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

The change exposed a bug in IndVarSimplify (PR25578), which led to a
failure (PR25538). When the bug is fixed, this patch can be reapplied.

The tests are kept in tree, as they're useful anyway, and will not break
with this revert.

llvm-svn: 253596
This commit is contained in:
Michael Zolotukhin 2015-11-19 20:28:32 +00:00
parent b85fc5c799
commit 6c11c04db3
1 changed files with 2 additions and 12 deletions
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14
llvm/lib/Transforms/Utils/LoopUnroll.cpp
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@ -221,12 +221,6 @@ 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
@ -550,7 +544,7 @@ bool llvm::UnrollLoop(Loop *L, unsigned Count, unsigned TripCount,
if (!OuterL && !CompletelyUnroll)
OuterL = L;
if (OuterL) {
bool Simplified = simplifyLoop(OuterL, DT, LI, PP, SE, AC);
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
@ -560,11 +554,7 @@ bool llvm::UnrollLoop(Loop *L, unsigned Count, unsigned TripCount,
while (OuterL->getParentLoop() != LatchLoop)
OuterL = OuterL->getParentLoop();
if (CompletelyUnroll && (!AllExitsAreInsideParentLoop || Simplified))
formLCSSARecursively(*OuterL, *DT, LI, SE);
else
assert(OuterL->isLCSSAForm(*DT) &&
"Loops should be in LCSSA form after loop-unroll.");
formLCSSARecursively(*OuterL, *DT, LI, SE);
}
}