[all-commits] [llvm/llvm-project] 32c999: [InstCombine] Fix errno bug in pow expansion to sqrt

[Hubert Tong via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 32c9991dab5cb1454959561c77f9d0089d981429
      https://github.com/llvm/llvm-project/commit/32c9991dab5cb1454959561c77f9d0089d981429
  Author: Hubert Tong <hubert.reinterpretcast at gmail.com>
  Date:   2020-09-22 (Tue, 22 Sep 2020)

  Changed paths:
    M llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
    M llvm/test/Transforms/InstCombine/pow-1.ll
    M llvm/test/Transforms/InstCombine/pow-sqrt.ll
    M llvm/test/Transforms/InstCombine/win-math.ll

  Log Message:
  -----------
  [InstCombine] Fix errno bug in pow expansion to sqrt

A conversion from `pow` to `sqrt` shall not call an `errno`-setting
`sqrt` with -//infinity//: the `sqrt` will set `EDOM` where the `pow`
call need not.

This patch avoids the erroneous (pun not intended) transformation by
applying the restrictions discussed in the thread for
https://lists.llvm.org/pipermail/llvm-dev/2020-September/145051.html.

The existing tests are updated (depending on emphasis in the checks for
library calls, avoidance of overlap, and overall coverage):
  - to add `ninf`, retaining the intended library call,
  - to use the intrinsic, retaining the use of `select`, or
  - to expect the replacement to not occur.

The following is tested:
  - The pow intrinsic folds to a `select` instruction to
    handle -//infinity//.
  - The pow library call folds, with `ninf`, to `sqrt` without the
    `select` instruction associated with handling -//infinity//.
  - The pow library call does not fold to `sqrt` without `ninf`.

Reviewed By: spatel

Differential Revision: https://reviews.llvm.org/D87877


  Commit: a60852e9d692e3c38d9b58b7ec1679e07af2b8f7
      https://github.com/llvm/llvm-project/commit/a60852e9d692e3c38d9b58b7ec1679e07af2b8f7
  Author: Hubert Tong <hubert.reinterpretcast at gmail.com>
  Date:   2020-09-22 (Tue, 22 Sep 2020)

  Changed paths:
    M llvm/test/Transforms/InstCombine/pow-sqrt.ll

  Log Message:
  -----------
  [InstCombine][NFC][tests] Add ninf base value case to pow-sqrt.ll


Compare: https://github.com/llvm/llvm-project/compare/d6ac649ccda2...a60852e9d692