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Preserve loop metadata when folding branches to a common destination.

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Differential Revision: https://reviews.llvm.org/D27830


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@289992 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Michael Kuperstein 2016-12-16 21:23:59 +00:00
parent 4d9c93dc3f
commit 569cd219c7
2 changed files with 33 additions and 0 deletions
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5
lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -2792,6 +2792,11 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI, unsigned BonusInstThreshold) {
PBI = New_PBI;
}
// If BI was a loop latch, it may have had associated loop metadata.
// We need to copy it to the new latch, that is, PBI.
if (MDNode *LoopMD = BI->getMetadata(LLVMContext::MD_loop))
PBI->setMetadata(LLVMContext::MD_loop, LoopMD);
// TODO: If BB is reachable from all paths through PredBlock, then we
// could replace PBI's branch probabilities with BI's.

28
test/Transforms/LoopSimplify/preserve-llvm-loop-metadata.ll
View File

@ -1,5 +1,6 @@
; RUN: opt -loop-simplify -S < %s | FileCheck %s
; CHECK-LABEL: @test1
define void @test1(i32 %n) {
entry:
br label %while.cond
@ -35,6 +36,33 @@ while.end: ; preds = %while.cond
; CHECK: if.else
; CHECK-NOT: br {{.*}}!llvm.loop{{.*}}
; CHECK-LABEL: @test2
; CHECK: for.body:
; CHECK: br i1 %{{.*}}, label %for.body, label %cleanup.loopexit, !llvm.loop !0
define void @test2(i32 %k) {
entry:
%cmp9 = icmp sgt i32 %k, 0
br i1 %cmp9, label %for.body.preheader, label %cleanup
for.body.preheader: ; preds = %entry
br label %for.body
for.cond: ; preds = %for.body
%cmp = icmp slt i32 %inc, %k
br i1 %cmp, label %for.body, label %cleanup.loopexit, !llvm.loop !0
for.body: ; preds = %for.body.preheader, %for.cond
%i.010 = phi i32 [ %inc, %for.cond ], [ 0, %for.body.preheader ]
%cmp3 = icmp sgt i32 %i.010, 3
%inc = add nsw i32 %i.010, 1
br i1 %cmp3, label %cleanup.loopexit, label %for.cond
cleanup.loopexit: ; preds = %for.body, %for.cond
br label %cleanup
cleanup: ; preds = %cleanup.loopexit, %entry
ret void
}
!0 = distinct !{!0, !1}
!1 = !{!"llvm.loop.distribute.enable", i1 true}