[llvm] [msan] Generalize handlePairwiseShadowOrIntrinsic, and handle x86 pairwise add/sub (PR #127567)

[Thurston Dang via llvm-commits]

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@@ -2653,6 +2688,7 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
     OrShadow = CreateShadowCast(IRB, OrShadow, getShadowTy(&I));
 
     setShadow(&I, OrShadow);
+
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thurstond wrote:

Removed

https://github.com/llvm/llvm-project/pull/127567