Merge commit 35ecc7fe4 from llvm git (by Hubert Tong):

[clang][Sema] Fix PR47676: Handle dependent AltiVec C-style cast

  Fix premature decision in the presence of type-dependent expression
  operands on whether AltiVec vector initializations from single
  expressions are "splat" operations.

  Verify that the instantiation is able to determine the correct cast
  semantics for both the scalar type and the vector type case.

  Note that, because the change only affects the single-expression case
  (and the target type is an AltiVec-style vector type), the
  replacement of a parenthesized list with a parenthesized expression
  does not change the semantics of the program in a program-observable
  manner.

  Reviewed By: aaron.ballman

  Differential Revision: https://reviews.llvm.org/D88526

This should fix 'Assertion failed: (isScalarType()), function
getScalarTypeKind, file /usr/src/contrib/llvm-project/clang/lib/AST
/Type.cpp, line 2146', when building the graphics/opencv-core port for
powerpc64le.

Requested by:	pkubaj
MFC after:	4 weeks
X-MFC-With:	r364284

contrib/llvm-project/clang/lib/Sema/SemaExpr.cpp

@@ -7402,7 +7402,7 @@ Sema::ActOnCastExpr(Scope *S, SourceLocation LParenLoc,
     }
     if (PE || PLE->getNumExprs() == 1) {
       Expr *E = (PE ? PE->getSubExpr() : PLE->getExpr(0));
-      if (!E->getType()->isVectorType())
+      if (!E->isTypeDependent() && !E->getType()->isVectorType())
         isVectorLiteral = true;
     }
     else