[llvm] [LoongArch] Try to widen shuffle mask (PR #136081)

[via llvm-commits]

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@@ -6,7 +6,8 @@ define <32 x i8> @widen_shuffle_mask_v32i8_to_v16i16(<32 x i8> %a, <32 x i8> %b)
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    pcalau12i $a0, %pc_hi20(.LCPI0_0)
 ; CHECK-NEXT:    xvld $xr2, $a0, %pc_lo12(.LCPI0_0)
-; CHECK-NEXT:    xvshuf.b $xr0, $xr1, $xr0, $xr2
+; CHECK-NEXT:    xvshuf.h $xr2, $xr1, $xr0
+; CHECK-NEXT:    xvori.b $xr0, $xr2, 0
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tangaac wrote:

Thanks, `xvori.b` is indeed redundant.
May we should use pointer instead vector in these lasx ir tests.

```llvm
define void @widen_shuffle_mask_v32i8_to_v16i16(ptr %a, ptr %b, ptr %c) {
; CHECK-LABEL: widen_shuffle_mask_v32i8_to_v16i16:
; CHECK:       # %bb.0:
; CHECK-NEXT:    xvld	$xr1, $a0, 0
; CHECK-NEXT:    xvld	$xr2, $a1, 0
; CHECK-NEXT:    pcalau12i	$a0, %pc_hi20(.LCPI0_0)
; CHECK-NEXT:    xvld $xr0, $a0, %pc_lo12(.LCPI0_0)
; CHECK-NEXT:    xvshuf.h $xr0, $xr2, $xr1
; CHECK-NEXT:    ret
    %1 = load <32 x i8>, ptr %a
    %2 = load <32 x i8>, ptr %b
    %r = shufflevector <32 x i8> %1, <32 x i8> %2, <32 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 32, i32 33, i32 34, i32 35, i32 24, i32 25, i32 26, i32 27, i32 48, i32 49, i32 50, i32 51, i32 52, i32 53, i32 54, i32 55, i32 60, i32 61, i32 30, i32 31>
    store <32 x i8> %r, ptr %c
    ret void
}
```

https://github.com/llvm/llvm-project/pull/136081