[all-commits] [llvm/llvm-project] 0a07ae: [KnownBits] Add support for X*X self-multiplication

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 0a07ae6ebfffb77243787f941d02f281a0041762
      https://github.com/llvm/llvm-project/commit/0a07ae6ebfffb77243787f941d02f281a0041762
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2021-09-07 (Tue, 07 Sep 2021)

  Changed paths:
    M llvm/include/llvm/Support/KnownBits.h
    M llvm/lib/Support/KnownBits.cpp
    M llvm/unittests/Support/KnownBitsTest.cpp

  Log Message:
  -----------
  [KnownBits] Add support for X*X self-multiplication

Add KnownBits handling and unit tests for X*X self-multiplication cases which guarantee that bit1 of their results will be zero - see PR48683.

https://alive2.llvm.org/ce/z/NN_eaR

The next step will be to add suitable test coverage so this can be enabled in ValueTracking/DAG/GlobalISel - currently only a single Analysis/ScalarEvolution test is affected.

Differential Revision: https://reviews.llvm.org/D108992