[PATCH] D92745: [LoopIdiomRecognize] Teach detectShiftUntilZeroIdiom to recognize loops where the counter is decrementing.
Craig Topper via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Mon Dec 7 00:58:39 PST 2020
craig.topper added inline comments.
================
Comment at: llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp:1484-1489
for (BasicBlock::iterator Iter = LoopEntry->getFirstNonPHI()->getIterator(),
IterE = LoopEntry->end();
Iter != IterE; Iter++) {
Instruction *Inst = &*Iter;
if (Inst->getOpcode() != Instruction::Add)
continue;
----------------
lebedev.ri wrote:
> Preexisting problem, but this is //kinda// broken.
> If we have a second `add` in the loop,
> and it happens to be before the one we are looking for,
> we'll fail to detect the idiom.
> The detection should not involve linear scan over instructions.
All the fails are continues. So wouldn’t the second add also have to be a recurrence with 1/-1?
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D92745/new/
https://reviews.llvm.org/D92745
More information about the llvm-commits
mailing list