/rust-abi-arch-specific-adjustment.rs
index 9da10f662b0e6..561f081c700ea 100644
--- a/tests/codegen/rust-abi-arch-specific-adjustment.rs
+++ b/tests/codegen/rust-abi-arch-specific-adjustment.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C no-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes
 //@ revisions: riscv64 loongarch64
 
 //@[riscv64] only-riscv64
diff --git a/tests/codegen/s390x-simd.rs b/tests/codegen/s390x-simd.rs
index 23181e6a10308..ac39357519e4c 100644
--- a/tests/codegen/s390x-simd.rs
+++ b/tests/codegen/s390x-simd.rs
@@ -1,7 +1,7 @@
 //! test that s390x vector types are passed using `PassMode::Direct`
 //! see also https://github.com/rust-lang/rust/issues/135744
 //@ add-core-stubs
-//@ compile-flags: --target s390x-unknown-linux-gnu -O
+//@ compile-flags: --target s390x-unknown-linux-gnu -Copt-level=3
 //@ needs-llvm-components: systemz
 
 #![crate_type = "rlib"]
diff --git a/tests/codegen/scalar-pair-bool.rs b/tests/codegen/scalar-pair-bool.rs
index fce0648e45074..def3b32f71aa4 100644
--- a/tests/codegen/scalar-pair-bool.rs
+++ b/tests/codegen/scalar-pair-bool.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/simd/swap-simd-types.rs b/tests/codegen/simd/swap-simd-types.rs
index cd6e84286e1c9..69767d0a75580 100644
--- a/tests/codegen/simd/swap-simd-types.rs
+++ b/tests/codegen/simd/swap-simd-types.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C target-feature=+avx
+//@ compile-flags: -Copt-level=3 -C target-feature=+avx
 //@ only-x86_64
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/slice-as_chunks.rs b/tests/codegen/slice-as_chunks.rs
index 631d18d780951..a90ee7c628ece 100644
--- a/tests/codegen/slice-as_chunks.rs
+++ b/tests/codegen/slice-as_chunks.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ only-64bit (because the LLVM type of i64 for usize shows up)
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/slice-indexing.rs b/tests/codegen/slice-indexing.rs
index 75112bb0c24e5..d957ccfb5ef7d 100644
--- a/tests/codegen/slice-indexing.rs
+++ b/tests/codegen/slice-indexing.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ only-64bit (because the LLVM type of i64 for usize shows up)
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/slice-iter-fold.rs b/tests/codegen/slice-iter-fold.rs
index 1770cd4a11994..55ab34661c36e 100644
--- a/tests/codegen/slice-iter-fold.rs
+++ b/tests/codegen/slice-iter-fold.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 // CHECK-LABEL: @slice_fold_to_last
diff --git a/tests/codegen/slice-iter-len-eq-zero.rs b/tests/codegen/slice-iter-len-eq-zero.rs
index b2a4b2495b6a2..c85861d47f852 100644
--- a/tests/codegen/slice-iter-len-eq-zero.rs
+++ b/tests/codegen/slice-iter-len-eq-zero.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 type Demo = [u8; 3];
diff --git a/tests/codegen/slice-iter-nonnull.rs b/tests/codegen/slice-iter-nonnull.rs
index 307020b42c06f..98a1b961a6443 100644
--- a/tests/codegen/slice-iter-nonnull.rs
+++ b/tests/codegen/slice-iter-nonnull.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ needs-deterministic-layouts
 #![crate_type = "lib"]
 #![feature(exact_size_is_empty)]
diff --git a/tests/codegen/slice-pointer-nonnull-unwrap.rs b/tests/codegen/slice-pointer-nonnull-unwrap.rs
index 202edb98c7329..35e4bf2c6615f 100644
--- a/tests/codegen/slice-pointer-nonnull-unwrap.rs
+++ b/tests/codegen/slice-pointer-nonnull-unwrap.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 use std::ptr::NonNull;
diff --git a/tests/codegen/slice-position-bounds-check.rs b/tests/codegen/slice-position-bounds-check.rs
index f83e2f2ec440e..0d1d1d869ae25 100644
--- a/tests/codegen/slice-position-bounds-check.rs
+++ b/tests/codegen/slice-position-bounds-check.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C panic=abort
+//@ compile-flags: -Copt-level=3 -C panic=abort
 #![crate_type = "lib"]
 
