Simplify blend index calculation

Author: brandonxin

clang/lib/AST/ByteCode/InterpBuiltin.cpp

@@ -2845,11 +2845,8 @@ static bool interp__builtin_blend(InterpState &S, CodePtr OpPC,
   PrimType ElemT = FalseElem.getFieldDesc()->getPrimType();
   PrimType DstElemT = Dst.getFieldDesc()->getPrimType();
 
-  auto BitIndex = BuiltinID == X86::BI__builtin_ia32_pblendw256
-                      ? [](unsigned I) { return I % 8; }
-                      : [](unsigned I) { return I; };
   for (unsigned I = 0; I != NumElems; ++I) {
-    bool MaskBit = Mask[BitIndex(I)];
+    bool MaskBit = Mask[I % 8];
     if (ElemT == PT_Float) {
       assert(DstElemT == PT_Float);
       Dst.elem<Floating>(I) =

clang/lib/AST/ExprConstant.cpp

@@ -11967,13 +11967,10 @@ bool VectorExprEvaluator::VisitCallExpr(const CallExpr *E) {
     auto SourceLen = SourceF.getVectorLength();
     SmallVector<APValue, 32> ResultElements;
     ResultElements.reserve(SourceLen);
-    auto BitIndex = E->getBuiltinCallee() == X86::BI__builtin_ia32_pblendw256
-                        ? [](unsigned I) { return I % 8; }
-                        : [](unsigned I) { return I; };
     for (unsigned EltNum = 0; EltNum != SourceLen; ++EltNum) {
       const APValue &F = SourceF.getVectorElt(EltNum);
       const APValue &T = SourceT.getVectorElt(EltNum);
-      ResultElements.push_back(C[BitIndex(EltNum)] ? T : F);
+      ResultElements.push_back(C[EltNum % 8] ? T : F);
     }
 
     return Success(APValue(ResultElements.data(), ResultElements.size()), E);