implement codegen support for aggregates casted to void.

llvm-svn: 47226

clang/CodeGen/CGExprScalar.cpp

@@ -508,18 +508,26 @@ Value *ScalarExprEmitter::VisitImplicitCastExpr(const ImplicitCastExpr *E) {
 // handle things like function to ptr-to-function decay etc.
 Value *ScalarExprEmitter::EmitCastExpr(const Expr *E, QualType DestTy) {
   // Handle cases where the source is an non-complex type.
-  if (!E->getType()->isComplexType()) {
+  
+  if (!CGF.hasAggregateLLVMType(E->getType())) {
     Value *Src = Visit(const_cast<Expr*>(E));
 
     // Use EmitScalarConversion to perform the conversion.
     return EmitScalarConversion(Src, E->getType(), DestTy);
   }
   
+  if (E->getType()->isComplexType()) {
     // Handle cases where the source is a complex type.
     return EmitComplexToScalarConversion(CGF.EmitComplexExpr(E), E->getType(),
                                          DestTy);
   }
 
+  // Okay, this is a cast from an aggregate.  It must be a cast to void.  Just
+  // evaluate the result and return.
+  CGF.EmitAggExpr(E, 0, false);
+  return 0;
+}
+
 Value *ScalarExprEmitter::VisitStmtExpr(const StmtExpr *E) {
   return CGF.EmitCompoundStmt(*E->getSubStmt(), true).getScalarVal();
 }

clang/test/CodeGen/compound.c

@@ -1,4 +1,4 @@
-// RUN: clang %s -emit-llvm
+// RUN: clang < %s -emit-llvm
 int A;
 long long B;
 int C;
@@ -18,3 +18,8 @@ void foo(char *strbuf) {
   int stufflen = 4;
   strbuf += stufflen;
 }
+
+
+// Aggregate cast to void
+union uu { int a;}; void f(union uu p) { (void) p;}
+