[all-commits] [llvm/llvm-project] bc78ba: [X86] Improve combineVectorShiftImm

[jayfoad via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: bc78baec4cc3ac95a931f4708f1534af7ff77de5
      https://github.com/llvm/llvm-project/commit/bc78baec4cc3ac95a931f4708f1534af7ff77de5
  Author: Jay Foad <jay.foad at amd.com>
  Date:   2020-04-13 (Mon, 13 Apr 2020)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/test/CodeGen/X86/midpoint-int-vec-128.ll
    M llvm/test/CodeGen/X86/midpoint-int-vec-256.ll
    M llvm/test/CodeGen/X86/midpoint-int-vec-512.ll

  Log Message:
  -----------
  [X86] Improve combineVectorShiftImm

Summary:
Fold (shift (shift X, C2), C1) -> (shift X, (C1 + C2)) for logical as
well as arithmetic shifts. This is needed to prevent regressions from
an upcoming funnel shift expansion change.

While we're here, fold (VSRAI -1, C) -> -1 too.

Reviewers: RKSimon, craig.topper

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D77300