address PR comments add some todos that need to be addressed

Author: spall

clang/lib/AST/ExprConstant.cpp

@@ -14857,6 +14857,7 @@ bool IntExprEvaluator::VisitCastExpr(const CastExpr *E) {
   case CK_FixedPointCast:
   case CK_IntegralToFixedPoint:
   case CK_MatrixCast:
+    // TODO does CK_HLSLAggregateCast belong here?
     llvm_unreachable("invalid cast kind for integral value");
 
   case CK_BitCast:

clang/lib/CodeGen/CGExprAgg.cpp

@@ -1538,6 +1538,7 @@ static bool castPreservesZero(const CastExpr *CE) {
   case CK_NonAtomicToAtomic:
   case CK_AtomicToNonAtomic:
   case CK_HLSLVectorTruncation:
+    // TODO does CK_HLSLAggregateCast preserve zero?
     return true;
 
   case CK_BaseToDerivedMemberPointer:

clang/lib/Sema/SemaHLSL.cpp

@@ -2420,47 +2420,31 @@ bool SemaHLSL::CanPerformScalarCast(QualType SrcTy, QualType DestTy) {
 
   switch (Type::ScalarTypeKind SrcKind = SrcTy->getScalarTypeKind()) {
   case Type::STK_MemberPointer:
-    return false;
-
   case Type::STK_CPointer:
   case Type::STK_BlockPointer:
   case Type::STK_ObjCObjectPointer:
-    switch (DestTy->getScalarTypeKind()) {
-    case Type::STK_CPointer:
-    case Type::STK_BlockPointer:
-    case Type::STK_ObjCObjectPointer:
-    case Type::STK_Bool:
-    case Type::STK_Integral:
-      return true;
-    case Type::STK_Floating:
-    case Type::STK_FloatingComplex:
-    case Type::STK_IntegralComplex:
-    case Type::STK_MemberPointer:
-      return false;
-    case Type::STK_FixedPoint:
-      llvm_unreachable("HLSL doesn't have fixed point types.");
-    }
-    llvm_unreachable("Should have returned before this");
+    llvm_unreachable("HLSL doesn't support pointers.");
 
   case Type::STK_FixedPoint:
-    llvm_unreachable("HLSL doesn't have fixed point types.");
+    llvm_unreachable("HLSL doesn't support fixed point types.");
 
   case Type::STK_Bool: // casting from bool is like casting from an integer
   case Type::STK_Integral:
     switch (DestTy->getScalarTypeKind()) {
     case Type::STK_CPointer:
     case Type::STK_ObjCObjectPointer:
     case Type::STK_BlockPointer:
+    case Type::STK_MemberPointer:
+      llvm_unreachable("HLSL doesn't support pointers.");
     case Type::STK_Bool:
     case Type::STK_Integral:
     case Type::STK_Floating:
+      return true;
     case Type::STK_IntegralComplex:
     case Type::STK_FloatingComplex:
-      return true;
+      llvm_unreachable("HLSL doesn't support complex types.");
     case Type::STK_FixedPoint:
-      llvm_unreachable("HLSL doesn't have fixed point types.");
-    case Type::STK_MemberPointer:
-      return false;
+      llvm_unreachable("HLSL doesn't support fixed point types.");
     }
     llvm_unreachable("Should have returned before this");
 
@@ -2469,60 +2453,30 @@ bool SemaHLSL::CanPerformScalarCast(QualType SrcTy, QualType DestTy) {
     case Type::STK_Floating:
     case Type::STK_Bool:
     case Type::STK_Integral:
+      return true;
     case Type::STK_FloatingComplex:
     case Type::STK_IntegralComplex:
-      return true;
+      llvm_unreachable("HLSL doesn't support complex types.");
     case Type::STK_FixedPoint:
-      llvm_unreachable("HLSL doesn't have fixed point types.");
+      llvm_unreachable("HLSL doesn't support fixed point types.");
     case Type::STK_CPointer:
     case Type::STK_ObjCObjectPointer:
     case Type::STK_BlockPointer:
     case Type::STK_MemberPointer:
-      return false;
+      llvm_unreachable("HLSL doesn't support pointers.");
     }
     llvm_unreachable("Should have returned before this");
 
   case Type::STK_FloatingComplex:
-    switch (DestTy->getScalarTypeKind()) {
-    case Type::STK_FloatingComplex:
-    case Type::STK_IntegralComplex:
-    case Type::STK_Floating:
-    case Type::STK_Bool:
-    case Type::STK_Integral:
-      return true;
-    case Type::STK_CPointer:
-    case Type::STK_ObjCObjectPointer:
-    case Type::STK_BlockPointer:
-    case Type::STK_MemberPointer:
-      return false;
-    case Type::STK_FixedPoint:
-      llvm_unreachable("HLSL doesn't have fixed point types.");
-    }
-    llvm_unreachable("Should have returned before this");
-
   case Type::STK_IntegralComplex:
-    switch (DestTy->getScalarTypeKind()) {
-    case Type::STK_FloatingComplex:
-    case Type::STK_IntegralComplex:
-    case Type::STK_Integral:
-    case Type::STK_Bool:
-    case Type::STK_Floating:
-      return true;
-    case Type::STK_CPointer:
-    case Type::STK_ObjCObjectPointer:
-    case Type::STK_BlockPointer:
-    case Type::STK_MemberPointer:
-      return false;
-    case Type::STK_FixedPoint:
-      llvm_unreachable("HLSL doesn't have fixed point types.");
-    }
-    llvm_unreachable("Should have returned before this");
+    llvm_unreachable("HLSL doesn't support complex types.");
   }
 
   llvm_unreachable("Unhandled scalar cast");
 }
 
 // Can we perform an HLSL Flattened cast?
+// TODO: update this code when matrices are added
 bool SemaHLSL::CanPerformAggregateCast(Expr *Src, QualType DestTy) {
 
   // Don't handle casts where LHS and RHS are any combination of scalar/vector
@@ -2531,8 +2485,8 @@ bool SemaHLSL::CanPerformAggregateCast(Expr *Src, QualType DestTy) {
   if (SrcTy->isScalarType()) // always a splat and this cast doesn't handle that
     return false;
 
-  if ((DestTy->isScalarType() || DestTy->isVectorType()) &&
-      (SrcTy->isScalarType() || SrcTy->isVectorType()))
+  if (SrcTy->isVectorType() &&
+      (DestTy->isScalarType() || DestTy->isVectorType()))
     return false;
 
   llvm::SmallVector<QualType> DestTypes;
@@ -2542,18 +2496,15 @@ bool SemaHLSL::CanPerformAggregateCast(Expr *Src, QualType DestTy) {
 
   // Usually the size of SrcTypes must be greater than or equal to the size of
   // DestTypes.
-  if (SrcTypes.size() >= DestTypes.size()) {
+  if (SrcTypes.size() < DestTypes.size())
+    return false;
 
-    unsigned i;
-    for (i = 0; i < DestTypes.size() && i < SrcTypes.size(); i++) {
-      if (!CanPerformScalarCast(SrcTypes[i], DestTypes[i])) {
-        return false;
-      }
+  for (unsigned i = 0; i < DestTypes.size() && i < SrcTypes.size(); i++) {
+    if (!CanPerformScalarCast(SrcTypes[i], DestTypes[i])) {
+      return false;
     }
-    return true;
-  } else { // can't cast, Src is wrong size for Dest
-    return false;
   }
+  return true;
 }
 
 ExprResult SemaHLSL::ActOnOutParamExpr(ParmVarDecl *Param, Expr *Arg) {