[clang] [X86] Add constexpr support for addsub intrinsics (PR #167512)

[Ahmed Nour via cfe-commits]

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@@ -13373,6 +13373,35 @@ bool VectorExprEvaluator::VisitCallExpr(const CallExpr *E) {
     }
     return Success(APValue(ResultElements.data(), ResultElements.size()), E);
   }
+  case clang::X86::BI__builtin_ia32_addsubpd:
+  case clang::X86::BI__builtin_ia32_addsubps:
+  case clang::X86::BI__builtin_ia32_addsubpd256:
+  case clang::X86::BI__builtin_ia32_addsubps256: {
+    // Addsub: alternates between subtraction and addition
+    // Result[i] = (i % 2 == 0) ? (a[i] - b[i]) : (a[i] + b[i])
+    APValue SourceLHS, SourceRHS;
+    if (!EvaluateAsRValue(Info, E->getArg(0), SourceLHS) ||
+        !EvaluateAsRValue(Info, E->getArg(1), SourceRHS))
+      return false;
+    unsigned NumElts = SourceLHS.getVectorLength();
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ahmednoursphinx wrote:

Updated , Good catch, i should have aligned with `InterpBuiltin.cpp` convention

https://github.com/llvm/llvm-project/pull/167512