[all-commits] [llvm/llvm-project] 59087d: [X86] combineX86ShufflesConstants - constant fold ...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 59087dce3b588c48dbb102d801dd986ea81eaac9
      https://github.com/llvm/llvm-project/commit/59087dce3b588c48dbb102d801dd986ea81eaac9
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2021-11-12 (Fri, 12 Nov 2021)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/test/CodeGen/X86/combine-concatvectors.ll
    M llvm/test/CodeGen/X86/combine-multiplies.ll
    M llvm/test/CodeGen/X86/combine-pmuldq.ll
    M llvm/test/CodeGen/X86/combine-rotates.ll
    M llvm/test/CodeGen/X86/combine-shl.ll
    M llvm/test/CodeGen/X86/hoist-and-by-const-from-shl-in-eqcmp-zero.ll
    M llvm/test/CodeGen/X86/madd.ll
    M llvm/test/CodeGen/X86/omit-urem-of-power-of-two-or-zero-when-comparing-with-zero.ll
    M llvm/test/CodeGen/X86/sdiv-exact.ll
    M llvm/test/CodeGen/X86/srem-seteq-vec-nonsplat.ll
    M llvm/test/CodeGen/X86/urem-seteq-illegal-types.ll
    M llvm/test/CodeGen/X86/urem-seteq-vec-nonsplat.ll
    M llvm/test/CodeGen/X86/urem-seteq-vec-splat.ll
    M llvm/test/CodeGen/X86/vec_shift6.ll
    M llvm/test/CodeGen/X86/vector-fshl-128.ll
    M llvm/test/CodeGen/X86/vector-fshl-rot-128.ll
    M llvm/test/CodeGen/X86/vector-fshl-rot-256.ll
    M llvm/test/CodeGen/X86/vector-fshl-rot-sub128.ll
    M llvm/test/CodeGen/X86/vector-fshr-128.ll
    M llvm/test/CodeGen/X86/vector-fshr-rot-128.ll
    M llvm/test/CodeGen/X86/vector-fshr-rot-256.ll
    M llvm/test/CodeGen/X86/vector-fshr-rot-sub128.ll
    M llvm/test/CodeGen/X86/vector-mul.ll
    M llvm/test/CodeGen/X86/vector-rotate-128.ll
    M llvm/test/CodeGen/X86/vector-rotate-256.ll
    M llvm/test/CodeGen/X86/vector-shift-shl-128.ll
    M llvm/test/CodeGen/X86/vector-shuffle-combining.ll
    M llvm/test/CodeGen/X86/vector-trunc-math.ll

  Log Message:
  -----------
  [X86] combineX86ShufflesConstants - constant fold from target shuffles unless optsize = true

Currently we only constant fold target shuffles if any of the sources has one use, or it would remove a variable shuffle mask - the aim being to avoid constant pool bloat.

This patch proposes we should constant fold by default and only limit this if optsize is enabled - I've added a basic test for this in vector-mul.ll (the pmuludq case is by far the most common), I can add other specific test cases if people need them.

This should permit further constant folding, break some instruction dependencies and help reduce shuffle port pressure.

Differential Revision: https://reviews.llvm.org/D113748