[clang] [Clang] VectorExprEvaluator::VisitCallExpr / InterpretBuiltin - allow MMX/SSE/AVX2 PSIGN intrinsics to be used in constexpr (PR #163685)

[Simon Pilgrim via cfe-commits]

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@@ -3802,6 +3802,20 @@ bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const CallExpr *Call,
     return interp__builtin_ia32_movmsk_op(S, OpPC, Call);
   }
 
+  case X86::BI__builtin_ia32_psignb128:
+  case X86::BI__builtin_ia32_psignb256:
+  case X86::BI__builtin_ia32_psignw128:
+  case X86::BI__builtin_ia32_psignw256:
+  case X86::BI__builtin_ia32_psignd128:
+  case X86::BI__builtin_ia32_psignd256:
+    return interp__builtin_elementwise_int_binop(
+        S, OpPC, Call, [](const APSInt &AElem, const APSInt &BElem) -> APInt {
+          return BElem[BElem.getBitWidth() - 1]
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RKSimon wrote:

BElem.isNegative()?

https://github.com/llvm/llvm-project/pull/163685