Rollup merge of rust-lang#132319 - Zalathar:add-module-flag, r=jieyouxu

cg_llvm: Clean up FFI calls for setting module flags

This is a combination of several inter-related changes to how module flags are set:

- Remove some unnecessary code for setting an `"LTOPostLink"` flag, which has been obsolete since LLVM 17.
- Define our own enum instead of relying on enum values defined by LLVM's unstable C++ API.
- Use safe wrapper functions to set module flags, instead of direct `unsafe` calls.
- Consistently pass pointer/length strings instead of C strings.
- Remove or shrink some `unsafe` blocks.

Author: matthiaskrgr

compiler/rustc_codegen_llvm/src/back/lto.rs

@@ -25,7 +25,6 @@ use tracing::{debug, info};
 use crate::back::write::{
     self, CodegenDiagnosticsStage, DiagnosticHandlers, bitcode_section_name, save_temp_bitcode,
 };
-use crate::common::AsCCharPtr;
 use crate::errors::{
     DynamicLinkingWithLTO, LlvmError, LtoBitcodeFromRlib, LtoDisallowed, LtoDylib, LtoProcMacro,
 };
@@ -602,23 +601,9 @@ pub(crate) fn run_pass_manager(
     // This code is based off the code found in llvm's LTO code generator:
     //      llvm/lib/LTO/LTOCodeGenerator.cpp
     debug!("running the pass manager");
-    unsafe {
-        if !llvm::LLVMRustHasModuleFlag(
-            module.module_llvm.llmod(),
-            "LTOPostLink".as_c_char_ptr(),
-            11,
-        ) {
-            llvm::LLVMRustAddModuleFlagU32(
-                module.module_llvm.llmod(),
-                llvm::LLVMModFlagBehavior::Error,
-                c"LTOPostLink".as_ptr(),
-                1,
-            );
-        }
-        let opt_stage = if thin { llvm::OptStage::ThinLTO } else { llvm::OptStage::FatLTO };
-        let opt_level = config.opt_level.unwrap_or(config::OptLevel::No);
-        write::llvm_optimize(cgcx, dcx, module, config, opt_level, opt_stage)?;
-    }
+    let opt_stage = if thin { llvm::OptStage::ThinLTO } else { llvm::OptStage::FatLTO };
+    let opt_level = config.opt_level.unwrap_or(config::OptLevel::No);
+    unsafe { write::llvm_optimize(cgcx, dcx, module, config, opt_level, opt_stage) }?;
     debug!("lto done");
     Ok(())
 }

compiler/rustc_codegen_llvm/src/context.rs

@@ -210,133 +210,111 @@ pub(crate) unsafe fn create_module<'ll>(
     // If skipping the PLT is enabled, we need to add some module metadata
     // to ensure intrinsic calls don't use it.
     if !sess.needs_plt() {
-        let avoid_plt = c"RtLibUseGOT".as_ptr();
-        unsafe {
-            llvm::LLVMRustAddModuleFlagU32(llmod, llvm::LLVMModFlagBehavior::Warning, avoid_plt, 1);
-        }
+        llvm::add_module_flag_u32(llmod, llvm::ModuleFlagMergeBehavior::Warning, "RtLibUseGOT", 1);
     }
 
     // Enable canonical jump tables if CFI is enabled. (See https://reviews.llvm.org/D65629.)
     if sess.is_sanitizer_cfi_canonical_jump_tables_enabled() && sess.is_sanitizer_cfi_enabled() {
-        let canonical_jump_tables = c"CFI Canonical Jump Tables".as_ptr();
-        unsafe {
-            llvm::LLVMRustAddModuleFlagU32(
-                llmod,
-                llvm::LLVMModFlagBehavior::Override,
-                canonical_jump_tables,
-                1,
-            );
-        }
+        llvm::add_module_flag_u32(
+            llmod,
+            llvm::ModuleFlagMergeBehavior::Override,
+            "CFI Canonical Jump Tables",
+            1,
+        );
     }
 
