From: Douglas Gregor <dgregor@apple.com>
Date: Thu, 15 Jul 2010 18:04:13 +0000 (+0000)
Subject: Teach CodeGenFunction::EmitCastLValue() to handle casts to an lvalue
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=5467209f23097d5b0fc628c18aaa85e73d386598;p=clang

Teach CodeGenFunction::EmitCastLValue() to handle casts to an lvalue
that involve binding a reference to a pure rvalue temporary (e.g., not
a class temporary), by creating a new temporary and copying the result
there. Fixes PR6024.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@108431 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/CGExpr.cpp b/lib/CodeGen/CGExpr.cpp
index 43bab9fece..94fb086b4c 100644
--- a/lib/CodeGen/CGExpr.cpp
+++ b/lib/CodeGen/CGExpr.cpp
@@ -1749,8 +1749,48 @@ CodeGenFunction::EmitConditionalOperatorLValue(const ConditionalOperator* E) {
 /// cast from scalar to union.
 LValue CodeGenFunction::EmitCastLValue(const CastExpr *E) {
   switch (E->getCastKind()) {
-  default:
+  case CastExpr::CK_ToVoid:
     return EmitUnsupportedLValue(E, "unexpected cast lvalue");
+   
+  case CastExpr::CK_NoOp:
+    if (E->getSubExpr()->getType()->isRecordType() ||
+        E->getSubExpr()->isLvalue(getContext()) == Expr::LV_Valid) {
+      LValue LV = EmitLValue(E->getSubExpr());
+      if (LV.isPropertyRef()) {
+        QualType QT = E->getSubExpr()->getType();
+        RValue RV = EmitLoadOfPropertyRefLValue(LV, QT);
+        assert(!RV.isScalar() && "EmitCastLValue - scalar cast of property ref");
+        llvm::Value *V = RV.getAggregateAddr();
+        return LValue::MakeAddr(V, MakeQualifiers(QT));
+      }
+      return LV;
+    }
+    // Fall through to synthesize a temporary.
+      
+  case CastExpr::CK_Unknown:
+  case CastExpr::CK_BitCast:
+  case CastExpr::CK_ArrayToPointerDecay:
+  case CastExpr::CK_FunctionToPointerDecay:
+  case CastExpr::CK_NullToMemberPointer:
+  case CastExpr::CK_IntegralToPointer:
+  case CastExpr::CK_PointerToIntegral:
+  case CastExpr::CK_VectorSplat:
+  case CastExpr::CK_IntegralCast:
+  case CastExpr::CK_IntegralToFloating:
+  case CastExpr::CK_FloatingToIntegral:
+  case CastExpr::CK_FloatingCast:
+  case CastExpr::CK_DerivedToBaseMemberPointer:
+  case CastExpr::CK_BaseToDerivedMemberPointer:
+  case CastExpr::CK_MemberPointerToBoolean:
+  case CastExpr::CK_AnyPointerToBlockPointerCast: {
+    // These casts only produce lvalues when we're binding a reference to a 
+    // temporary realized from a (converted) pure rvalue. Emit the expression
+    // as a value, copy it into a temporary, and return an lvalue referring to
+    // that temporary.
+    llvm::Value *V = CreateMemTemp(E->getType(), "ref.temp");
+    EmitAnyExprToMem(E, V, false, false);
+    return LValue::MakeAddr(V, MakeQualifiers(E->getType()));
+  }
 
   case CastExpr::CK_Dynamic: {
     LValue LV = EmitLValue(E->getSubExpr());
@@ -1760,17 +1800,6 @@ LValue CodeGenFunction::EmitCastLValue(const CastExpr *E) {
                             MakeQualifiers(E->getType()));
   }
 
-  case CastExpr::CK_NoOp: {
-    LValue LV = EmitLValue(E->getSubExpr());
-    if (LV.isPropertyRef()) {
-      QualType QT = E->getSubExpr()->getType();
-      RValue RV = EmitLoadOfPropertyRefLValue(LV, QT);
-      assert(!RV.isScalar() && "EmitCastLValue - scalar cast of property ref");
-      llvm::Value *V = RV.getAggregateAddr();
-      return LValue::MakeAddr(V, MakeQualifiers(QT));
-    }
-    return LV;
-  }
   case CastExpr::CK_ConstructorConversion:
   case CastExpr::CK_UserDefinedConversion:
   case CastExpr::CK_AnyPointerToObjCPointerCast:
@@ -1826,6 +1855,8 @@ LValue CodeGenFunction::EmitCastLValue(const CastExpr *E) {
     return LValue::MakeAddr(V, MakeQualifiers(E->getType()));
   }
   }
+  
+  llvm_unreachable("Unhandled lvalue cast kind?");
 }
 
