[ExtVectorType] Support conditional select operator for C++.

This patch implements the conditional select operator for
ext_vector_types in C++. It does so by using the same semantics as for
C.

D71463 added support for the conditional select operator for VectorType
in C++. Unfortunately the semantics between ext_vector_type in C are
different to VectorType in C++. Select for ext_vector_type is based on
the MSB of the condition vector, whereas for VectorType it is `!= 0`.

This unfortunately means that the behavior is inconsistent between
ExtVectorType and VectorType, but I think using the C semantics for
ExtVectorType in C++ as well should be less surprising for users.

Reviewed By: erichkeane, aaron.ballman

Differential Revision: https://reviews.llvm.org/D98055

Author: fhahn

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -7478,9 +7478,10 @@ def err_conditional_vector_element_size : Error<
 def err_conditional_vector_has_void : Error<
   "GNU vector conditional operand cannot be %select{void|a throw expression}0">;
 def err_conditional_vector_operand_type
-    : Error<"%select{enumeration|extended vector}0 type %1 is not allowed in a "
-            "vector conditional">;
-def err_conditional_vector_mismatched_vectors
+    : Error<"enumeration type %0 is not allowed in a vector conditional">;
+def err_conditional_vector_cond_result_mismatch
+    : Error<"cannot mix vectors and extended vectors in a vector conditional">;
+def err_conditional_vector_mismatched
     : Error<"vector operands to the vector conditional must be the same type "
             "%diff{($ and $)|}0,1}">;
 

clang/include/clang/Sema/Sema.h

@@ -11474,9 +11474,9 @@ class Sema final {
   QualType CXXCheckConditionalOperands( // C++ 5.16
     ExprResult &cond, ExprResult &lhs, ExprResult &rhs,
     ExprValueKind &VK, ExprObjectKind &OK, SourceLocation questionLoc);
-  QualType CheckGNUVectorConditionalTypes(ExprResult &Cond, ExprResult &LHS,
-                                          ExprResult &RHS,
-                                          SourceLocation QuestionLoc);
+  QualType CheckVectorConditionalTypes(ExprResult &Cond, ExprResult &LHS,
+                                       ExprResult &RHS,
+                                       SourceLocation QuestionLoc);
   QualType FindCompositePointerType(SourceLocation Loc, Expr *&E1, Expr *&E2,
                                     bool ConvertArgs = true);
   QualType FindCompositePointerType(SourceLocation Loc,

clang/lib/Sema/SemaExprCXX.cpp

@@ -5918,19 +5918,18 @@ static bool ConvertForConditional(Sema &Self, ExprResult &E, QualType T) {
 // extension.
 static bool isValidVectorForConditionalCondition(ASTContext &Ctx,
                                                  QualType CondTy) {
-  if (!CondTy->isVectorType() || CondTy->isExtVectorType())
+  if (!CondTy->isVectorType() && !CondTy->isExtVectorType())
     return false;
   const QualType EltTy =
       cast<VectorType>(CondTy.getCanonicalType())->getElementType();
-
   assert(!EltTy->isBooleanType() && !EltTy->isEnumeralType() &&
          "Vectors cant be boolean or enum types");
   return EltTy->isIntegralType(Ctx);
 }
 
-QualType Sema::CheckGNUVectorConditionalTypes(ExprResult &Cond, ExprResult &LHS,
-                                              ExprResult &RHS,
-                                              SourceLocation QuestionLoc) {
+QualType Sema::CheckVectorConditionalTypes(ExprResult &Cond, ExprResult &LHS,
+                                           ExprResult &RHS,
+                                           SourceLocation QuestionLoc) {
   LHS = DefaultFunctionArrayLvalueConversion(LHS.get());
   RHS = DefaultFunctionArrayLvalueConversion(RHS.get());
 
@@ -5945,24 +5944,17 @@ QualType Sema::CheckGNUVectorConditionalTypes(ExprResult &Cond, ExprResult &LHS,
 
   QualType ResultType;
 
