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[EVM] Support non-precise memory locations in VM AliasAnalysis #900

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[EVM] Support non-precise memory locations in VM AliasAnalysis #900

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19 changes: 18 additions & 1 deletion llvm/lib/Analysis/VMAliasAnalysis.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -112,7 +112,7 @@ AliasResult VMAAResult::alias(const MemoryLocation &LocA,
return AAResultBase::alias(LocA, LocB, AAQI, I);

// Don't check unknown memory locations.
if (!LocA.Size.isPrecise() || !LocB.Size.isPrecise())
if (!LocA.Size.isPrecise() && !LocB.Size.isPrecise())
return AAResultBase::alias(LocA, LocB, AAQI, I);

// Only 256-bit keys are valid for storage.
Expand Down Expand Up @@ -166,6 +166,23 @@ AliasResult VMAAResult::alias(const MemoryLocation &LocA,
return AliasResult::PartialAlias;
}

// If one of the locations is imprecise, they don’t alias as long as
// the other location is precise and ends before the first one begins.
if (LocB.Size == LocationSize::afterPointer()) {
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@akiramenai akiramenai Oct 2, 2025 •
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Maintainability: I suggest to refactor that code (including DoesOverlap lambda). We have code duplication right below this if, and returning NoAlias, PartialAlias based on a predicate is also become a duplicate.

if (StartBVal.sge(StartAVal + LocA.Size.getValue()))
return AliasResult::NoAlias;
return AliasResult::PartialAlias;
}

if (LocA.Size == LocationSize::afterPointer()) {
if (StartAVal.sge(StartBVal + LocB.Size.getValue()))
return AliasResult::NoAlias;
return AliasResult::PartialAlias;
}

if (!LocA.Size.isPrecise() || !LocB.Size.isPrecise())
return AAResultBase::alias(LocA, LocB, AAQI, I);

auto DoesOverlap = [](const APInt &X, const APInt &XEnd, const APInt &Y) {
return Y.sge(X) && Y.slt(XEnd);
};
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17 changes: 17 additions & 0 deletions llvm/test/CodeGen/EVM/aa-eval.ll
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Expand Up @@ -471,3 +471,20 @@ define void @test_as1_alias_extcodecopy() {
call void @llvm.evm.extcodecopy(i256 0, ptr addrspace(1) null, ptr addrspace(4) null, i256 32)
ret void
}

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Redundant


; CHECK-LABEL: Function: test_as1_alias_return_nonprecise
; CHECK: NoModRef: Ptr: i256* inttoptr (i256 32 to ptr addrspace(1)) <-> call void @llvm.evm.return
define void @test_as1_alias_return_nonprecise(i256 %size) noreturn {
store i256 1, ptr addrspace(1) inttoptr (i256 32 to ptr addrspace(1)), align 32
call void @llvm.evm.return(ptr addrspace(1) inttoptr (i256 128 to ptr addrspace(1)), i256 %size)
unreachable
}

; CHECK-LABEL: Function: test_as1_part_alias_return_nonprecise
; CHECK: Just Ref: Ptr: i256* inttoptr (i256 100 to ptr addrspace(1)) <-> call void @llvm.evm.return
define void @test_as1_part_alias_return_nonprecise(i256 %size) noreturn {
store i256 1, ptr addrspace(1) inttoptr (i256 100 to ptr addrspace(1)), align 32
call void @llvm.evm.return(ptr addrspace(1) inttoptr (i256 128 to ptr addrspace(1)), i256 %size)
unreachable
}
72 changes: 72 additions & 0 deletions llvm/test/CodeGen/EVM/evm-dse-non-precise-memloc.ll
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@@ -0,0 +1,72 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt -O3 -S < %s | FileCheck %s
target datalayout = "E-p:256:256-i256:256:256-S256-a:256:256"
target triple = "evm"

; This test verifies that the dead store to (i256 32 to ptr addrspace(1)) is eliminated.

