[PATCH] D92745: [LoopIdiomRecognize] Teach detectShiftUntilZeroIdiom to recognize loops where the counter is decrementing.

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added inline comments.


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Comment at: llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp:1756-1766
+  if (cast<ConstantInt>(CntInst->getOperand(1))->isOne()) {
+    // If the counter was being incremented in the loop, add NewCount to the
+    // counter's initial value, but only if the initial value is not zero.
+    ConstantInt *InitConst = dyn_cast<ConstantInt>(CntInitVal);
+    if (!InitConst || !InitConst->isZero())
+      NewCount = Builder.CreateAdd(NewCount, CntInitVal);
+  } else {
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I think this might be marginally less awkward to write this as:


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D92745/new/

https://reviews.llvm.org/D92745