[all-commits] [llvm/llvm-project] 5dc339: [AArch64][GlobalISel] Fold 64-bit cmps with 64-bit...

[Jessica Paquette via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 5dc339d9825f1dbe788cfb69c88210a59bbf8e3a
      https://github.com/llvm/llvm-project/commit/5dc339d9825f1dbe788cfb69c88210a59bbf8e3a
  Author: Jessica Paquette <jpaquette at apple.com>
  Date:   2021-10-21 (Thu, 21 Oct 2021)

  Changed paths:
    M llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
    M llvm/test/CodeGen/AArch64/GlobalISel/select-cmp.mir

  Log Message:
  -----------
  [AArch64][GlobalISel] Fold 64-bit cmps with 64-bit adds

G_ICMP is selected to an arithmetic overflow op (ADDS/SUBS/etc) with a dead
destination + a CSINC instruction.

We have a fold which allows us to combine 32-bit adds with G_ICMP.

The problem with G_ICMP is that we model it as always having a 32-bit
destination even though it can be a 64-bit operation. So, we were missing some
opportunities for 64-bit folds.

This patch teaches the fold to recognize 64-bit G_ICMPs + refactors some of
the code surrounding CSINC accordingly.

(Later down the line, I think we should probably change the way we handle G_ICMP
in general.)

Differential Revision: https://reviews.llvm.org/D111088