declare i256 @llvm.evm.datasize(metadata) #0

declare i256 @llvm.evm.dataoffset(metadata) #0

declare i256 @llvm.evm.callvalue() #1

declare void @llvm.evm.return(ptr addrspace(1) readonly, i256) #2

declare void @llvm.evm.revert(ptr addrspace(1) readonly, i256) #3

declare void @llvm.memcpy.p1.p4.i256(ptr addrspace(1) noalias nocapture writeonly, ptr addrspace(4) noalias nocapture readonly, i256, i1 immarg) #4

define void @__entry() local_unnamed_addr #5 {
; CHECK-LABEL: define void @__entry(
; CHECK-SAME: ) local_unnamed_addr #[[ATTR5:[0-9]+]] {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: store i256 129, ptr addrspace(1) inttoptr (i256 100 to ptr addrspace(1)), align 64
; CHECK-NEXT: [[CALLVALUE:%.*]] = tail call i256 @llvm.evm.callvalue()
; CHECK-NEXT: [[IF_CONDITION_COMPARED_NOT:%.*]] = icmp eq i256 [[CALLVALUE]], 0
; CHECK-NEXT: br i1 [[IF_CONDITION_COMPARED_NOT]], label %[[IF_JOIN:.*]], label %[[IF_MAIN:.*]]
; CHECK: [[IF_MAIN]]:
; CHECK-NEXT: tail call void @llvm.evm.revert(ptr addrspace(1) noalias nocapture nofree noundef nonnull align 32 null, i256 32)
; CHECK-NEXT: unreachable
; CHECK: [[IF_JOIN]]:
; CHECK-NEXT: store i256 42, ptr addrspace(5) null, align 4294967296
; CHECK-NEXT: [[DATASIZE:%.*]] = tail call i256 @llvm.evm.datasize(metadata [[META0:![0-9]+]])
; CHECK-NEXT: [[DATAOFFSET:%.*]] = tail call i256 @llvm.evm.dataoffset(metadata [[META0]])
; CHECK-NEXT: [[CODECOPY_SOURCE_POINTER:%.*]] = inttoptr i256 [[DATAOFFSET]] to ptr addrspace(4)
; CHECK-NEXT: tail call void @llvm.memcpy.p1.p4.i256(ptr addrspace(1) nonnull align 128 inttoptr (i256 128 to ptr addrspace(1)), ptr addrspace(4) align 1 [[CODECOPY_SOURCE_POINTER]], i256 [[DATASIZE]], i1 false)
; CHECK-NEXT: tail call void @llvm.evm.return(ptr addrspace(1) noalias nocapture nofree noundef nonnull align 32 inttoptr (i256 128 to ptr addrspace(1)), i256 [[DATASIZE]])
; CHECK-NEXT: unreachable
;
entry:
; To be removed
store i256 128, ptr addrspace(1) inttoptr (i256 32 to ptr addrspace(1)), align 64
store i256 129, ptr addrspace(1) inttoptr (i256 100 to ptr addrspace(1)), align 64
%callvalue = tail call i256 @llvm.evm.callvalue()
%if_condition_compared.not = icmp eq i256 %callvalue, 0
br i1 %if_condition_compared.not, label %if_join, label %if_main

if_main:
tail call void @llvm.evm.revert(ptr addrspace(1) noalias nocapture nofree noundef nonnull align 32 null, i256 32)
unreachable

if_join:
store i256 42, ptr addrspace(5) null, align 4294967296
%datasize = tail call i256 @llvm.evm.datasize(metadata !0)
%dataoffset = tail call i256 @llvm.evm.dataoffset(metadata !0)
%codecopy_source_pointer = inttoptr i256 %dataoffset to ptr addrspace(4)
tail call void @llvm.memcpy.p1.p4.i256(ptr addrspace(1) nonnull align 128 inttoptr (i256 128 to ptr addrspace(1)), ptr addrspace(4) align 1 %codecopy_source_pointer, i256 %datasize, i1 false)
tail call void @llvm.evm.return(ptr addrspace(1) noalias nocapture nofree noundef nonnull align 32 inttoptr (i256 128 to ptr addrspace(1)), i256 %datasize)
unreachable
}

attributes #0 = { mustprogress nocallback nofree nosync nounwind willreturn memory(none) }
attributes #1 = { mustprogress nofree nosync nounwind willreturn memory(none) }
attributes #2 = { nofree noreturn nounwind memory(read) }
attributes #3 = { nofree noreturn nounwind memory(argmem: read) }
attributes #4 = { mustprogress nocallback nofree nounwind willreturn memory(argmem: readwrite) }
attributes #5 = { nofree noreturn nounwind null_pointer_is_valid memory(readwrite, inaccessiblemem: read) "evm-entry-function" }

!0 = !{!"Test_16_deployed"}
;.
; CHECK: [[META0]] = !{!"Test_16_deployed"}
;.
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