     // If we're normalizing integers with CFI, ensure LLVM generated functions do the same.
     // See https://github.com/llvm/llvm-project/pull/104826
     if sess.is_sanitizer_cfi_normalize_integers_enabled() {
-        let cfi_normalize_integers = c"cfi-normalize-integers".as_ptr();
-        unsafe {
-            llvm::LLVMRustAddModuleFlagU32(
-                llmod,
-                llvm::LLVMModFlagBehavior::Override,
-                cfi_normalize_integers,
-                1,
-            );
-        }
+        llvm::add_module_flag_u32(
+            llmod,
+            llvm::ModuleFlagMergeBehavior::Override,
+            "cfi-normalize-integers",
+            1,
+        );
     }
 
     // Enable LTO unit splitting if specified or if CFI is enabled. (See
     // https://reviews.llvm.org/D53891.)
     if sess.is_split_lto_unit_enabled() || sess.is_sanitizer_cfi_enabled() {
-        let enable_split_lto_unit = c"EnableSplitLTOUnit".as_ptr();
-        unsafe {
-            llvm::LLVMRustAddModuleFlagU32(
-                llmod,
-                llvm::LLVMModFlagBehavior::Override,
-                enable_split_lto_unit,
-                1,
-            );
-        }
+        llvm::add_module_flag_u32(
+            llmod,
+            llvm::ModuleFlagMergeBehavior::Override,
+            "EnableSplitLTOUnit",
+            1,
+        );
     }
 
     // Add "kcfi" module flag if KCFI is enabled. (See https://reviews.llvm.org/D119296.)
     if sess.is_sanitizer_kcfi_enabled() {
-        let kcfi = c"kcfi".as_ptr();
-        unsafe {
-            llvm::LLVMRustAddModuleFlagU32(llmod, llvm::LLVMModFlagBehavior::Override, kcfi, 1);
-        }
+        llvm::add_module_flag_u32(llmod, llvm::ModuleFlagMergeBehavior::Override, "kcfi", 1);
 
         // Add "kcfi-offset" module flag with -Z patchable-function-entry (See
         // https://reviews.llvm.org/D141172).
         let pfe =
             PatchableFunctionEntry::from_config(sess.opts.unstable_opts.patchable_function_entry);
         if pfe.prefix() > 0 {
-            let kcfi_offset = c"kcfi-offset".as_ptr();
-            unsafe {
-                llvm::LLVMRustAddModuleFlagU32(
-                    llmod,
-                    llvm::LLVMModFlagBehavior::Override,
-                    kcfi_offset,
-                    pfe.prefix().into(),
-                );
-            }
+            llvm::add_module_flag_u32(
+                llmod,
+                llvm::ModuleFlagMergeBehavior::Override,
+                "kcfi-offset",
+                pfe.prefix().into(),
+            );
         }
     }
 
     // Control Flow Guard is currently only supported by the MSVC linker on Windows.
     if sess.target.is_like_msvc {
-        unsafe {
-            match sess.opts.cg.control_flow_guard {
-                CFGuard::Disabled => {}
-                CFGuard::NoChecks => {
-                    // Set `cfguard=1` module flag to emit metadata only.
-                    llvm::LLVMRustAddModuleFlagU32(
-                        llmod,
-                        llvm::LLVMModFlagBehavior::Warning,
-                        c"cfguard".as_ptr() as *const _,
-                        1,
-                    )
-                }
-                CFGuard::Checks => {
-                    // Set `cfguard=2` module flag to emit metadata and checks.
-                    llvm::LLVMRustAddModuleFlagU32(
-                        llmod,
-                        llvm::LLVMModFlagBehavior::Warning,
-                        c"cfguard".as_ptr() as *const _,
-                        2,
-                    )
-                }
+        match sess.opts.cg.control_flow_guard {
+            CFGuard::Disabled => {}
+            CFGuard::NoChecks => {
+                // Set `cfguard=1` module flag to emit metadata only.
+                llvm::add_module_flag_u32(
+                    llmod,
+                    llvm::ModuleFlagMergeBehavior::Warning,
+                    "cfguard",
+                    1,
+                );
+            }
+            CFGuard::Checks => {
+                // Set `cfguard=2` module flag to emit metadata and checks.
+                llvm::add_module_flag_u32(
+                    llmod,
+                    llvm::ModuleFlagMergeBehavior::Warning,
+                    "cfguard",
+                    2,
+                );
             }
         }
     }
 
