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Revert "Revert r253253 and r253126: "Don't recompute LCSSA after loop-unrolling when possible.""

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The bug in IndVarSimplify was fixed in r254976, r254977, so I'm
reapplying the original patch for avoiding redundant LCSSA recomputation.

This reverts commit ffe3b434e505e403146aff00be0c177bb6d13466.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@255133 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Michael Zolotukhin 2015-12-09 18:20:28 +00:00
parent 65711ad4e3
commit 4c0fb60923
1 changed files with 12 additions and 2 deletions
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14
lib/Transforms/Utils/LoopUnroll.cpp
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@ -221,6 +221,12 @@ bool llvm::UnrollLoop(Loop *L, unsigned Count, unsigned TripCount,
// Are we eliminating the loop control altogether?
bool CompletelyUnroll = Count == TripCount;
SmallVector<BasicBlock *, 4> ExitBlocks;
L->getExitBlocks(ExitBlocks);
Loop *ParentL = L->getParentLoop();
bool AllExitsAreInsideParentLoop = !ParentL ||
std::all_of(ExitBlocks.begin(), ExitBlocks.end(),
[&](BasicBlock *BB) { return ParentL->contains(BB); });
// We assume a run-time trip count if the compiler cannot
// figure out the loop trip count and the unroll-runtime
@ -544,7 +550,7 @@ bool llvm::UnrollLoop(Loop *L, unsigned Count, unsigned TripCount,
if (!OuterL && !CompletelyUnroll)
OuterL = L;
if (OuterL) {
simplifyLoop(OuterL, DT, LI, PP, SE, AC);
bool Simplified = simplifyLoop(OuterL, DT, LI, PP, SE, AC);
// 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
@ -554,7 +560,11 @@ bool llvm::UnrollLoop(Loop *L, unsigned Count, unsigned TripCount,
while (OuterL->getParentLoop() != LatchLoop)
OuterL = OuterL->getParentLoop();
formLCSSARecursively(*OuterL, *DT, LI, SE);
if (CompletelyUnroll && (!AllExitsAreInsideParentLoop || Simplified))
formLCSSARecursively(*OuterL, *DT, LI, SE);
else
assert(OuterL->isLCSSAForm(*DT) &&
"Loops should be in LCSSA form after loop-unroll.");
}
}