[llvm] [msan] Handle Arm NEON saturating extract and narrow (PR #125742)

[Florian Mayer via llvm-commits]

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@@ -4749,6 +4749,13 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
       setOrigin(&I, getCleanOrigin());
       break;
 
+    // Saturating extract narrow
+    case Intrinsic::aarch64_neon_sqxtn:
+    case Intrinsic::aarch64_neon_sqxtun:
+    case Intrinsic::aarch64_neon_uqxtn:
+      handleShadowOr(I);
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fmayer wrote:

Isn't the output only half as long as the original? Don't we need to account for that?

Also, it is confusing that you use `handleShadowOr` on a single argument instruction. At least leave a comment that explains.

https://github.com/llvm/llvm-project/pull/125742