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[BasicBlockUtils] Do not move loop metadata if outer loop header. 

Fixes a bug preventing moving the loop's metadata to an outer loop's header,
which happens if the loop's exit is also the header of an outer loop.

Adjusts test for above.

Fixes #55416.

Differential Revision: https://reviews.llvm.org/D125574
This commit is contained in:
Hendrik Greving 2022-05-13 10:53:13 -07:00
parent e5d8fb690e
commit 4f93d5cc1d
2 changed files with 6 additions and 4 deletions
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6
llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
View File

@ -1162,7 +1162,11 @@ SplitBlockPredecessorsImpl(BasicBlock *BB, ArrayRef<BasicBlock *> Preds,
if (NewLatch != OldLatch) {
MDNode *MD = OldLatch->getTerminator()->getMetadata("llvm.loop");
NewLatch->getTerminator()->setMetadata("llvm.loop", MD);
OldLatch->getTerminator()->setMetadata("llvm.loop", nullptr);
// It's still possible that OldLatch is the latch of another inner loop,
// in which case we do not remove the metadata.
Loop *IL = LI->getLoopFor(OldLatch);
if (IL && IL->getLoopLatch() != OldLatch)
OldLatch->getTerminator()->setMetadata("llvm.loop", nullptr);
}
}

4
llvm/test/Transforms/LoopSimplify/update_latch_md2.ll
View File

@ -1,13 +1,11 @@
; Tests loop-simplify does not move the loop metadata, because
; the loopexit block is not the latch of the loop _bb6.
; FIXME(#55416): The metadata should not move.
; RUN: opt < %s -passes=loop-simplify -S | FileCheck %s
; CHECK-LABEL: loop.header.loopexit:
; CHECK: br label %loop.header, !llvm.loop !0
; CHECK-LABEL: loop.latch:
; CHECK-NOT: br i1 %p, label %loop.latch, label %loop.header.loopexit, !llvm.loop !0
; CHECK: br i1 %p, label %loop.latch, label %loop.header.loopexit, !llvm.loop !0
define void @func(i1 %p) {
entry: