splat cast wip

Author: spall

clang/include/clang/AST/OperationKinds.def

@@ -370,6 +370,9 @@ CAST_OPERATION(HLSLArrayRValue)
 // Aggregate by Value cast (HLSL only).
 CAST_OPERATION(HLSLAggregateCast)
 
+// Splat cast for Aggregates (HLSL only).
+CAST_OPERATION(HLSLSplatCast)
+
 //===- Binary Operations  -------------------------------------------------===//
 // Operators listed in order of precedence.
 // Note that additions to this should also update the StmtVisitor class,

clang/include/clang/Sema/SemaHLSL.h

@@ -142,6 +142,7 @@ class SemaHLSL : public SemaBase {
 
   bool CanPerformScalarCast(QualType SrcTy, QualType DestTy);
   bool CanPerformAggregateCast(Expr *Src, QualType DestType);
+  bool CanPerformSplat(Expr *Src, QualType DestType);
   ExprResult ActOnOutParamExpr(ParmVarDecl *Param, Expr *Arg);
 
   QualType getInoutParameterType(QualType Ty);

clang/lib/CodeGen/CGExprAgg.cpp

@@ -491,6 +491,33 @@ static bool isTrivialFiller(Expr *E) {
   return false;
 }
 
+static void EmitHLSLSplatCast(CodeGenFunction &CGF, Address DestVal,
+			      QualType DestTy, llvm::Value *SrcVal,
+			      QualType SrcTy, SourceLocation Loc) {
+  // Flatten our destination
+  SmallVector<QualType> DestTypes; // Flattened type
+  SmallVector<llvm::Value *, 4> IdxList;
+  SmallVector<std::pair<Address, llvm::Value *>, 16> StoreGEPList;
+  // ^^ Flattened accesses to DestVal we want to store into
+  CGF.FlattenAccessAndType(DestVal, DestTy, IdxList, StoreGEPList,
+		       DestTypes);
+
+  if (const VectorType *VT = SrcTy->getAs<VectorType>()) {
+    assert(VT->getNumElements() == 1 && "Invalid HLSL splat cast.");
+
+    SrcTy = VT->getElementType();
+    SrcVal = CGF.Builder.CreateExtractElement(SrcVal, (uint64_t)0,
+					      "vec.load");
+  }
+  assert(SrcTy->isScalarType() && "Invalid HLSL splat cast.");
+  for(unsigned i = 0; i < StoreGEPList.size(); i ++) {
+    llvm::Value *Cast = CGF.EmitScalarConversion(SrcVal, SrcTy,
+						 DestTypes[i],
+						 Loc);
+    CGF.PerformStore(StoreGEPList[i], Cast);
+  }
+}
+
 // emit a flat cast where the RHS is a scalar, including vector
 static void EmitHLSLScalarFlatCast(CodeGenFunction &CGF, Address DestVal,
                                    QualType DestTy, llvm::Value *SrcVal,
@@ -965,6 +992,21 @@ void AggExprEmitter::VisitCastExpr(CastExpr *E) {
   case CK_HLSLArrayRValue:
     Visit(E->getSubExpr());
     break;
+  case CK_HLSLSplatCast: {
+    Expr *Src = E->getSubExpr();
+    QualType SrcTy = Src->getType();
+    RValue RV = CGF.EmitAnyExpr(Src);
+    QualType DestTy = E->getType();
+    Address DestVal = Dest.getAddress();
+    SourceLocation Loc = E->getExprLoc();
+    
+    if (RV.isScalar()) {
+      llvm::Value *SrcVal = RV.getScalarVal();
+      EmitHLSLSplatCast(CGF, DestVal, DestTy, SrcVal, SrcTy, Loc);
+      break;
+    }
+    llvm_unreachable("RHS of HLSL splat cast must be a scalar or vector.");
+  }
   case CK_HLSLAggregateCast: {
     Expr *Src = E->getSubExpr();
     QualType SrcTy = Src->getType();