     if let Some(BranchProtection { bti, pac_ret }) = sess.opts.unstable_opts.branch_protection {
         if sess.target.arch == "aarch64" {
-            unsafe {
-                llvm::LLVMRustAddModuleFlagU32(
-                    llmod,
-                    llvm::LLVMModFlagBehavior::Min,
-                    c"branch-target-enforcement".as_ptr(),
-                    bti.into(),
-                );
-                llvm::LLVMRustAddModuleFlagU32(
-                    llmod,
-                    llvm::LLVMModFlagBehavior::Min,
-                    c"sign-return-address".as_ptr(),
-                    pac_ret.is_some().into(),
-                );
-                let pac_opts = pac_ret.unwrap_or(PacRet { leaf: false, key: PAuthKey::A });
-                llvm::LLVMRustAddModuleFlagU32(
-                    llmod,
-                    llvm::LLVMModFlagBehavior::Min,
-                    c"sign-return-address-all".as_ptr(),
-                    pac_opts.leaf.into(),
-                );
-                llvm::LLVMRustAddModuleFlagU32(
-                    llmod,
-                    llvm::LLVMModFlagBehavior::Min,
-                    c"sign-return-address-with-bkey".as_ptr(),
-                    u32::from(pac_opts.key == PAuthKey::B),
-                );
-            }
+            llvm::add_module_flag_u32(
+                llmod,
+                llvm::ModuleFlagMergeBehavior::Min,
+                "branch-target-enforcement",
+                bti.into(),
+            );
+            llvm::add_module_flag_u32(
+                llmod,
+                llvm::ModuleFlagMergeBehavior::Min,
+                "sign-return-address",
+                pac_ret.is_some().into(),
+            );
+            let pac_opts = pac_ret.unwrap_or(PacRet { leaf: false, key: PAuthKey::A });
+            llvm::add_module_flag_u32(
+                llmod,
+                llvm::ModuleFlagMergeBehavior::Min,
+                "sign-return-address-all",
+                pac_opts.leaf.into(),
+            );
+            llvm::add_module_flag_u32(
+                llmod,
+                llvm::ModuleFlagMergeBehavior::Min,
+                "sign-return-address-with-bkey",
+                u32::from(pac_opts.key == PAuthKey::B),
+            );
         } else {
             bug!(
                 "branch-protection used on non-AArch64 target; \
@@ -347,75 +325,59 @@ pub(crate) unsafe fn create_module<'ll>(
 
     // Pass on the control-flow protection flags to LLVM (equivalent to `-fcf-protection` in Clang).
     if let CFProtection::Branch | CFProtection::Full = sess.opts.unstable_opts.cf_protection {
-        unsafe {
-            llvm::LLVMRustAddModuleFlagU32(
-                llmod,
-                llvm::LLVMModFlagBehavior::Override,
-                c"cf-protection-branch".as_ptr(),
-                1,
-            );
-        }
+        llvm::add_module_flag_u32(
+            llmod,
+            llvm::ModuleFlagMergeBehavior::Override,
+            "cf-protection-branch",
+            1,
+        );
     }
     if let CFProtection::Return | CFProtection::Full = sess.opts.unstable_opts.cf_protection {
-        unsafe {
-            llvm::LLVMRustAddModuleFlagU32(
-                llmod,
-                llvm::LLVMModFlagBehavior::Override,
-                c"cf-protection-return".as_ptr(),
-                1,
-            );
-        }
+        llvm::add_module_flag_u32(
+            llmod,
+            llvm::ModuleFlagMergeBehavior::Override,
+            "cf-protection-return",
+            1,
+        );
     }
 
     if sess.opts.unstable_opts.virtual_function_elimination {
-        unsafe {
-            llvm::LLVMRustAddModuleFlagU32(
-                llmod,
-                llvm::LLVMModFlagBehavior::Error,
-                c"Virtual Function Elim".as_ptr(),
-                1,
-            );
-        }
+        llvm::add_module_flag_u32(
+            llmod,
+            llvm::ModuleFlagMergeBehavior::Error,
+            "Virtual Function Elim",
+            1,
+        );
     }
 