 LValue CodeGenFunction::EmitNullInitializationLValue(
diff --git a/test/CodeGenCXX/reference-cast.cpp b/test/CodeGenCXX/reference-cast.cpp
new file mode 100644
index 0000000000..49409d7be1
--- /dev/null
+++ b/test/CodeGenCXX/reference-cast.cpp
@@ -0,0 +1,170 @@
+// RUN: %clang_cc1 -emit-llvm -triple x86_64-apple-darwin10 -o - %s | FileCheck %s
+
+// PR6024
+extern int i;
+
+// CHECK: define i32* @_Z16lvalue_noop_castv() nounwind
+const int &lvalue_noop_cast() {
+  if (i == 0)
+    // CHECK: store i32 17, i32*
+    return (const int&)17;
+  else if (i == 1)
+    // CHECK: store i32 17, i32*
+    return static_cast<const int&>(17);
+    // CHECK: store i32 17, i32*
+  return 17;
+}
+
+// CHECK: define i16* @_Z20lvalue_integral_castv() 
+const short &lvalue_integral_cast() {
+  if (i == 0)
+    // CHECK: store i16 17, i16*
+    return (const short&)17;
+  else if (i == 1)
+    // CHECK: store i16 17, i16*
+    return static_cast<const short&>(17);
+  // CHECK: store i16 17, i16*
+  return 17;
+}
+
+// CHECK: define i16* @_Z29lvalue_floating_integral_castv()
+const short &lvalue_floating_integral_cast() {
+  if (i == 0)
+    // CHECK: store i16 17, i16*
+    return (const short&)17.5;
+  else if (i == 1)
+    // CHECK: store i16 17, i16*
+    return static_cast<const short&>(17.5);
+  // CHECK: store i16 17, i16*
+  return 17.5;
+}
+
+// CHECK: define float* @_Z29lvalue_integral_floating_castv()
+const float &lvalue_integral_floating_cast() {
+  if (i == 0)
+    // CHECK: store float 1.700000e+01, float*
+    return (const float&)17;
+  else if (i == 1)
+    // CHECK: store float 1.700000e+01, float*
+    return static_cast<const float&>(17);
+  // CHECK: store float 1.700000e+01, float*
+  return 17;
+}
+
+// CHECK: define float* @_Z20lvalue_floating_castv()
+const float &lvalue_floating_cast() {
+  if (i == 0)
+    // CHECK: store float 1.700000e+01, float*
+    return (const float&)17.0;
+  else if (i == 1)
+    // CHECK: store float 1.700000e+01, float*
+    return static_cast<const float&>(17.0);
+  // CHECK: store float 1.700000e+01, float*
+  return 17.0;
+}
+
+int get_int();
+
+// CHECK: define i8* @_Z24lvalue_integer_bool_castv()
+const bool &lvalue_integer_bool_cast() {
+  if (i == 0)
+    // CHECK: call i32 @_Z7get_intv()
+    // CHECK: store i8
+    return (const bool&)get_int();
+  else if (i == 1)
+    // CHECK: call i32 @_Z7get_intv()
+    // CHECK: store i8
+    return static_cast<const bool&>(get_int());
+  // CHECK: call i32 @_Z7get_intv()
+  // CHECK: store i8
+  return get_int();
+}
+
+float get_float();
+
+// CHECK: define i8* @_Z25lvalue_floating_bool_castv()
+const bool &lvalue_floating_bool_cast() {
+  if (i == 0)
+    // CHECK: call float @_Z9get_floatv()
+    // CHECK: fcmp une float
+    // CHECK: store i8
+    return (const bool&)get_float();
+  else if (i == 1)
+    // CHECK: call float @_Z9get_floatv()
+    // CHECK: fcmp une float
+    // CHECK: store i8
+    return static_cast<const bool&>(get_float());
+  // CHECK: call float @_Z9get_floatv()
+  // CHECK: fcmp une float
+  // CHECK: store i8
+  return get_float();
+}
+
+struct X { };
+typedef int X::*pm;
+typedef int (X::*pmf)(int);
+
+pm get_pointer_to_member_data();
+pmf get_pointer_to_member_function();
+
+// CHECK: define i8* @_Z26lvalue_ptrmem_to_bool_castv()
+const bool &lvalue_ptrmem_to_bool_cast() {
+  if (i == 0)
+    // CHECK: call i64 @_Z26get_pointer_to_member_datav()
+    // CHECK: store i8
+    // CHECK: store i8*
+    return (const bool&)get_pointer_to_member_data();
+  else if (i == 1)
+    // CHECK: call i64 @_Z26get_pointer_to_member_datav()
+    // CHECK: store i8
+    // CHECK: store i8*
+    return static_cast<const bool&>(get_pointer_to_member_data());
+  // CHECK: call i64 @_Z26get_pointer_to_member_datav()
+  // CHECK: store i8
+  // CHECK: store i8*
+  return get_pointer_to_member_data();
+}
+
+// CHECK: define i8* @_Z27lvalue_ptrmem_to_bool_cast2v
+const bool &lvalue_ptrmem_to_bool_cast2() {
+  if (i == 0)
+    // CHECK: {{call.*_Z30get_pointer_to_member_functionv}}
+    // CHECK: store i8
+    // CHECK: store i8*
+    return (const bool&)get_pointer_to_member_function();
+  else if (i == 1)
+    // CHECK: {{call.*_Z30get_pointer_to_member_functionv}}
+    // CHECK: store i8
+    // CHECK: store i8*
+    return static_cast<const bool&>(get_pointer_to_member_function());
+  // CHECK: {{call.*_Z30get_pointer_to_member_functionv}}
+  // CHECK: store i8
+  // CHECK: store i8*
+  return get_pointer_to_member_function();
+}
+
+_Complex double get_complex_double();
+
+// CHECK: {{define.*_Z2f1v}}
+const _Complex float &f1() {
+  if (i == 0)
+    // CHECK: {{call.*_Z18get_complex_doublev}}
+    // CHECK: fptrunc
+    // CHECK: fptrunc
+    // CHECK: store float
+    // CHECK: store float
+    return (const _Complex float&)get_complex_double();
+  else if (i == 1)
+    // CHECK: {{call.*_Z18get_complex_doublev}}
+    // CHECK: fptrunc
+    // CHECK: fptrunc
+    // CHECK: store float
+    // CHECK: store float
+    return static_cast<const _Complex float&>(get_complex_double());
+  // CHECK: {{call.*_Z18get_complex_doublev}}
+  // CHECK: fptrunc
+  // CHECK: fptrunc
+  // CHECK: store float
+  // CHECK: store float
+  return get_complex_double();
+}