[FunctionAttrs][IR] Fix memory attr inference for volatile mem intrinsics (#122926)
Per LangRef volatile operations can read and write inaccessible memory:
> any volatile operation can read and/or modify state which is not
> accessible via a regular load or store in this module
Model this by adding inaccessible memory effects in getMemoryEffects()
if the operation is volatile.
In the future, we should model volatile using operand bundles instead.
Fixes https://github.com/llvm/llvm-project/issues/120932.
diff --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
index 31611df..86a2edb 100644
--- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -839,6 +839,10 @@
FuncME |= MemoryEffects::readOnly();
if (Call->hasClobberingOperandBundles())
FuncME |= MemoryEffects::writeOnly();
+ if (Call->isVolatile()) {
+ // Volatile operations also access inaccessible memory.
+ FuncME |= MemoryEffects::inaccessibleMemOnly();
+ }
Min &= FuncME;
}
diff --git a/llvm/lib/IR/Instructions.cpp b/llvm/lib/IR/Instructions.cpp
index 2d89ec1..8d9b545 100644
--- a/llvm/lib/IR/Instructions.cpp
+++ b/llvm/lib/IR/Instructions.cpp
@@ -643,6 +643,10 @@
if (hasClobberingOperandBundles())
FnME |= MemoryEffects::writeOnly();
}
+ if (isVolatile()) {
+ // Volatile operations also access inaccessible memory.
+ FnME |= MemoryEffects::inaccessibleMemOnly();
+ }
ME &= FnME;
}
return ME;
diff --git a/llvm/test/Transforms/FunctionAttrs/initializes.ll b/llvm/test/Transforms/FunctionAttrs/initializes.ll
index 937595b..5800bc1 100644
--- a/llvm/test/Transforms/FunctionAttrs/initializes.ll
+++ b/llvm/test/Transforms/FunctionAttrs/initializes.ll
@@ -443,7 +443,7 @@
}
define void @memset_volatile(ptr %p) {
-; CHECK: Function Attrs: mustprogress nofree norecurse nounwind willreturn memory(argmem: write)
+; CHECK: Function Attrs: mustprogress nofree norecurse nounwind willreturn memory(argmem: write, inaccessiblemem: readwrite)
; CHECK-LABEL: define void @memset_volatile(
; CHECK-SAME: ptr writeonly [[P:%.*]]) #[[ATTR5:[0-9]+]] {
; CHECK-NEXT: call void @llvm.memset.p0.i64(ptr [[P]], i8 2, i64 9, i1 true)
@@ -478,7 +478,7 @@
}
define void @memcpy_volatile(ptr %p, ptr %p2) {
-; CHECK: Function Attrs: mustprogress nofree norecurse nounwind willreturn memory(argmem: readwrite)
+; CHECK: Function Attrs: mustprogress nofree norecurse nounwind willreturn memory(argmem: readwrite, inaccessiblemem: readwrite)
; CHECK-LABEL: define void @memcpy_volatile(
; CHECK-SAME: ptr writeonly [[P:%.*]], ptr readonly [[P2:%.*]]) #[[ATTR6:[0-9]+]] {
; CHECK-NEXT: call void @llvm.memcpy.p0.p0.i64(ptr [[P]], ptr [[P2]], i64 9, i1 true)
@@ -541,7 +541,7 @@
}
define void @memmove_volatile(ptr %p, ptr %p2) {
-; CHECK: Function Attrs: mustprogress nofree norecurse nounwind willreturn memory(argmem: readwrite)
+; CHECK: Function Attrs: mustprogress nofree norecurse nounwind willreturn memory(argmem: readwrite, inaccessiblemem: readwrite)
; CHECK-LABEL: define void @memmove_volatile(
; CHECK-SAME: ptr writeonly [[P:%.*]], ptr readonly [[P2:%.*]]) #[[ATTR6]] {
; CHECK-NEXT: call void @llvm.memmove.p0.p0.i64(ptr [[P]], ptr [[P2]], i64 9, i1 true)
diff --git a/llvm/test/Transforms/FunctionAttrs/nosync.ll b/llvm/test/Transforms/FunctionAttrs/nosync.ll
index de5398f..9abfbb2 100644
--- a/llvm/test/Transforms/FunctionAttrs/nosync.ll
+++ b/llvm/test/Transforms/FunctionAttrs/nosync.ll
@@ -236,7 +236,7 @@
; negative, checking volatile intrinsics.
define i32 @memcpy_volatile(ptr %ptr1, ptr %ptr2) {
-; CHECK: Function Attrs: mustprogress nofree norecurse nounwind willreturn memory(argmem: readwrite)
+; CHECK: Function Attrs: mustprogress nofree norecurse nounwind willreturn memory(argmem: readwrite, inaccessiblemem: readwrite)
; CHECK-LABEL: @memcpy_volatile(
; CHECK-NEXT: call void @llvm.memcpy.p0.p0.i32(ptr [[PTR1:%.*]], ptr [[PTR2:%.*]], i32 8, i1 true)
; CHECK-NEXT: ret i32 4
