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LCSSA should be performed on the outermost affected loop while unrolling loop.

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During loop-unroll, loop exits from the current loop may end up in in different
outer loop. This requires to re-form LCSSA recursively for one level down from
the outer most loop where loop exits are landed during unroll. This fixes PR18861.

Differential Revision: http://reviews.llvm.org/D2976



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209796 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dinesh Dwivedi 2014-05-29 06:47:23 +00:00
parent ed0e90576d
commit 2a747bf1c5
2 changed files with 52 additions and 0 deletions
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9
lib/Transforms/Utils/LoopUnroll.cpp
View File

@ -487,6 +487,15 @@ bool llvm::UnrollLoop(Loop *L, unsigned Count, unsigned TripCount,
if (OuterL) {
ScalarEvolution *SE = PP->getAnalysisIfAvailable<ScalarEvolution>();
simplifyLoop(OuterL, DT, LI, PP, /*AliasAnalysis*/ nullptr, SE);
// LCSSA must be performed on the outermost affected loop. The unrolled
// loop's last loop latch is guaranteed to be in the outermost loop after
// deleteLoopFromQueue updates LoopInfo.
Loop *LatchLoop = LI->getLoopFor(Latches.back());
if (!OuterL->contains(LatchLoop))
while (OuterL->getParentLoop() != LatchLoop)
OuterL = OuterL->getParentLoop();
formLCSSARecursively(*OuterL, *DT, SE);
}
}

43
test/Transforms/LoopUnroll/pr18861.ll Normal file
View File

@ -0,0 +1,43 @@
; RUN: opt < %s -loop-unroll -indvars -disable-output
@b = external global i32, align 4
; Function Attrs: nounwind uwtable
define void @fn1() #0 {
entry:
br label %for.cond1thread-pre-split
for.cond1thread-pre-split: ; preds = %for.inc8, %entry
%storemerge1 = phi i32 [ 0, %entry ], [ %inc9, %for.inc8 ]
br i1 undef, label %for.inc8, label %for.cond2.preheader.lr.ph
for.cond2.preheader.lr.ph: ; preds = %for.cond1thread-pre-split
br label %for.cond2.preheader
for.cond2.preheader: ; preds = %for.inc5, %for.cond2.preheader.lr.ph
br label %for.cond2
for.cond2: ; preds = %for.body3, %for.cond2.preheader
%storemerge = phi i32 [ %add, %for.body3 ], [ 0, %for.cond2.preheader ]
%cmp = icmp slt i32 %storemerge, 1
br i1 %cmp, label %for.body3, label %for.inc5
for.body3: ; preds = %for.cond2
%tobool4 = icmp eq i32 %storemerge, 0
%add = add nsw i32 %storemerge, 1
br i1 %tobool4, label %for.cond2, label %if.then
if.then: ; preds = %for.body3
store i32 %storemerge1, i32* @b, align 4
ret void
for.inc5: ; preds = %for.cond2
br i1 undef, label %for.cond1.for.inc8_crit_edge, label %for.cond2.preheader
for.cond1.for.inc8_crit_edge: ; preds = %for.inc5
br label %for.inc8
for.inc8: ; preds = %for.cond1.for.inc8_crit_edge, %for.cond1thread-pre-split
%inc9 = add nsw i32 %storemerge1, 1
br label %for.cond1thread-pre-split
}