Jessica Paquette 5c26be214d [AArch64][GlobalISel] Lower G_BUILD_VECTOR -> G_DUP ...

If we have

```
%vec = G_BUILD_VECTOR %reg, %reg, ..., %reg
```

Then lower it to

```
%vec = G_DUP %reg
```

Also update the selector to handle constant splats on G_DUP.

This will not combine when the splat is all zeros or ones. Tablegen-imported
patterns rely on these being G_BUILD_VECTOR.

Minor code size improvements on CTMark at -Os.

Also adds some utility functions to make it a bit easier to recognize splats,
and an AArch64-specific splat helper.

Differential Revision: https://reviews.llvm.org/D97731

2021-03-08 13:01:10 -08:00

30 KiB

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