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

[Vitaly Buka via llvm-commits]

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@@ -2618,28 +2625,54 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
     FixedVectorType *ParamType =
         cast<FixedVectorType>(I.getArgOperand(0)->getType());
     if (I.arg_size() == 2)
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vitalybuka wrote:

     assert(I.arg_size() != 2 || I.getArgOperand(0)->getType() == I.getArgOperand(1)->getType());

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