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[MemoryLocation][DSE] Allow other read effects in MemoryLocation::getForDest() (#144343)

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MemoryLocation::getForDest() returns a (potentially) written location,
while still allowing other reads. Currently, this is limited to
argmemonly functions. However, we can ignore other (non-argmem) read
effects here for the same reason we can ignore argument reads.
    
Fixes https://github.com/llvm/llvm-project/issues/144300.

Proof: https://alive2.llvm.org/ce/z/LKq_dc
This commit is contained in:
Nikita Popov
2025-06-17 09:49:18 +02:00
committed by GitHub
parent 80b79ce432
commit bb70023cbf
2 changed files with 35 additions and 1 deletions
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4
llvm/lib/Analysis/MemoryLocation.cpp
View File

@@ -111,7 +111,9 @@ MemoryLocation MemoryLocation::getForDest(const AnyMemIntrinsic *MI) {
std::optional<MemoryLocation>
MemoryLocation::getForDest(const CallBase *CB, const TargetLibraryInfo &TLI) {
if (!CB->onlyAccessesArgMemory())
// Check that the only possible writes are to arguments.
MemoryEffects WriteME = CB->getMemoryEffects() & MemoryEffects::writeOnly();
if (!WriteME.onlyAccessesArgPointees())
return std::nullopt;
if (CB->hasOperandBundles())

32
llvm/test/Transforms/DeadStoreElimination/trivial-dse-calls.ll
View File

@@ -286,3 +286,35 @@ define void @test_dse_non_alloca() {
ret void
}
define void @test_other_read_effects() {
; CHECK-LABEL: @test_other_read_effects(
; CHECK-NEXT: ret void
;
%a = alloca i32, align 4
call void @f(ptr %a) memory(read, argmem: readwrite) nounwind willreturn
ret void
}
define i32 @test_other_read_effects_read_after() {
; CHECK-LABEL: @test_other_read_effects_read_after(
; CHECK-NEXT: [[A:%.*]] = alloca i32, align 4
; CHECK-NEXT: call void @f(ptr [[A]]) #[[ATTR5:[0-9]+]]
; CHECK-NEXT: [[V:%.*]] = load i32, ptr [[A]], align 4
; CHECK-NEXT: ret i32 [[V]]
;
%a = alloca i32, align 4
call void @f(ptr %a) memory(read, argmem: readwrite) nounwind willreturn
%v = load i32, ptr %a
ret i32 %v
}
define void @test_other_write_effects() {
; CHECK-LABEL: @test_other_write_effects(
; CHECK-NEXT: [[A:%.*]] = alloca i32, align 4
; CHECK-NEXT: call void @f(ptr [[A]]) #[[ATTR6:[0-9]+]]
; CHECK-NEXT: ret void
;
%a = alloca i32, align 4
call void @f(ptr %a) memory(write, argmem: readwrite) nounwind willreturn
ret void
}