[all-commits] [llvm/llvm-project] f36804: [DAGCombiner] try to move splat after binop with s...

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  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: f368040c14f4bdac718798db28299a68adc42695
      https://github.com/llvm/llvm-project/commit/f368040c14f4bdac718798db28299a68adc42695
  Author: Sanjay Patel <spatel at rotateright.com>
  Date:   2020-05-26 (Tue, 26 May 2020)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/test/CodeGen/X86/vector-fshl-128.ll
    M llvm/test/CodeGen/X86/vector-fshl-256.ll
    M llvm/test/CodeGen/X86/vector-fshl-512.ll
    M llvm/test/CodeGen/X86/vector-fshl-rot-128.ll
    M llvm/test/CodeGen/X86/vector-fshr-128.ll
    M llvm/test/CodeGen/X86/vector-fshr-256.ll
    M llvm/test/CodeGen/X86/vector-fshr-512.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-rotate-128.ll
    M llvm/test/CodeGen/X86/vector-shift-ashr-128.ll
    M llvm/test/CodeGen/X86/vector-shift-lshr-128.ll

  Log Message:
  -----------
  [DAGCombiner] try to move splat after binop with splat constant

binop (splat X), (splat C) --> splat (binop X, C)
binop (splat C), (splat X) --> splat (binop C, X)

We do this in IR, and there's a similar fold for the case with 2
non-constant operands just above the code diff in this patch.

This was discussed in D79718, and the extra shuffle in the test
(llvm/test/CodeGen/X86/vector-fshl-128.ll::sink_splatvar) where it
was noticed disappears because demanded elements analysis is no
longer blocked. The large majority of the test diffs seem to be
benign code scheduling changes, but I do see another type of win:
moving the splat later allows binop narrowing in some cases.

Regressions were avoided on x86 and ARM with the INSERT_VECTOR_ELT
restriction.

Differential Revision: https://reviews.llvm.org/D79886