[llvm-bugs] [Bug 49055] New: [X86] or/add-like mismatch in uchar 'splat' to uint

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=49055

            Bug ID: 49055
           Summary: [X86] or/add-like mismatch in uchar 'splat' to uint
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Common Code Generator Code
          Assignee: unassignedbugs at nondot.org
          Reporter: llvm-dev at redking.me.uk
                CC: craig.topper at gmail.com, lebedev.ri at gmail.com,
                    llvm-bugs at lists.llvm.org, spatel+llvm at rotateright.com

https://simd.godbolt.org/z/E15MrP

void loop_add(const unsigned char* __restrict pIn, unsigned int* __restrict
pOut, int s) {
  for (int i = 0; i < s; i++) {
    unsigned int pixelChar = pIn[i];
    unsigned int pixel = pixelChar + (pixelChar << 8) + (pixelChar << 16) +
(255 << 24);
    pOut[i] = pixel;
  }
}

This successfully combines to a zext+mul+add (I think technically it could be
zext+mul+or)?

But this:

void loop_or(const unsigned char* __restrict pIn, unsigned int* __restrict
pOut, int s) {
  for (int i = 0; i < s; i++) {
    unsigned int pixelChar = pIn[i];
    unsigned int pixel = pixelChar | (pixelChar << 8) | (pixelChar << 16) |
(255 << 24);
    pOut[i] = pixel;
  }
}

completely fails and we end up with a long shift+or chain.

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