[CodeGen][ObjC] Do not call objc_storeStrong when initializing a

constexpr variable.

When compiling a constexpr NSString initialized with an objective-c
string literal, CodeGen emits objc_storeStrong on an uninitialized
alloca, which causes a crash.

This patch folds the code in EmitScalarInit into EmitStoreThroughLValue
and fixes the crash by calling objc_retain on the string instead of
using objc_storeStrong.

rdar://problem/28562009

Differential Revision: https://reviews.llvm.org/D25547


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@284516 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/CGDecl.cpp

@@ -774,37 +774,6 @@ void CodeGenFunction::EmitScalarInit(const Expr *init, const ValueDecl *D,
   EmitStoreOfScalar(value, lvalue, /* isInitialization */ true);
 }
 
-/// EmitScalarInit - Initialize the given lvalue with the given object.
-void CodeGenFunction::EmitScalarInit(llvm::Value *init, LValue lvalue) {
-  Qualifiers::ObjCLifetime lifetime = lvalue.getObjCLifetime();
-  if (!lifetime)
-    return EmitStoreThroughLValue(RValue::get(init), lvalue, true);
-
-  switch (lifetime) {
-  case Qualifiers::OCL_None:
-    llvm_unreachable("present but none");
-
-  case Qualifiers::OCL_ExplicitNone:
-    // nothing to do
-    break;
-
-  case Qualifiers::OCL_Strong:
-    init = EmitARCRetain(lvalue.getType(), init);
-    break;
-
-  case Qualifiers::OCL_Weak:
-    // Initialize and then skip the primitive store.
-    EmitARCInitWeak(lvalue.getAddress(), init);
-    return;
-
-  case Qualifiers::OCL_Autoreleasing:
-    init = EmitARCRetainAutorelease(lvalue.getType(), init);
-    break;
-  }
-
-  EmitStoreOfScalar(init, lvalue, /* isInitialization */ true);
-}
-
 /// canEmitInitWithFewStoresAfterMemset - Decide whether we can emit the
 /// non-zero parts of the specified initializer with equal or fewer than
 /// NumStores scalar stores.

lib/CodeGen/CGExpr.cpp

@@ -1629,11 +1629,19 @@ void CodeGenFunction::EmitStoreThroughLValue(RValue Src, LValue Dst,
       break;
 
     case Qualifiers::OCL_Strong:
+      if (isInit) {
+        Src = RValue::get(EmitARCRetain(Dst.getType(), Src.getScalarVal()));
+        break;
+      }
       EmitARCStoreStrong(Dst, Src.getScalarVal(), /*ignore*/ true);
       return;
 
     case Qualifiers::OCL_Weak:
-      EmitARCStoreWeak(Dst.getAddress(), Src.getScalarVal(), /*ignore*/ true);
+      if (isInit)
+        // Initialize and then skip the primitive store.
+        EmitARCInitWeak(Dst.getAddress(), Src.getScalarVal());
+      else
+        EmitARCStoreWeak(Dst.getAddress(), Src.getScalarVal(), /*ignore*/ true);
       return;
 
     case Qualifiers::OCL_Autoreleasing:

lib/CodeGen/CGObjC.cpp

@@ -1662,7 +1662,8 @@ void CodeGenFunction::EmitObjCForCollectionStmt(const ObjCForCollectionStmt &S){
     elementLValue = EmitLValue(cast<Expr>(S.getElement()));
     EmitStoreThroughLValue(RValue::get(CurrentItem), elementLValue);
   } else {
-    EmitScalarInit(CurrentItem, elementLValue);
+    EmitStoreThroughLValue(RValue::get(CurrentItem), elementLValue,
+                           /*isInit*/ true);
   }
 
   // If we do have an element variable, this assignment is the end of

lib/CodeGen/CGStmtOpenMP.cpp

@@ -188,7 +188,7 @@ static Address castValueFromUintptr(CodeGenFunction &CGF, QualType DstType,
     auto *RefVal = TmpAddr.getPointer();
     TmpAddr = CGF.CreateMemTemp(RefType, Twine(Name) + ".ref");
     auto TmpLVal = CGF.MakeAddrLValue(TmpAddr, RefType);
-    CGF.EmitScalarInit(RefVal, TmpLVal);
+    CGF.EmitStoreThroughLValue(RValue::get(RefVal), TmpLVal, /*isInit*/ true);
   }
 
   return TmpAddr;
@@ -2192,7 +2192,7 @@ static LValue createSectionLVal(CodeGenFunction &CGF, QualType Ty,
                                 llvm::Value *Init = nullptr) {
   auto LVal = CGF.MakeAddrLValue(CGF.CreateMemTemp(Ty, Name), Ty);
   if (Init)
-    CGF.EmitScalarInit(Init, LVal);
+    CGF.EmitStoreThroughLValue(RValue::get(Init), LVal, /*isInit*/ true);
   return LVal;
 }
 

lib/CodeGen/CodeGenFunction.h

@@ -2119,7 +2119,6 @@ public:
 
   void EmitScalarInit(const Expr *init, const ValueDecl *D, LValue lvalue,
                       bool capturedByInit);
-  void EmitScalarInit(llvm::Value *init, LValue lvalue);
 
   typedef void SpecialInitFn(CodeGenFunction &Init, const VarDecl &D,
                              llvm::Value *Address);

test/CodeGenObjCXX/arc-constexpr.mm

@@ -0,0 +1,18 @@
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -emit-llvm -fobjc-arc -o - -std=c++11 %s | FileCheck %s
+
+// CHECK: %[[TYPE:[a-z0-9]+]] = type opaque
+// CHECK: @[[CFSTRING:[a-z0-9_]+]] = private global %struct.__NSConstantString_tag
+
+// CHECK: define void @_Z5test1v
+// CHECK:   %[[ALLOCA:[A-Z]+]] = alloca %[[TYPE]]*
+// CHECK:   %[[V0:[0-9]+]] = call i8* @objc_retain(i8* bitcast (%struct.__NSConstantString_tag* @[[CFSTRING]]
+// CHECK:   %[[V1:[0-9]+]] = bitcast i8* %[[V0]] to %[[TYPE]]*
+// CHECK:   store %[[TYPE]]* %[[V1]], %[[TYPE]]** %[[ALLOCA]]
+// CHECK:   %[[V2:[0-9]+]] = bitcast %[[TYPE]]** %[[ALLOCA]]
+// CHECK:   call void @objc_storeStrong(i8** %[[V2]], i8* null)
+
+@class NSString;
+
+void test1() {
+  constexpr NSString *S = @"abc";
+}