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LoopRotate: Don't rotate single BB loops

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Swift SVN r21123
This commit is contained in:
Arnold Schwaighofer
2014-08-09 00:05:29 +00:00
parent e3b33d7bca
commit e5e11b9ade
1 changed files with 24 additions and 18 deletions
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42
lib/SILPasses/LoopRotate.cpp
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@@ -229,7 +229,8 @@ static bool rotateLoopAtMostUpToLatch(SILLoop *L, DominanceInfo *DT,
if (!ShouldRotate)
return false;
bool DidRotate = rotateLoop(L, DT, LI, true, Latch, ShouldVerify);
bool DidRotate = rotateLoop(L, DT, LI, false /* RotateSingleBlockLoops */,
Latch, ShouldVerify);
// Keep rotating at most until we hit the original latch.
if (DidRotate)
@@ -256,25 +257,12 @@ bool swift::rotateLoop(SILLoop *L, DominanceInfo *DT, SILLoopInfo *LI,
assert(L != nullptr && DT != nullptr && LI != nullptr &&
"Missing loop information");
SILBasicBlock *Header = L->getHeader();
if (!Header || (!RotateSingleBlockLoops && Header == UpTo))
auto *Header = L->getHeader();
if (!Header)
return false;
assert(RotateSingleBlockLoops || L->getBlocks().size() != 1);
// Need a conditional branch that guards the entry into the loop.
auto *LoopEntryBranch = dyn_cast<CondBranchInst>(Header->getTerminator());
if (!LoopEntryBranch)
return false;
// The header needs to exit the loop.
if (!L->isLoopExiting(Header)) {
DEBUG(llvm::dbgs() << *L << " not a exiting header\n");
DEBUG(L->getHeader()->getParent()->dump());
return false;
}
// We need a preheader.
// We need a preheader - this is also a cannonicalization for follow-up
// passes.
auto *Preheader = L->getLoopPreheader();
bool ChangedCFG = false;
if (!Preheader) {
@@ -293,6 +281,24 @@ bool swift::rotateLoop(SILLoop *L, DominanceInfo *DT, SILLoopInfo *LI,
}
}
if (!RotateSingleBlockLoops && Header == UpTo)
return ChangedCFG;
assert(RotateSingleBlockLoops || L->getBlocks().size() != 1);
// Need a conditional branch that guards the entry into the loop.
auto *LoopEntryBranch = dyn_cast<CondBranchInst>(Header->getTerminator());
if (!LoopEntryBranch)
return ChangedCFG;
// The header needs to exit the loop.
if (!L->isLoopExiting(Header)) {
DEBUG(llvm::dbgs() << *L << " not a exiting header\n");
DEBUG(L->getHeader()->getParent()->dump());
return ChangedCFG;
}
// We need a single backedge and the latch must not exit the loop if it is
// also the header.
auto *Latch = L->getLoopLatch();