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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
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@ -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);
}
}