[PATCH] D99481: [InstCombine] Fix miscompile on GEP+load to icmp fold (PR45210)

[Eli Friedman via Phabricator via llvm-commits]

efriedma added inline comments.


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp:293
+    if (countTrailingZeros(ElementSize) != 0) {
+      Value *Mask = ConstantInt::get(Idx->getType(), -1);
+      Mask = Builder.CreateLShr(Mask, countTrailingZeros(ElementSize));
----------------
Using "-1" like this won't sign-extend correctly if anyone ever uses a pointer type wider than 64 bits.

There are a few ways to solve this; you can use ConstantInt::getSigned(), or APInt::getLowBitsSet().


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D99481/new/

https://reviews.llvm.org/D99481