Skip to content

[VectorCombine] scalarizeLoadExtract - don't create scalar loads if any extract is waiting to be erased #129375

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
merged 3 commits into from
Mar 1, 2025
Merged

[VectorCombine] scalarizeLoadExtract - don't create scalar loads if any extract is waiting to be erased #129375

Show file tree
Hide file tree
Changes from 1 commit
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
93eacbc
[VectorCombine] scalarizeLoadExtract - don't create scalar loads is a…
RKSimon Mar 1, 2025
ba9ba19
fix typo in test case name
RKSimon Mar 1, 2025
52a6511
Just use use_empty as we're only handling ExtractElementInst - isInst…
RKSimon Mar 1, 2025
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
5 changes: 5 additions & 0 deletions llvm/lib/Transforms/Vectorize/VectorCombine.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1579,6 +1579,11 @@ bool VectorCombine::scalarizeLoadExtract(Instruction &I) {
if (!UI || UI->getParent() != LI->getParent())
return false;

// If any extract is waiting to be erased, then bail out as this will
// distort the cost calculation and possibly lead to infinite loops.
if (isInstructionTriviallyDead(UI))
return false;

// Check if any instruction between the load and the extract may modify
// memory.
if (LastCheckedInst->comesBefore(UI)) {
Expand Down
12 changes: 12 additions & 0 deletions llvm/test/Transforms/VectorCombine/X86/load-extractelement-scalarization.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -24,3 +24,15 @@ define void @multiple_extract(ptr %p) {
store i32 %e1, ptr %p1, align 4
ret void
}

; infinite loop if we fold an extract that is waiting to be erased
define void @unsued_extract(ptr %p) {
; CHECK-LABEL: @unsued_extract(
; CHECK-NEXT: ret void
;
%load = load <4 x float>, ptr %p, align 8
%shuffle0 = shufflevector <4 x float> zeroinitializer, <4 x float> %load, <4 x i32> <i32 0, i32 4, i32 1, i32 5>
%shuffle1 = shufflevector <4 x float> %shuffle0, <4 x float> zeroinitializer, <4 x i32> <i32 0, i32 4, i32 poison, i32 poison>
%extract = extractelement <4 x float> %load, i64 1
ret void
}