[llvm-bugs] [Bug 45314] New: Redundant vmov{q, d} before 32-bit splat

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=45314

            Bug ID: 45314
           Summary: Redundant vmov{q,d} before 32-bit splat
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: daan at dsprenkels.com
                CC: craig.topper at gmail.com, llvm-bugs at lists.llvm.org,
                    llvm-dev at redking.me.uk, spatel+llvm at rotateright.com

The following code:

```
#include <immintrin.h>

__m256i broadcast(const __m256i x) {
    return _mm256_set_epi32(x[0], x[0], x[0], x[0], x[0], x[0], x[0], x[0]);
}
```

is compiled to:

```
broadcast:                              # @broadcast
        vmovq   rax, xmm0
        vmovd   xmm0, eax
        vpbroadcastd    ymm0, xmm0
        ret
```

These two vmov operations are redundant.

GCC already omits these operations:

```
broadcast:
        vpbroadcastd    ymm0, xmm0
        ret
```

Godbolt link: https://c.godbolt.org/z/bkVDWj

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