Skip to content

[DSE] Fixes bug caused by skipped read clobbers #83181

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

Closed
wants to merge 1 commit into from
Closed

[DSE] Fixes bug caused by skipped read clobbers #83181

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
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
3 changes: 2 additions & 1 deletion llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1274,7 +1274,8 @@ struct DSEState {
if (CB->onlyAccessesInaccessibleMemory())
return false;

return isRefSet(BatchAA.getModRefInfo(UseInst, DefLoc));
AAQueryInfo TmpAAQI(AA, &EI);
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This shouldn't be necessary. AA.getModRefInfo(UseInst, DefLoc) should work.

Copy link
Contributor Author

@vporpo vporpo Feb 27, 2024 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

No, that won't work because it won't use EarliestEscapeInfo and the result will be different.

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Is there a better way to call getModeRefInfo() and using EI for the query, without having to use the temporary AAQueryInfo ?

return isRefSet(AA.getModRefInfo(UseInst, DefLoc, TmpAAQI));
}

/// Returns true if a dependency between \p Current and \p KillingDef is
Expand Down
41 changes: 41 additions & 0 deletions llvm/test/Transforms/DeadStoreElimination/read-clobber-skipped.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,41 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
; RUN: opt -S -passes=dse < %s | FileCheck %s
;
; DSE kills both `store i32 44, ptr %struct.byte.4, align 4` and
; `call void @llvm.memset.p0.i64(...)` but the memset should not be killed
; because it has a clobber read: `%ret = load ptr, ptr %struct.byte.8`

%struct.type = type { ptr, ptr }

define ptr @foo(ptr noundef %ptr) {
; CHECK-LABEL: define ptr @foo(
; CHECK-SAME: ptr noundef [[PTR:%.*]]) {
; CHECK-NEXT: [[STRUCT_ALLOCA:%.*]] = alloca [[STRUCT_TYPE:%.*]], align 8
; CHECK-NEXT: call void @llvm.lifetime.start.p0(i64 56, ptr nonnull [[STRUCT_ALLOCA]]) #[[ATTR2:[0-9]+]]
; CHECK-NEXT: [[STRUCT_BYTE_8:%.*]] = getelementptr inbounds i8, ptr [[STRUCT_ALLOCA]], i64 8
; CHECK-NEXT: [[TMP1:%.*]] = getelementptr inbounds i8, ptr [[STRUCT_BYTE_8]], i64 4
; CHECK-NEXT: call void @llvm.memset.p0.i64(ptr noundef nonnull align 4 [[TMP1]], i8 42, i64 4, i1 false)
; CHECK-NEXT: store i32 43, ptr [[STRUCT_BYTE_8]], align 4
; CHECK-NEXT: [[RET:%.*]] = load ptr, ptr [[STRUCT_BYTE_8]], align 8
; CHECK-NEXT: call void @llvm.lifetime.end.p0(i64 56, ptr nonnull [[STRUCT_ALLOCA]]) #[[ATTR2]]
; CHECK-NEXT: ret ptr [[RET]]
;
%struct.alloca = alloca %struct.type, align 8
call void @llvm.lifetime.start.p0(i64 56, ptr nonnull %struct.alloca) nounwind
%struct.byte.8 = getelementptr inbounds i8, ptr %struct.alloca, i64 8
; Set %struct.alloca[8, 16) to 42.
call void @llvm.memset.p0.i64(ptr noundef nonnull align 4 %struct.byte.8, i8 42, i64 8, i1 false)
; Set %struct.alloca[8, 12) to 43.
store i32 43, ptr %struct.byte.8, align 4
; Set %struct.alloca[4, 8) to 44.
%struct.byte.4 = getelementptr inbounds i8, ptr %struct.alloca, i64 4
store i32 44, ptr %struct.byte.4, align 4
; Return %struct.alloca[8, 16).
%ret = load ptr, ptr %struct.byte.8
call void @llvm.lifetime.end.p0(i64 56, ptr nonnull %struct.alloca) nounwind
ret ptr %ret
}

declare void @llvm.memset.p0.i64(ptr nocapture writeonly, i8, i64, i1 immarg) #0
declare void @llvm.lifetime.end.p0(i64 immarg, ptr nocapture) #2
declare void @llvm.lifetime.start.p0(i64 immarg, ptr nocapture) #2