[llvm] [SelectionDAG] Add GET_ACTIVE_LANE_MASK to ComputeNumSignBits (PR #208977)

[Paul Walker via llvm-commits]

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@@ -17,3 +17,34 @@ entry:
   %data = call <16 x i8> @llvm.masked.load.v16i8.p0(ptr %p, i32 1, <16 x i1> %mask, <16 x i8> zeroinitializer)
   ret <16 x i8> %data
 }
+
+define void @active_lane_mask_mstore_vscaleX2(ptr %p, i64 %n) #0 {
+; CHECK-LABEL: active_lane_mask_mstore_vscaleX2:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    whilelo p0.b, xzr, x1
+; CHECK-NEXT:    mov z0.h, #123 // =0x7b
+; CHECK-NEXT:    punpklo p0.h, p0.b
+; CHECK-NEXT:    st1h { z0.h }, p0, [x0]
+; CHECK-NEXT:    ret
+entry:
+  %mask = call <16 x i1> @llvm.get.active.lane.mask.v16i1(i64 0, i64 %n)
+  call void @llvm.masked.store.v16i16.p0(<16 x i16> splat(i16 123), ptr %p, <16 x i1> %mask)
+  ret void
+}
+
+define void @active_lane_mask_mstore_vscaleX4(ptr %p, i64 %n) #1 {
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paulwalker-arm wrote:

```suggestion
define void @active_lane_mask_mstore_vscaleX4(ptr %p, i64 %n) vscale_range(4,4) {
```

https://github.com/llvm/llvm-project/pull/208977