[all-commits] [llvm/llvm-project] c486b8: [x86] try harder to scalarize a vector load with e...

[Sanjay Patel via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: c486b82cfbe59929a80e5f29bab82112555c8bf4
      https://github.com/llvm/llvm-project/commit/c486b82cfbe59929a80e5f29bab82112555c8bf4
  Author: Sanjay Patel <spatel at rotateright.com>
  Date:   2022-02-13 (Sun, 13 Feb 2022)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/test/CodeGen/X86/2011-12-26-extractelement-duplicate-load.ll
    M llvm/test/CodeGen/X86/avx512-cvt.ll
    M llvm/test/CodeGen/X86/bitcast-vector-bool.ll
    M llvm/test/CodeGen/X86/extractelement-load.ll
    M llvm/test/CodeGen/X86/oddsubvector.ll
    M llvm/test/CodeGen/X86/pr45378.ll
    M llvm/test/CodeGen/X86/scalar_widen_div.ll
    M llvm/test/CodeGen/X86/shrink_vmul.ll
    M llvm/test/CodeGen/X86/vec_cast.ll
    M llvm/test/CodeGen/X86/vec_int_to_fp.ll

  Log Message:
  -----------
  [x86] try harder to scalarize a vector load with extracted integer op uses

This is a retry of b4b97ec813a0 - that was reverted because it
could cause miscompiles by illegally reordering memory operations.
A new test based on #53695 is added here to verify we do not have
that same problem.

extract_vec_elt (load X), C --> scalar load (X+C)

As noted in the comment, DAGCombiner has this fold -- and the code in this
patch is adapted from DAGCombiner::scalarizeExtractedVectorLoad() -- but
x86 should benefit even if the loaded vector has other uses as long as we
apply some other x86-specific conditions. The motivating example from #50310
is shown in vec_int_to_fp.ll.

Fixes #50310
Fixes #53695

Differential Revision: https://reviews.llvm.org/D118376