[all-commits] [llvm/llvm-project] bfd512: [InstCombine] improve analysis of FP->int->FP to e...

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  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: bfd512160fe091bdd45199e5db884a24cd9d5f59
      https://github.com/llvm/llvm-project/commit/bfd512160fe091bdd45199e5db884a24cd9d5f59
  Author: Sanjay Patel <spatel at rotateright.com>
  Date:   2020-05-17 (Sun, 17 May 2020)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
    M llvm/test/Transforms/InstCombine/fpextend.ll

  Log Message:
  -----------
  [InstCombine] improve analysis of FP->int->FP to eliminate fpextend

This was originally in D79116.
Converting from a narrow-enough FP source value to integer and
back to FP guarantees that the conversion to FP is exact because
of UB/poison-on-overflow.

This was suggested in PR36617:
https://bugs.llvm.org/show_bug.cgi?id=36617#c19