 fn search<T: Ord + Eq>(arr: &mut [T], a: &T) -> Result<usize, ()> {
diff --git a/tests/codegen/slice-ref-equality.rs b/tests/codegen/slice-ref-equality.rs
index 1153d7817b278..a5046a7594458 100644
--- a/tests/codegen/slice-ref-equality.rs
+++ b/tests/codegen/slice-ref-equality.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Zmerge-functions=disabled
+//@ compile-flags: -Copt-level=3 -Zmerge-functions=disabled
 #![crate_type = "lib"]
 
 use std::num::NonZero;
diff --git a/tests/codegen/slice-reverse.rs b/tests/codegen/slice-reverse.rs
index 87cdad479628a..e58d1c1d9d8ea 100644
--- a/tests/codegen/slice-reverse.rs
+++ b/tests/codegen/slice-reverse.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ only-x86_64
 //@ ignore-std-debug-assertions (debug assertions prevent generating shufflevector)
 
diff --git a/tests/codegen/slice-windows-no-bounds-check.rs b/tests/codegen/slice-windows-no-bounds-check.rs
index db3211c8defdb..87e89b14f06c8 100644
--- a/tests/codegen/slice-windows-no-bounds-check.rs
+++ b/tests/codegen/slice-windows-no-bounds-check.rs
@@ -1,6 +1,6 @@
 #![crate_type = "lib"]
 
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 use std::slice::Windows;
 
diff --git a/tests/codegen/slice_as_from_ptr_range.rs b/tests/codegen/slice_as_from_ptr_range.rs
index 47c60461c0e81..2073f05c07f0c 100644
--- a/tests/codegen/slice_as_from_ptr_range.rs
+++ b/tests/codegen/slice_as_from_ptr_range.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ only-64bit (because we're using [ui]size)
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/some-global-nonnull.rs b/tests/codegen/some-global-nonnull.rs
index 8e9308a726582..bb4d12e1c7621 100644
--- a/tests/codegen/some-global-nonnull.rs
+++ b/tests/codegen/some-global-nonnull.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/sparc-struct-abi.rs b/tests/codegen/sparc-struct-abi.rs
index 5d9781663570a..0a8720c4fcae3 100644
--- a/tests/codegen/sparc-struct-abi.rs
+++ b/tests/codegen/sparc-struct-abi.rs
@@ -1,7 +1,7 @@
 // Checks that we correctly codegen extern "C" functions returning structs.
 // See issues #52638 and #86163.
 
-//@ compile-flags: -O --target=sparc64-unknown-linux-gnu --crate-type=rlib
+//@ compile-flags: -Copt-level=3 --target=sparc64-unknown-linux-gnu --crate-type=rlib
 //@ needs-llvm-components: sparc
 #![feature(no_core, lang_items)]
 #![no_core]
diff --git a/tests/codegen/static-relocation-model-msvc.rs b/tests/codegen/static-relocation-model-msvc.rs
index 8ed8331466c73..4d30e6ec505d4 100644
--- a/tests/codegen/static-relocation-model-msvc.rs
+++ b/tests/codegen/static-relocation-model-msvc.rs
@@ -1,6 +1,6 @@
 // Verify linkage of external symbols in the static relocation model on MSVC.
 //
-//@ compile-flags: -O -C relocation-model=static
+//@ compile-flags: -Copt-level=3 -C relocation-model=static
 //@ aux-build: extern_decl.rs
 //@ only-x86_64-pc-windows-msvc
 
