[all-commits] [llvm/llvm-project] 262f2f: [IndVars] Use symbolic max block exit count to han...

[Max Kazantsev via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 262f2fed65b83ba9b64227b983d5ed95883fd71e
      https://github.com/llvm/llvm-project/commit/262f2fed65b83ba9b64227b983d5ed95883fd71e
  Author: Max Kazantsev <mkazantsev at azul.com>
  Date:   2022-12-09 (Fri, 09 Dec 2022)

  Changed paths:
    M llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
    M llvm/test/Transforms/IndVarSimplify/turn-to-invariant.ll

  Log Message:
  -----------
  [IndVars] Use symbolic max block exit count to handle the last iter

Old logic: when loop symbolic max exit count matched *exact* block exit count,
assume that all subsequent blocks will do 1 iteration less.

New logic: when loop symbolic max exit count matched *symbolic max* block exit count,
assume that all subsequent blocks will do 1 iteration less.

The new logic is still legal and is more permissive in situations when exact
block exit count is not known.

Differential Revision: https://reviews.llvm.org/D139692
Reviewed By: nikic