CodeGen: Compound literals with funny types shouldn't crash

CodeGen assumed that a compound literal with array type should have a
corresponding LLVM IR array type.

We had two bugs in this area:
- Zero sized arrays in compound literals would lead to the creation of
  an opaque type.  This is unnecessary, we should just create an array
  type with a bound of zero.
- Funny record types (like unions) lead to exotic IR types for compound
  literals.  In this case, CodeGen must be prepared to deal with the
  possibility that it might not have an array IR type.

This fixes PR21912.

llvm-svn: 224219

clang/lib/CodeGen/CGExprConstant.cpp

@@ -1217,7 +1217,8 @@ llvm::Constant *CodeGenModule::EmitConstantValue(const APValue &Value,
                                           CAT->getElementType(), CGF);
 
     // Emit initializer elements.
-    llvm::Type *CommonElementType = nullptr;
+    llvm::Type *CommonElementType =
+        getTypes().ConvertType(CAT->getElementType());
     for (unsigned I = 0; I < NumElements; ++I) {
       llvm::Constant *C = Filler;
       if (I < NumInitElts)

clang/lib/CodeGen/CGExprScalar.cpp

@@ -1411,8 +1411,10 @@ Value *ScalarExprEmitter::VisitCastExpr(CastExpr *CE) {
     // anything here.
     if (!E->getType()->isVariableArrayType()) {
       assert(isa<llvm::PointerType>(V->getType()) && "Expected pointer");
-      assert(isa<llvm::ArrayType>(cast<llvm::PointerType>(V->getType())
-                                 ->getElementType()) &&
+      V = CGF.Builder.CreatePointerCast(
+          V, ConvertType(E->getType())->getPointerTo());
+
+      assert(isa<llvm::ArrayType>(V->getType()->getPointerElementType()) &&
              "Expected pointer to array");
       V = Builder.CreateStructGEP(V, 0, "arraydecay");
     }

clang/test/CodeGenCXX/compound-literals.cpp

@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -triple armv7-none-eabi -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -std=c++11 -triple armv7-none-eabi -emit-llvm -o - %s | FileCheck %s
 
 struct X {
   X();
@@ -42,3 +42,16 @@ struct Z { int i[3]; };
 int *p = (Z){ {1, 2, 3} }.i;
 // CHECK: define {{.*}}__cxx_global_var_init()
 // CHECK: store i32* getelementptr inbounds (%struct.Z* @.compoundliteral, i32 0, i32 0, i32 0), i32** @p
+
+
+int *PR21912_1 = (int []){};
+// CHECK-LABEL: define {{.*}}__cxx_global_var_init1()
+// CHECK: store i32* getelementptr inbounds ([0 x i32]* @.compoundliteral2, i32 0, i32 0), i32** @PR21912_1
+
+union PR21912Ty {
+  long long l;
+  double d;
+};
+union PR21912Ty *PR21912_2 = (union PR21912Ty[]){{.d = 2.0}, {.l = 3}};
+// CHECK-LABEL: define {{.*}}__cxx_global_var_init3()
+// CHECK: store %union.PR21912Ty* getelementptr inbounds ([2 x %union.PR21912Ty]* bitcast (<{ { double }, %union.PR21912Ty }>* @.compoundliteral4 to [2 x %union.PR21912Ty]*), i32 0, i32 0), %union.PR21912Ty** @PR21912_2

clang/test/CodeGenCXX/lambda-expressions.cpp

@@ -81,7 +81,7 @@ int g() {
 };
 
 // PR14773
-// CHECK: [[ARRVAL:%[0-9a-zA-Z]*]] = load i32* getelementptr inbounds ([0 x i32]* bitcast (<{}>* @_ZZ14staticarrayrefvE5array to [0 x i32]*), i32 0, i64 0), align 4
+// CHECK: [[ARRVAL:%[0-9a-zA-Z]*]] = load i32* getelementptr inbounds ([0 x i32]* @_ZZ14staticarrayrefvE5array, i32 0, i64 0), align 4
 // CHECK-NEXT: store i32 [[ARRVAL]]
 void staticarrayref(){
   static int array[] = {};