diff --git a/tests/codegen/step_by-overflow-checks.rs b/tests/codegen/step_by-overflow-checks.rs
index 43e8514a8b7c2..53800e9f879d9 100644
--- a/tests/codegen/step_by-overflow-checks.rs
+++ b/tests/codegen/step_by-overflow-checks.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/swap-large-types.rs b/tests/codegen/swap-large-types.rs
index 761d48969dad9..49a41bb14692f 100644
--- a/tests/codegen/swap-large-types.rs
+++ b/tests/codegen/swap-large-types.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ only-x86_64
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/swap-small-types.rs b/tests/codegen/swap-small-types.rs
index 1a48c63d8139f..76bb853e64238 100644
--- a/tests/codegen/swap-small-types.rs
+++ b/tests/codegen/swap-small-types.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Z merge-functions=disabled
+//@ compile-flags: -Copt-level=3 -Z merge-functions=disabled
 //@ only-x86_64
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/thread-local.rs b/tests/codegen/thread-local.rs
index 3cd81652f5ace..9ce34473b9150 100644
--- a/tests/codegen/thread-local.rs
+++ b/tests/codegen/thread-local.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ aux-build:thread_local_aux.rs
 //@ ignore-windows FIXME(#134939)
 //@ ignore-wasm globals are used instead of thread locals
diff --git a/tests/codegen/to_vec.rs b/tests/codegen/to_vec.rs
index 4666f8d6f1532..4f6e77188d81b 100644
--- a/tests/codegen/to_vec.rs
+++ b/tests/codegen/to_vec.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/trailing_zeros.rs b/tests/codegen/trailing_zeros.rs
index b659e061821ea..0816a98099269 100644
--- a/tests/codegen/trailing_zeros.rs
+++ b/tests/codegen/trailing_zeros.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/transmute-optimized.rs b/tests/codegen/transmute-optimized.rs
index de54eecf0c049..477fdc6de90d4 100644
--- a/tests/codegen/transmute-optimized.rs
+++ b/tests/codegen/transmute-optimized.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Z merge-functions=disabled
+//@ compile-flags: -Copt-level=3 -Z merge-functions=disabled
 #![crate_type = "lib"]
 
 // This tests that LLVM can optimize based on the niches in the source or
diff --git a/tests/codegen/try_question_mark_nop.rs b/tests/codegen/try_question_mark_nop.rs
index 36a0d9066c895..751d7ca931160 100644
--- a/tests/codegen/try_question_mark_nop.rs
+++ b/tests/codegen/try_question_mark_nop.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Z merge-functions=disabled --edition=2021
+//@ compile-flags: -Copt-level=3 -Z merge-functions=disabled --edition=2021
 //@ only-x86_64
 // FIXME: Remove the `min-llvm-version`.
 //@ revisions: NINETEEN TWENTY
diff --git a/tests/codegen/ub-checks.rs b/tests/codegen/ub-checks.rs
index de48d74e652f1..67f5bff08d5bb 100644
--- a/tests/codegen/ub-checks.rs
+++ b/tests/codegen/ub-checks.rs
@@ -8,7 +8,7 @@
 //@ revisions: DEBUG NOCHECKS
 //@ [DEBUG] compile-flags:
 //@ [NOCHECKS] compile-flags: -Zub-checks=no
-//@ compile-flags: -O -Cdebug-assertions=yes
+//@ compile-flags: -Copt-level=3 -Cdebug-assertions=yes
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/unchecked_shifts.rs b/tests/codegen/unchecked_shifts.rs
index 86517c896276d..b27eb73c0cc94 100644
--- a/tests/codegen/unchecked_shifts.rs
+++ b/tests/codegen/unchecked_shifts.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 #![feature(unchecked_shifts)]
diff --git a/tests/codegen/union-abi.rs b/tests/codegen/union-abi.rs
index 2f14682dfa57c..92d40d8ac14cb 100644
--- a/tests/codegen/union-abi.rs
+++ b/tests/codegen/union-abi.rs
@@ -1,5 +1,5 @@
 //@ ignore-emscripten vectors passed directly
-//@ compile-flags: -O -C no-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes
 // 32-bit x86 returns `f32` differently to avoid the x87 stack.
 // 32-bit systems will return 128bit values using a return area pointer.
 //@ revisions: x86 bit32 bit64
diff --git a/tests/codegen/var-names.rs b/tests/codegen/var-names.rs
index 4ea5b3b436d81..40720e197614e 100644
--- a/tests/codegen/var-names.rs
+++ b/tests/codegen/var-names.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -C no-prepopulate-passes
+//@ compile-flags: -Copt-level=3 -C no-prepopulate-passes
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/vec-as-ptr.rs b/tests/codegen/vec-as-ptr.rs
index 17869c21c8321..5c997802640d2 100644
--- a/tests/codegen/vec-as-ptr.rs
+++ b/tests/codegen/vec-as-ptr.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Zmerge-functions=disabled
+//@ compile-flags: -Copt-level=3 -Zmerge-functions=disabled
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/vec-calloc.rs b/tests/codegen/vec-calloc.rs
index f88ed7ae8a555..2e2769ce1301a 100644
--- a/tests/codegen/vec-calloc.rs
+++ b/tests/codegen/vec-calloc.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Z merge-functions=disabled
+//@ compile-flags: -Copt-level=3 -Z merge-functions=disabled
 //@ only-x86_64
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/vec-in-place.rs b/tests/codegen/vec-in-place.rs
index e835a7ef69bd8..1f6836f6dfabb 100644
--- a/tests/codegen/vec-in-place.rs
+++ b/tests/codegen/vec-in-place.rs
@@ -1,5 +1,5 @@
 //@ ignore-std-debug-assertions (FIXME: checks for call detect scoped noalias metadata)
-//@ compile-flags: -O -Z merge-functions=disabled
+//@ compile-flags: -Copt-level=3 -Z merge-functions=disabled
 #![crate_type = "lib"]
 
