objc-arc: Perform null check on receiver before sending methods which

consume one or more of their arguments. If not done, this will cause a leak
as method will not consume the argument when receiver is null.
// rdar://10444474


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@149184 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 69 insertions, 1 deletions

diff --git a/lib/CodeGen/CodeGenFunction.h b/lib/CodeGen/CodeGenFunction.h
index e105f31f0f..ef81087c3f 100644
--- a/lib/CodeGen/CodeGenFunction.h
+++ b/lib/CodeGen/CodeGenFunction.h
@@ -2627,7 +2627,75 @@ template <> struct DominatingValue<RValue> {
   }
 };
 
+/// A helper class for performing the null-initialization of a return
+/// value.
+struct NullReturnState {
+  llvm::BasicBlock *NullBB;
+  llvm::BasicBlock *callBB;
+  NullReturnState() : NullBB(0), callBB(0) {}
+  
+  void init(CodeGenFunction &CGF, llvm::Value *receiver) {
+    // Make blocks for the null-init and call edges.
+    NullBB = CGF.createBasicBlock("msgSend.nullinit");
+    callBB = CGF.createBasicBlock("msgSend.call");
+    
+    // Check for a null receiver and, if there is one, jump to the
+    // null-init test.
+    llvm::Value *isNull = CGF.Builder.CreateIsNull(receiver);
+    CGF.Builder.CreateCondBr(isNull, NullBB, callBB);
+    
+    // Otherwise, start performing the call.
+    CGF.EmitBlock(callBB);
+  }
+  
+  RValue complete(CodeGenFunction &CGF, RValue result, QualType resultType) {
+    if (!NullBB) return result;
+    
+    llvm::Value *NullInitPtr = 0;
+    if (result.isScalar() && !resultType->isVoidType()) {
+      NullInitPtr = CGF.CreateTempAlloca(result.getScalarVal()->getType());
+      CGF.Builder.CreateStore(result.getScalarVal(), NullInitPtr);
+    }
+    // Finish the call path.
+    llvm::BasicBlock *contBB = CGF.createBasicBlock("msgSend.cont");
+    if (CGF.HaveInsertPoint()) CGF.Builder.CreateBr(contBB);
+    
+    // Emit the null-init block and perform the null-initialization there.
+    CGF.EmitBlock(NullBB);
+    if (result.isScalar()) {
+      if (NullInitPtr)
+        CGF.EmitNullInitialization(NullInitPtr, resultType);
+      // Jump to the continuation block.
+      CGF.EmitBlock(contBB);
+      return NullInitPtr ? RValue::get(CGF.Builder.CreateLoad(NullInitPtr))
+      : result;
+    }
+    
+    if (!resultType->isAnyComplexType()) {
+      assert(result.isAggregate() && "null init of non-aggregate result?");
+      CGF.EmitNullInitialization(result.getAggregateAddr(), resultType);
+      // Jump to the continuation block.
+      CGF.EmitBlock(contBB);
+      return result;
+    }
+    
+    // _Complex type
+    // FIXME. Now easy to handle any other scalar type whose result is returned
+    // in memory due to ABI limitations.
+    CGF.EmitBlock(contBB);
+    CodeGenFunction::ComplexPairTy CallCV = result.getComplexVal();
+    llvm::Type *MemberType = CallCV.first->getType();
+    llvm::Constant *ZeroCV = llvm::Constant::getNullValue(MemberType);
+    // Create phi instruction for scalar complex value.
+    llvm::PHINode *PHIReal = CGF.Builder.CreatePHI(MemberType, 2);
+    PHIReal->addIncoming(ZeroCV, NullBB);
+    PHIReal->addIncoming(CallCV.first, callBB);
+    llvm::PHINode *PHIImag = CGF.Builder.CreatePHI(MemberType, 2);
+    PHIImag->addIncoming(ZeroCV, NullBB);
+    PHIImag->addIncoming(CallCV.second, callBB);
+    return RValue::getComplex(PHIReal, PHIImag);
+  }
+};
 }  // end namespace CodeGen
 }  // end namespace clang
-
 #endif