     // Set module flag to enable Windows EHCont Guard (/guard:ehcont).
     if sess.opts.unstable_opts.ehcont_guard {
-        unsafe {
-            llvm::LLVMRustAddModuleFlagU32(
-                llmod,
-                llvm::LLVMModFlagBehavior::Warning,
-                c"ehcontguard".as_ptr() as *const _,
-                1,
-            )
-        }
+        llvm::add_module_flag_u32(llmod, llvm::ModuleFlagMergeBehavior::Warning, "ehcontguard", 1);
     }
 
     match sess.opts.unstable_opts.function_return {
         FunctionReturn::Keep => {}
-        FunctionReturn::ThunkExtern => unsafe {
-            llvm::LLVMRustAddModuleFlagU32(
+        FunctionReturn::ThunkExtern => {
+            llvm::add_module_flag_u32(
                 llmod,
-                llvm::LLVMModFlagBehavior::Override,
-                c"function_return_thunk_extern".as_ptr(),
+                llvm::ModuleFlagMergeBehavior::Override,
+                "function_return_thunk_extern",
                 1,
-            )
-        },
+            );
+        }
     }
 
     match (sess.opts.unstable_opts.small_data_threshold, sess.target.small_data_threshold_support())
     {
         // Set up the small-data optimization limit for architectures that use
         // an LLVM module flag to control this.
         (Some(threshold), SmallDataThresholdSupport::LlvmModuleFlag(flag)) => {
-            let flag = SmallCStr::new(flag.as_ref());
-            unsafe {
-                llvm::LLVMRustAddModuleFlagU32(
-                    llmod,
-                    llvm::LLVMModFlagBehavior::Error,
-                    flag.as_c_str().as_ptr(),
-                    threshold as u32,
-                )
-            }
+            llvm::add_module_flag_u32(
+                llmod,
+                llvm::ModuleFlagMergeBehavior::Error,
+                &flag,
+                threshold as u32,
+            );
         }
         _ => (),
     };
@@ -449,33 +411,29 @@ pub(crate) unsafe fn create_module<'ll>(
     // If llvm_abiname is empty, emit nothing.
     let llvm_abiname = &sess.target.options.llvm_abiname;
     if matches!(sess.target.arch.as_ref(), "riscv32" | "riscv64") && !llvm_abiname.is_empty() {
-        unsafe {
-            llvm::LLVMRustAddModuleFlagString(
-                llmod,
-                llvm::LLVMModFlagBehavior::Error,
-                c"target-abi".as_ptr(),
-                llvm_abiname.as_c_char_ptr(),
-                llvm_abiname.len(),
-            );
-        }
+        llvm::add_module_flag_str(
+            llmod,
+            llvm::ModuleFlagMergeBehavior::Error,
+            "target-abi",
+            llvm_abiname,
+        );
     }
 
     // Add module flags specified via -Z llvm_module_flag
-    for (key, value, behavior) in &sess.opts.unstable_opts.llvm_module_flag {
-        let key = format!("{key}\0");
-        let behavior = match behavior.as_str() {
-            "error" => llvm::LLVMModFlagBehavior::Error,
-            "warning" => llvm::LLVMModFlagBehavior::Warning,
-            "require" => llvm::LLVMModFlagBehavior::Require,
-            "override" => llvm::LLVMModFlagBehavior::Override,
-            "append" => llvm::LLVMModFlagBehavior::Append,
-            "appendunique" => llvm::LLVMModFlagBehavior::AppendUnique,
-            "max" => llvm::LLVMModFlagBehavior::Max,
-            "min" => llvm::LLVMModFlagBehavior::Min,
+    for (key, value, merge_behavior) in &sess.opts.unstable_opts.llvm_module_flag {
+        let merge_behavior = match merge_behavior.as_str() {
+            "error" => llvm::ModuleFlagMergeBehavior::Error,
+            "warning" => llvm::ModuleFlagMergeBehavior::Warning,
+            "require" => llvm::ModuleFlagMergeBehavior::Require,
+            "override" => llvm::ModuleFlagMergeBehavior::Override,
+            "append" => llvm::ModuleFlagMergeBehavior::Append,
+            "appendunique" => llvm::ModuleFlagMergeBehavior::AppendUnique,
+            "max" => llvm::ModuleFlagMergeBehavior::Max,
+            "min" => llvm::ModuleFlagMergeBehavior::Min,
             // We already checked this during option parsing
             _ => unreachable!(),
         };
-        unsafe { llvm::LLVMRustAddModuleFlagU32(llmod, behavior, key.as_c_char_ptr(), *value) }
+        llvm::add_module_flag_u32(llmod, merge_behavior, key, *value);
     }
 
     llmod