[all-commits] [llvm/llvm-project] 3122c6: [AArch64][SVE] Remove chains of unnecessary SVE re...

[Joe Ellis via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 3122c66aee7b709046753873c4e94db73742b3de
      https://github.com/llvm/llvm-project/commit/3122c66aee7b709046753873c4e94db73742b3de
  Author: Joe Ellis <joe.ellis at arm.com>
  Date:   2021-01-13 (Wed, 13 Jan 2021)

  Changed paths:
    M llvm/lib/Target/AArch64/SVEIntrinsicOpts.cpp
    M llvm/test/CodeGen/AArch64/sve-intrinsic-opts-reinterpret.ll

  Log Message:
  -----------
  [AArch64][SVE] Remove chains of unnecessary SVE reinterpret intrinsics

This commit extends SVEIntrinsicOpts::optimizeConvertFromSVBool to
identify and remove longer chains of redundant SVE reintepret
intrinsics. For example, the following chain of redundant SVE
reinterprets is now recognised as redundant:

    %a = <vscale x 2 x i1>
    %1 = <vscale x 16 x i1> @llvm.aarch64.sve.convert.to.svbool(<vscale x 2 x i1> %a)
    %2 = <vscale x 4 x i1> @llvm.aarch64.sve.convert.from.svbool(<vscale x 16 x i1> %1)
    %3 = <vscale x 16 x i1> @llvm.aarch64.sve.convert.to.svbool(<vscale x 4 x i1> %2)
    %4 = <vscale x 4 x i1> @llvm.aarch64.sve.convert.from.svbool(<vscale x 16 x i1> %3)
    %5 = <vscale x 16 x i1> @llvm.aarch64.sve.convert.to.svbool(<vscale x 4 x i1> %4)
    %6 = <vscale x 2 x i1> @llvm.aarch64.sve.convert.from.svbool(<vscale x 16 x i1> %5)
    ret <vscale x 2 x i1> %6

and will be replaced with:

    ret <vscale x 2 x i1> %a

Eliminating these can sometimes mean emitting fewer unnecessary
loads/stores when lowering to assembly.

Differential Revision: https://reviews.llvm.org/D94074