[all-commits] [llvm/llvm-project] d92ce3: Revert faecc736e2ac3cd8c77 #74443 [DAG] isSplatVal...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: d92ce344bf641e6bb025b41b3f1a77dd25e2b3e9
      https://github.com/llvm/llvm-project/commit/d92ce344bf641e6bb025b41b3f1a77dd25e2b3e9
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2024-01-17 (Wed, 17 Jan 2024)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
    M llvm/test/CodeGen/ARM/vector-store.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-int-shuffles.ll
    M llvm/test/CodeGen/X86/fold-pcmpeqd-2.ll
    M llvm/test/CodeGen/X86/pr78109.ll
    M llvm/test/CodeGen/X86/var-permute-256.ll
    M llvm/test/CodeGen/X86/vector-interleaved-load-i8-stride-4.ll
    M llvm/test/CodeGen/X86/vector-interleaved-load-i8-stride-6.ll
    M llvm/test/CodeGen/X86/vector-shift-ashr-128.ll
    M llvm/test/CodeGen/X86/vector-shift-ashr-256.ll
    M llvm/test/CodeGen/X86/vector-shift-lshr-128.ll
    M llvm/test/CodeGen/X86/vector-shift-lshr-256.ll
    M llvm/test/CodeGen/X86/vector-shift-shl-128.ll
    M llvm/test/CodeGen/X86/vector-shift-shl-256.ll

  Log Message:
  -----------
  Revert faecc736e2ac3cd8c77 #74443 [DAG] isSplatValue - node is a splat if all demanded elts have the same whole constant value (#74443)

Relying on ComputeKnownBits to find a splat is causing miscompilations where a shift of zero is being assumed to give zero, but further simplification leads to a shift of zero by undef, resulting in an unexpected undef value.

Fixes #78109