[all-commits] [llvm/llvm-project] 20b1a1: [ARM] Mark <= -1 immediate constant as cheap

[David Green via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 20b1a16a696ace537103a92d2f4fd09a137e9406
      https://github.com/llvm/llvm-project/commit/20b1a16a696ace537103a92d2f4fd09a137e9406
  Author: David Green <david.green at arm.com>
  Date:   2021-10-03 (Sun, 03 Oct 2021)

  Changed paths:
    M llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
    M llvm/test/CodeGen/ARM/consthoist-icmpimm.ll

  Log Message:
  -----------
  [ARM] Mark <= -1 immediate constant as cheap

A <= -1 constant on a compare can be converted to a < 0 operation, which
is usually cheap. If we mark the constant as cheap, preventing hoisting,
we allow that fold to happen even across different blocks.

Differential Revision: https://reviews.llvm.org/D109360