Skip to content

[IR] Handle nofree noalias in canBeFreed() #200194

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
nikic merged 2 commits into from
Jun 1, 2026
Merged

[IR] Handle nofree noalias in canBeFreed() #200194

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
f0a23fd
[IR] Handle nofree noalias in canBeFreed()
nikic May 28, 2026
c53024e
Drop nosync attribute
nikic May 28, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
6 changes: 6 additions & 0 deletions llvm/lib/IR/Value.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -842,6 +842,12 @@ bool Value::canBeFreed() const {
const Function *F = A->getParent();
if (F->doesNotFreeMemory() && F->hasNoSync())
return false;

// nofree on the argument ensures that it cannot be freed through that
// pointer. noalias additionally ensures that it can't be freed through
// another pointer to the same allocation. Readonly implies nofree.
if ((A->hasNoFreeAttr() || A->onlyReadsMemory()) && A->hasNoAliasAttr())
return false;
}

if (auto *ITP = dyn_cast<IntToPtrInst>(this);
Expand Down
23 changes: 18 additions & 5 deletions llvm/test/Analysis/ValueTracking/memory-dereferenceable.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -265,25 +265,38 @@ define void @infer_func_attrs2(ptr dereferenceable(8) %p) readonly {
}

; CHECK-LABEL: 'infer_noalias1'
; GLOBAL: %p
; POINT-NOT: %p
; FIXME: Can be inferred from attributes
; CHECK: %p
define void @infer_noalias1(ptr dereferenceable(8) noalias nofree %p) {
call void @mayfree()
%v = load i32, ptr %p
ret void
}

; CHECK-LABEL: 'infer_noalias2'
; CHECK: %p
define void @infer_noalias2(ptr dereferenceable(8) noalias readonly %p) {
call void @mayfree()
%v = load i32, ptr %p
ret void
}

; CHECK-LABEL: 'infer_missing_noalias1'
; GLOBAL: %p
; POINT-NOT: %p
; FIXME: Can be inferred from attributes
define void @infer_noalias2(ptr dereferenceable(8) noalias readonly %p) nosync {
define void @infer_missing_noalias1(ptr dereferenceable(8) nofree %p) {
call void @mayfree()
%v = load i32, ptr %p
ret void
}

; CHECK-LABEL: 'infer_missing_noalias2'
; GLOBAL: %p
; POINT-NOT: %p
define void @infer_missing_noalias2(ptr dereferenceable(8) readonly %p) {
call void @mayfree()
%v = load i32, ptr %p
ret void
}

; Just check that we don't crash.
; CHECK-LABEL: 'opaque_type_crasher'
Expand Down