[MemoryLocation][DSE] Allow other read effects in MemoryLocation::getForDest() #144343
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…ForDest() 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 llvm#144300.
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@llvm/pr-subscribers-llvm-transforms Author: Nikita Popov (nikic) ChangesMemoryLocation::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 #144300. Full diff: https://github.com/llvm/llvm-project/pull/144343.diff 2 Files Affected:
diff --git a/llvm/lib/Analysis/MemoryLocation.cpp b/llvm/lib/Analysis/MemoryLocation.cpp
index 3b42bb412b9ba..c8daab7abde18 100644
--- a/llvm/lib/Analysis/MemoryLocation.cpp
+++ b/llvm/lib/Analysis/MemoryLocation.cpp
@@ -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())
diff --git a/llvm/test/Transforms/DeadStoreElimination/trivial-dse-calls.ll b/llvm/test/Transforms/DeadStoreElimination/trivial-dse-calls.ll
index 030d315bfd925..8a69f1f55d491 100644
--- a/llvm/test/Transforms/DeadStoreElimination/trivial-dse-calls.ll
+++ b/llvm/test/Transforms/DeadStoreElimination/trivial-dse-calls.ll
@@ -286,3 +286,24 @@ 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
+}
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@llvm/pr-subscribers-llvm-analysis Author: Nikita Popov (nikic) ChangesMemoryLocation::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 #144300. Full diff: https://github.com/llvm/llvm-project/pull/144343.diff 2 Files Affected:
diff --git a/llvm/lib/Analysis/MemoryLocation.cpp b/llvm/lib/Analysis/MemoryLocation.cpp
index 3b42bb412b9ba..c8daab7abde18 100644
--- a/llvm/lib/Analysis/MemoryLocation.cpp
+++ b/llvm/lib/Analysis/MemoryLocation.cpp
@@ -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())
diff --git a/llvm/test/Transforms/DeadStoreElimination/trivial-dse-calls.ll b/llvm/test/Transforms/DeadStoreElimination/trivial-dse-calls.ll
index 030d315bfd925..8a69f1f55d491 100644
--- a/llvm/test/Transforms/DeadStoreElimination/trivial-dse-calls.ll
+++ b/llvm/test/Transforms/DeadStoreElimination/trivial-dse-calls.ll
@@ -286,3 +286,24 @@ 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
+}
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This was referenced Jun 16, 2025
ajaden-codes
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to Jaddyen/llvm-project
that referenced
this pull request
Jun 17, 2025
…ForDest() (llvm#144343) 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 llvm#144300. Proof: https://alive2.llvm.org/ce/z/LKq_dc
fschlimb
pushed a commit
to fschlimb/llvm-project
that referenced
this pull request
Jun 18, 2025
…ForDest() (llvm#144343) 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 llvm#144300. Proof: https://alive2.llvm.org/ce/z/LKq_dc
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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 #144300.
Proof: https://alive2.llvm.org/ce/z/LKq_dc