clang/lib/CodeGen/CGExprScalar.cpp

@@ -2787,6 +2787,22 @@ Value *ScalarExprEmitter::VisitCastExpr(CastExpr *CE) {
     llvm::Value *Zero = llvm::Constant::getNullValue(CGF.SizeTy);
     return Builder.CreateExtractElement(Vec, Zero, "cast.vtrunc");
   }
+  case CK_HLSLSplatCast: {
+    assert(DestTy->isVectorType() && "Destination type must be a vector.");
+    auto *DestVecTy = DestTy->getAs<VectorType>();
+    QualType SrcTy = E->getType();
+    SourceLocation Loc = CE->getExprLoc();
+    Value *V = Visit(const_cast<Expr *>(E));
+    if (auto *VecTy = SrcTy->getAs<VectorType>()) {
+      assert(VecTy->getNumElements() == 1 && "Invalid HLSL splat cast.");
+      V = CGF.Builder.CreateExtractElement(V, (uint64_t)0, "vec.load");
+      SrcTy = VecTy->getElementType();
+    }
+    assert(SrcTy->isScalarType() && "Invalid HLSL splat cast.");
+    Value *Cast = EmitScalarConversion(V, SrcTy,
+				       DestVecTy->getElementType(), Loc);
+    return Builder.CreateVectorSplat(DestVecTy->getNumElements(), Cast, "splat");
+  }
   case CK_HLSLAggregateCast: {
     RValue RV = CGF.EmitAnyExpr(E);
     SourceLocation Loc = CE->getExprLoc();

clang/lib/Sema/Sema.cpp

@@ -708,6 +708,7 @@ ExprResult Sema::ImpCastExprToType(Expr *E, QualType Ty,
     case CK_NonAtomicToAtomic:
     case CK_HLSLArrayRValue:
     case CK_HLSLAggregateCast:
+    case CK_HLSLSplatCast:
       break;
     }
   }

clang/lib/Sema/SemaCast.cpp

@@ -2772,9 +2772,16 @@ void CastOperation::CheckCXXCStyleCast(bool FunctionalStyle,
   CheckedConversionKind CCK = FunctionalStyle
                                   ? CheckedConversionKind::FunctionalCast
                                   : CheckedConversionKind::CStyleCast;
+
   // This case should not trigger on regular vector splat
-  // vector cast, vector truncation, or special hlsl splat cases
   QualType SrcTy = SrcExpr.get()->getType();
+  if (Self.getLangOpts().HLSL &&
+      Self.HLSL().CanPerformSplat(SrcExpr.get(), DestType)) {
+    Kind = CK_HLSLSplatCast;
+    return;
+  }
+
+  // This case should not trigger on regular vector cast, vector truncation
   if (Self.getLangOpts().HLSL &&
       Self.HLSL().CanPerformAggregateCast(SrcExpr.get(), DestType)) {
     if (SrcTy->isConstantArrayType())

clang/lib/Sema/SemaHLSL.cpp

@@ -2476,6 +2476,32 @@ bool SemaHLSL::CanPerformScalarCast(QualType SrcTy, QualType DestTy) {
   llvm_unreachable("Unhandled scalar cast");
 }
 
+// Can perform an HLSL splat cast if the Dest is an aggregate and the
+// Src is a scalar or a vector of length 1
+// Or if Dest is a vector and Src is a vector of length 1
+bool SemaHLSL::CanPerformSplat(Expr *Src, QualType DestTy) {
+
+  QualType SrcTy = Src->getType();
+  if (SrcTy->isScalarType() && DestTy->isVectorType())
+    return false;
+
+  const VectorType *SrcVecTy = SrcTy->getAs<VectorType>();
+  if (!(SrcTy->isScalarType() || (SrcVecTy && SrcVecTy->getNumElements() == 1)))
+    return false;
+
+  if (SrcVecTy)
+    SrcTy = SrcVecTy->getElementType();
+
+  llvm::SmallVector<QualType> DestTypes;
+  BuildFlattenedTypeList(DestTy, DestTypes);
+
+  for(unsigned i = 0; i < DestTypes.size(); i ++) {
+    if (!CanPerformScalarCast(SrcTy, DestTypes[i]))
+      return false;
+  }
+  return true;
+}
+
 // Can we perform an HLSL Flattened cast?
 // TODO: update this code when matrices are added
 bool SemaHLSL::CanPerformAggregateCast(Expr *Src, QualType DestTy) {