[all-commits] [llvm/llvm-project] 5a6dfb: [IndVars] Replace PHIs if loop exits on 1st iteration

[Max Kazantsev via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 5a6dfb27ca7424f15a20f9bb7ec90d858865faa3
      https://github.com/llvm/llvm-project/commit/5a6dfb27ca7424f15a20f9bb7ec90d858865faa3
  Author: Max Kazantsev <mkazantsev at azul.com>
  Date:   2021-09-13 (Mon, 13 Sep 2021)

  Changed paths:
    M llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
    M llvm/test/Transforms/IndVarSimplify/eliminate-backedge.ll
    M llvm/test/Transforms/IndVarSimplify/eliminate-exit-no-dl.ll
    M llvm/test/Transforms/IndVarSimplify/floating-point-iv.ll

  Log Message:
  -----------
  [IndVars] Replace PHIs if loop exits on 1st iteration

This is a part of D108910.
We replace all loop PHIs with values coming from the loop preheader if
we proved that backedge is never taken.

Patch by Dmitry Makogon!

Differential Revision: https://reviews.llvm.org/D109596
Reviewed By: lebedev.ri