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[LoopUtils] Extend the scope of getLoopEstimatedTripCount

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With this patch the getLoopEstimatedTripCount function will
accept also the loops where there are more than one exit but
all exits except latch block should ends up with a call to deopt.

This side exits should not impact the estimated trip count.

Reviewers: reames, mkuper, danielcdh
Reviewed By: reames
Subscribers: fhahn, lebedev.ri, hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D64553

llvm-svn: 366042
This commit is contained in:
Serguei Katkov 2019-07-15 06:42:39 +00:00
parent e179425280
commit cb15cb48f4
1 changed files with 14 additions and 6 deletions
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20
lib/Transforms/Utils/LoopUtils.cpp
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@ -621,20 +621,28 @@ void llvm::deleteDeadLoop(Loop *L, DominatorTree *DT = nullptr,
}
Optional<unsigned> llvm::getLoopEstimatedTripCount(Loop *L) {
// Only support loops with a unique exiting block, and a latch.
if (!L->getExitingBlock())
return None;
// Support loops with an exiting latch and other existing exists only
// deoptimize.
// Get the branch weights for the loop's backedge.
BranchInst *LatchBR =
dyn_cast<BranchInst>(L->getLoopLatch()->getTerminator());
if (!LatchBR || LatchBR->getNumSuccessors() != 2)
BasicBlock *Latch = L->getLoopLatch();
if (!Latch)
return None;
BranchInst *LatchBR = dyn_cast<BranchInst>(Latch->getTerminator());
if (!LatchBR || LatchBR->getNumSuccessors() != 2 || !L->isLoopExiting(Latch))
return None;
assert((LatchBR->getSuccessor(0) == L->getHeader() ||
LatchBR->getSuccessor(1) == L->getHeader()) &&
"At least one edge out of the latch must go to the header");
SmallVector<BasicBlock *, 4> ExitBlocks;
L->getUniqueNonLatchExitBlocks(ExitBlocks);
if (any_of(ExitBlocks, [](const BasicBlock *EB) {
return !EB->getTerminatingDeoptimizeCall();
}))
return None;
// To estimate the number of times the loop body was executed, we want to
// know the number of times the backedge was taken, vs. the number of times
// we exited the loop.