From fc1e6c79bbfe0e9a58bb792996d51f42e36e3d6a Mon Sep 17 00:00:00 2001
From: John McCall <rjmccall@apple.com>
Date: Sat, 18 Sep 2010 00:58:34 +0000
Subject: [PATCH] Fix a bug with binding l-values to elided temporaries, and
 leave a couple helpful asserts behind.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@114250 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/CGExpr.cpp          | 10 +++++++---
 lib/CodeGen/CGExprCXX.cpp       |  8 +++++---
 test/CodeGenCXX/temporaries.cpp | 19 ++++++++++++++++++-
 3 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/lib/CodeGen/CGExpr.cpp b/lib/CodeGen/CGExpr.cpp
index 9c1a3cf249..924ca3ec4b 100644
--- a/lib/CodeGen/CGExpr.cpp
+++ b/lib/CodeGen/CGExpr.cpp
@@ -1964,6 +1964,8 @@ LValue CodeGenFunction::EmitVAArgExprLValue(const VAArgExpr *E) {
 }
 
 LValue CodeGenFunction::EmitCXXConstructLValue(const CXXConstructExpr *E) {
+  assert(E->getType()->getAsCXXRecordDecl()->hasTrivialDestructor()
+         && "binding l-value to type which needs a temporary");
   AggValueSlot Slot = CreateAggTemp(E->getType(), "tmp");
   EmitCXXConstructExpr(E, Slot);
   return MakeAddrLValue(Slot.getAddr(), E->getType());
@@ -1976,9 +1978,11 @@ CodeGenFunction::EmitCXXTypeidLValue(const CXXTypeidExpr *E) {
 
 LValue
 CodeGenFunction::EmitCXXBindTemporaryLValue(const CXXBindTemporaryExpr *E) {
-  LValue LV = EmitLValue(E->getSubExpr());
-  EmitCXXTemporary(E->getTemporary(), LV.getAddress());
-  return LV;
+  AggValueSlot Slot = CreateAggTemp(E->getType(), "temp.lvalue");
+  Slot.setLifetimeExternallyManaged();
+  EmitAggExpr(E->getSubExpr(), Slot);
+  EmitCXXTemporary(E->getTemporary(), Slot.getAddr());
+  return MakeAddrLValue(Slot.getAddr(), E->getType());
 }
 
 LValue CodeGenFunction::EmitObjCMessageExprLValue(const ObjCMessageExpr *E) {
diff --git a/lib/CodeGen/CGExprCXX.cpp b/lib/CodeGen/CGExprCXX.cpp
index 4dbfa7ee4f..aadceff8be 100644
--- a/lib/CodeGen/CGExprCXX.cpp
+++ b/lib/CodeGen/CGExprCXX.cpp
@@ -280,10 +280,12 @@ CodeGenFunction::EmitCXXConstructExpr(const CXXConstructExpr *E,
   if (CD->isTrivial() && CD->isDefaultConstructor())
     return;
   
-  // Code gen optimization to eliminate copy constructor and return
-  // its first argument instead, if in fact that argument is a temporary 
-  // object.
+  // Elide the constructor if we're constructing from a temporary.
+  // The temporary check is required because Sema sets this on NRVO
+  // returns.
   if (getContext().getLangOptions().ElideConstructors && E->isElidable()) {
+    assert(getContext().hasSameUnqualifiedType(E->getType(),
+                                               E->getArg(0)->getType()));
     if (E->getArg(0)->isTemporaryObject(getContext(), CD->getParent())) {
       EmitAggExpr(E->getArg(0), Dest);
       return;
diff --git a/test/CodeGenCXX/temporaries.cpp b/test/CodeGenCXX/temporaries.cpp
index 7996ed656d..3bf1dbd9f4 100644
--- a/test/CodeGenCXX/temporaries.cpp
+++ b/test/CodeGenCXX/temporaries.cpp
@@ -340,7 +340,11 @@ namespace PR7556 {
 }
 
 namespace Elision {
-  struct A { A(); A(const A &); ~A(); void *p; };
+  struct A {
+    A(); A(const A &); ~A();
+    void *p;
+    void foo() const;
+  };
 
   void foo();
   A fooA();
@@ -475,4 +479,17 @@ namespace Elision {
 
     // CHECK:      call void @_ZN7Elision1AD1Ev([[A]]* [[X]])
   }
+
+  // Reduced from webkit.
+  // CHECK: define void @_ZN7Elision5test6EPKNS_1CE([[C:%.*]]*
+  struct C { operator A() const; };
+  void test6(const C *x) {
+    // CHECK:      [[T0:%.*]] = alloca [[A]], align 8
+    // CHECK:      [[X:%.*]] = load [[C]]** {{%.*}}, align 8
+    // CHECK-NEXT: call void @_ZNK7Elision1CcvNS_1AEEv([[A]]* sret [[T0]], [[C]]* [[X]])
+    // CHECK-NEXT: call void @_ZNK7Elision1A3fooEv([[A]]* [[T0]])
+    // CHECK-NEXT: call void @_ZN7Elision1AD1Ev([[A]]* [[T0]])
+    // CHECK-NEXT: ret void
+    A(*x).foo();
+  }
 }