 // Ensure that trivial casts of vec elements are O(1)
diff --git a/tests/codegen/vec-iter-collect-len.rs b/tests/codegen/vec-iter-collect-len.rs
index 8c5d2f6f9a74f..a88573522d4d8 100644
--- a/tests/codegen/vec-iter-collect-len.rs
+++ b/tests/codegen/vec-iter-collect-len.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 #[no_mangle]
diff --git a/tests/codegen/vec-iter.rs b/tests/codegen/vec-iter.rs
index 310680969c4fe..4ed00d2d34f0b 100644
--- a/tests/codegen/vec-iter.rs
+++ b/tests/codegen/vec-iter.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 #![feature(exact_size_is_empty)]
 
diff --git a/tests/codegen/vec-len-invariant.rs b/tests/codegen/vec-len-invariant.rs
index 780c86bab9569..033181c2bfb72 100644
--- a/tests/codegen/vec-len-invariant.rs
+++ b/tests/codegen/vec-len-invariant.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ only-64bit
 //
 // This test confirms that we do not reload the length of a Vec after growing it in push.
diff --git a/tests/codegen/vec-optimizes-away.rs b/tests/codegen/vec-optimizes-away.rs
index 77a94b0b4294a..39d5c1614c82a 100644
--- a/tests/codegen/vec-optimizes-away.rs
+++ b/tests/codegen/vec-optimizes-away.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 #![crate_type = "lib"]
 
 #[no_mangle]
diff --git a/tests/codegen/vec-reserve-extend.rs b/tests/codegen/vec-reserve-extend.rs
index 1f00f7d206339..4d3f23ccecfc8 100644
--- a/tests/codegen/vec-reserve-extend.rs
+++ b/tests/codegen/vec-reserve-extend.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/vec-shrink-panik.rs b/tests/codegen/vec-shrink-panik.rs
index 873904c2569e4..23dd300d48cd6 100644
--- a/tests/codegen/vec-shrink-panik.rs
+++ b/tests/codegen/vec-shrink-panik.rs
@@ -1,6 +1,6 @@
 // LLVM 17 realizes double panic is not possible and doesn't generate calls
 // to panic_cannot_unwind.
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ ignore-std-debug-assertions (plain old debug assertions)
 //@ needs-unwind
 #![crate_type = "lib"]
diff --git a/tests/codegen/vec-with-capacity.rs b/tests/codegen/vec-with-capacity.rs
index e8c5bc88bd0db..777bbcc4fcb47 100644
--- a/tests/codegen/vec-with-capacity.rs
+++ b/tests/codegen/vec-with-capacity.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ ignore-std-debug-assertions
 // (with debug assertions turned on, `assert_unchecked` generates a real assertion)
 
diff --git a/tests/codegen/vec_pop_push_noop.rs b/tests/codegen/vec_pop_push_noop.rs
index 4821e84088408..2635660596ab1 100644
--- a/tests/codegen/vec_pop_push_noop.rs
+++ b/tests/codegen/vec_pop_push_noop.rs
@@ -1,7 +1,7 @@
 //@ revisions: llvm-pre-19 llvm-19
 //@ [llvm-19] min-llvm-version: 19
 //@ [llvm-pre-19] max-llvm-major-version: 18
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/vecdeque-drain.rs b/tests/codegen/vecdeque-drain.rs
index 8a34ba0674b1b..a5e5da6501332 100644
--- a/tests/codegen/vecdeque-drain.rs
+++ b/tests/codegen/vecdeque-drain.rs
@@ -1,6 +1,6 @@
 // Check that draining at the front or back doesn't copy memory.
 
