[clang] [Clang] VectorExprEvaluator::VisitCallExpr / InterpretBuiltin - allow SSE41 phminposuw intrinsic to be used in constexp (PR #163041)

[Simon Pilgrim via cfe-commits]

================
@@ -3003,6 +3003,45 @@ static bool interp__builtin_x86_insert_subvector(InterpState &S, CodePtr OpPC,
   return true;
 }
 
+static bool interp__builtin_ia32_phminposuw(InterpState &S, CodePtr OpPC,
+                                            const CallExpr *Call) {
+  assert(Call->getNumArgs() == 1);
+
+  const Pointer &Source = S.Stk.pop<Pointer>();
+  const Pointer &Dest = S.Stk.peek<Pointer>();
+
+  unsigned SourceLen = Source.getNumElems();
+  QualType ElemQT = getElemType(Source);
+  OptPrimType ElemT = S.getContext().classify(ElemQT);
+  unsigned ElemBitWidth = S.getASTContext().getTypeSize(ElemQT);
+
+  bool DestUnsigned = Call->getCallReturnType(S.getASTContext())
+                          ->castAs<VectorType>()
+                          ->getElementType()
+                          ->isUnsignedIntegerOrEnumerationType();
+
+  INT_TYPE_SWITCH_NO_BOOL(*ElemT, {
+    APSInt MinIndex(ElemBitWidth, DestUnsigned);
----------------
RKSimon wrote:

Its probably better to just use:
```suggestion
    unsigned MinIndex = 0;
```
We never make use of APSInt/APInt features for the index.

https://github.com/llvm/llvm-project/pull/163041