-  // FIXME: In the future we should define what the Extvector conditional
-  // operator looks like.
-  if (LHSVT && isa<ExtVectorType>(LHSVT)) {
-    Diag(QuestionLoc, diag::err_conditional_vector_operand_type)
-        << /*isExtVector*/ true << LHSType;
-    return {};
-  }
-
-  if (RHSVT && isa<ExtVectorType>(RHSVT)) {
-    Diag(QuestionLoc, diag::err_conditional_vector_operand_type)
-        << /*isExtVector*/ true << RHSType;
-    return {};
-  }
 
   if (LHSVT && RHSVT) {
+    if (isa<ExtVectorType>(CondVT) != isa<ExtVectorType>(LHSVT)) {
+      Diag(QuestionLoc, diag::err_conditional_vector_cond_result_mismatch)
+          << /*isExtVector*/ isa<ExtVectorType>(CondVT);
+      return {};
+    }
+
     // If both are vector types, they must be the same type.
     if (!Context.hasSameType(LHSType, RHSType)) {
-      Diag(QuestionLoc, diag::err_conditional_vector_mismatched_vectors)
+      Diag(QuestionLoc, diag::err_conditional_vector_mismatched)
           << LHSType << RHSType;
       return {};
     }
@@ -5987,18 +5979,22 @@ QualType Sema::CheckGNUVectorConditionalTypes(ExprResult &Cond, ExprResult &LHS,
 
     if (ResultElementTy->isEnumeralType()) {
       Diag(QuestionLoc, diag::err_conditional_vector_operand_type)
-          << /*isExtVector*/ false << ResultElementTy;
+          << ResultElementTy;
       return {};
     }
-    ResultType = Context.getVectorType(
-        ResultElementTy, CondType->castAs<VectorType>()->getNumElements(),
-        VectorType::GenericVector);
+    if (CondType->isExtVectorType())
+      ResultType =
+          Context.getExtVectorType(ResultElementTy, CondVT->getNumElements());
+    else
+      ResultType = Context.getVectorType(
+          ResultElementTy, CondVT->getNumElements(), VectorType::GenericVector);
 
     LHS = ImpCastExprToType(LHS.get(), ResultType, CK_VectorSplat);
     RHS = ImpCastExprToType(RHS.get(), ResultType, CK_VectorSplat);
   }
 
   assert(!ResultType.isNull() && ResultType->isVectorType() &&
+         (!CondType->isExtVectorType() || ResultType->isExtVectorType()) &&
          "Result should have been a vector type");
   auto *ResultVectorTy = ResultType->castAs<VectorType>();
   QualType ResultElementTy = ResultVectorTy->getElementType();
@@ -6025,15 +6021,21 @@ QualType Sema::CheckGNUVectorConditionalTypes(ExprResult &Cond, ExprResult &LHS,
 /// See C++ [expr.cond]. Note that LHS is never null, even for the GNU x ?: y
 /// extension. In this case, LHS == Cond. (But they're not aliases.)
 ///
-/// This function also implements GCC's vector extension for conditionals.
-///  GCC's vector extension permits the use of a?b:c where the type of
-///  a is that of a integer vector with the same number of elements and
-///  size as the vectors of b and c. If one of either b or c is a scalar
-///  it is implicitly converted to match the type of the vector.
-///  Otherwise the expression is ill-formed. If both b and c are scalars,
-///  then b and c are checked and converted to the type of a if possible.
-///  Unlike the OpenCL ?: operator, the expression is evaluated as
-///  (a[0] != 0 ? b[0] : c[0], .. , a[n] != 0 ? b[n] : c[n]).
+/// This function also implements GCC's vector extension and the
+/// OpenCL/ext_vector_type extension for conditionals. The vector extensions
+/// permit the use of a?b:c where the type of a is that of a integer vector with
+/// the same number of elements and size as the vectors of b and c. If one of
+/// either b or c is a scalar it is implicitly converted to match the type of
+/// the vector. Otherwise the expression is ill-formed. If both b and c are
+/// scalars, then b and c are checked and converted to the type of a if
+/// possible.
+///
+/// The expressions are evaluated differently for GCC's and OpenCL's extensions.
+/// For the GCC extension, the ?: operator is evaluated as
+///   (a[0] != 0 ? b[0] : c[0], .. , a[n] != 0 ? b[n] : c[n]).
+/// For the OpenCL extensions, the ?: operator is evaluated as
+///   (most-significant-bit-set(a[0])  ? b[0] : c[0], .. ,
+///    most-significant-bit-set(a[n]) ? b[n] : c[n]).
 QualType Sema::CXXCheckConditionalOperands(ExprResult &Cond, ExprResult &LHS,
                                            ExprResult &RHS, ExprValueKind &VK,
                                            ExprObjectKind &OK,
@@ -6117,7 +6119,7 @@ QualType Sema::CXXCheckConditionalOperands(ExprResult &Cond, ExprResult &LHS,
 
   // Neither is void.
   if (IsVectorConditional)
-    return CheckGNUVectorConditionalTypes(Cond, LHS, RHS, QuestionLoc);
+    return CheckVectorConditionalTypes(Cond, LHS, RHS, QuestionLoc);
 
   // C++11 [expr.cond]p3
   //   Otherwise, if the second and third operand have different types, and