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ needs-deterministic-layouts
 //@ ignore-std-debug-assertions (FIXME: checks for call detect scoped noalias metadata)
 
diff --git a/tests/codegen/vecdeque-nonempty-get-no-panic.rs b/tests/codegen/vecdeque-nonempty-get-no-panic.rs
index 3f802de9eeed7..1f886b096bbbf 100644
--- a/tests/codegen/vecdeque-nonempty-get-no-panic.rs
+++ b/tests/codegen/vecdeque-nonempty-get-no-panic.rs
@@ -1,6 +1,6 @@
 // Guards against regression for optimization discussed in issue #80836
 
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/vecdeque_no_panic.rs b/tests/codegen/vecdeque_no_panic.rs
index da948d12254cd..3166842afca0e 100644
--- a/tests/codegen/vecdeque_no_panic.rs
+++ b/tests/codegen/vecdeque_no_panic.rs
@@ -1,6 +1,6 @@
 // This test checks that `VecDeque::front[_mut]()` and `VecDeque::back[_mut]()` can't panic.
 
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 //@ ignore-std-debug-assertions (plain old debug assertions)
 
 #![crate_type = "lib"]
diff --git a/tests/codegen/vecdeque_pop_push.rs b/tests/codegen/vecdeque_pop_push.rs
index 040d5a279dcab..5afa1b2248b0e 100644
--- a/tests/codegen/vecdeque_pop_push.rs
+++ b/tests/codegen/vecdeque_pop_push.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/virtual-function-elimination-32bit.rs b/tests/codegen/virtual-function-elimination-32bit.rs
index 76223be1f3dad..c9919cecccf9b 100644
--- a/tests/codegen/virtual-function-elimination-32bit.rs
+++ b/tests/codegen/virtual-function-elimination-32bit.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -Zvirtual-function-elimination -Clto -O -Csymbol-mangling-version=v0
+//@ compile-flags: -Zvirtual-function-elimination -Clto -Copt-level=3 -Csymbol-mangling-version=v0
 //@ ignore-64bit
 
 // CHECK: @vtable.0 = {{.*}}, !type ![[TYPE0:[0-9]+]], !vcall_visibility ![[VCALL_VIS0:[0-9]+]]
diff --git a/tests/codegen/virtual-function-elimination.rs b/tests/codegen/virtual-function-elimination.rs
index 23d7657baa99b..d2d0c4b78abd1 100644
--- a/tests/codegen/virtual-function-elimination.rs
+++ b/tests/codegen/virtual-function-elimination.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -Zvirtual-function-elimination -Clto -O -Csymbol-mangling-version=v0
+//@ compile-flags: -Zvirtual-function-elimination -Clto -Copt-level=3 -Csymbol-mangling-version=v0
 //@ ignore-32bit
 
 // CHECK: @vtable.0 = {{.*}}, !type ![[TYPE0:[0-9]+]], !vcall_visibility ![[VCALL_VIS0:[0-9]+]]
diff --git a/tests/codegen/vtable-loads.rs b/tests/codegen/vtable-loads.rs
index 1dd6ca51063b1..aa103ec6f7cb8 100644
--- a/tests/codegen/vtable-loads.rs
+++ b/tests/codegen/vtable-loads.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O
+//@ compile-flags: -Copt-level=3
 
 #![crate_type = "lib"]
 
diff --git a/tests/codegen/zip.rs b/tests/codegen/zip.rs
index ea8caba61f396..38ecf7c15c675 100644
--- a/tests/codegen/zip.rs
+++ b/tests/codegen/zip.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -C no-prepopulate-passes -O
+//@ compile-flags: -Cno-prepopulate-passes -Copt-level=3
 
 #![crate_type = "lib"]