[PATCH] D88429: [InstCombine] visitTrunc - trunc (*shr (trunc A), C) --> trunc(*shr A, C)

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

Please can you post the alive proof you're basing this on?
I don't understand how you arrived at that precondition,
i think it should be much simpler: https://rise4fun.com/Alive/zpJn



================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp:859
+    unsigned AWidth = AType->getScalarSizeInBits();
+    unsigned MaxShiftAmt = std::min<unsigned>(DestWidth, AWidth - DestWidth);
+
----------------
I do not understand why this isn't just `unsigned MaxShiftAmt = AWidth - DestWidth;`


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D88429/new/

https://reviews.llvm.org/D88429