[all-commits] [llvm/llvm-project] 469caa: [RISCV] Use vwadd.vx for splat vector with extensi...

[Chia via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 469caa31e77f1da37434783f9b4f1d87fe8dff71
      https://github.com/llvm/llvm-project/commit/469caa31e77f1da37434783f9b4f1d87fe8dff71
  Author: Chia <sun1011jacobi at gmail.com>
  Date:   2024-04-10 (Wed, 10 Apr 2024)

  Changed paths:
    M llvm/lib/Target/RISCV/RISCVISelLowering.cpp
    M llvm/test/CodeGen/RISCV/rvv/ctlz-sdnode.ll
    M llvm/test/CodeGen/RISCV/rvv/cttz-sdnode.ll
    M llvm/test/CodeGen/RISCV/rvv/vwadd-sdnode.ll
    M llvm/test/CodeGen/RISCV/rvv/vwsll-sdnode.ll

  Log Message:
  -----------
  [RISCV] Use vwadd.vx for splat vector with extension (#87249)

This patch allows `combineBinOp_VLToVWBinOp_VL` to handle patterns like
`(splat_vector (sext op))` or `(splat_vector (zext op))`. Then we can
use `vwadd.vx` and `vwadd.w` for such a case.

### Source code
```
define <vscale x 8 x i64> @vwadd_vx_splat_sext(<vscale x 8 x i32> %va, i32 %b) {
     %sb = sext i32 %b to i64
     %head = insertelement <vscale x 8 x i64> poison, i64 %sb, i32 0
     %splat = shufflevector <vscale x 8 x i64> %head, <vscale x 8 x i64> poison, <vscale x 8 x i32> zeroinitializer
     %vc = sext <vscale x 8 x i32> %va to <vscale x 8 x i64>
     %ve = add <vscale x 8 x i64> %vc, %splat
     ret <vscale x 8 x i64> %ve
}
```

### Before this patch
[Compiler Explorer](https://godbolt.org/z/sq191PsT4)
```
vwadd_vx_splat_sext:
  sext.w a0, a0
  vsetvli a1, zero, e64, m8, ta, ma
  vmv.v.x v16, a0
  vsetvli zero, zero, e32, m4, ta, ma
  vwadd.wv v16, v16, v8
  vmv8r.v v8, v16
  ret
```
### After this patch
```
vwadd_vx_splat_sext
  vsetvli a1, zero, e32, m4, ta, ma
  vwadd.vx v16, v8, a0
  vmv8r.v v8, v16
  ret
```



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