[cfe-commits] r102430 - /cfe/trunk/lib/CodeGen/CGObjCGNU.cpp
David Chisnall
csdavec at swan.ac.uk
Tue Apr 27 08:08:48 PDT 2010
Author: theraven
Date: Tue Apr 27 10:08:48 2010
New Revision: 102430
URL: http://llvm.org/viewvc/llvm-project?rev=102430&view=rev
Log:
Ensure return from a message to nil is always 0 (GNU runtime).
This works around stack corruption / crashes resulting from PR6944, and also
works around people who expect 'what works on my machine' to work everywhere
(GCC crashes in a number of cases on SPARC that should now work correctly with
clang).
Modified:
cfe/trunk/lib/CodeGen/CGObjCGNU.cpp
Modified: cfe/trunk/lib/CodeGen/CGObjCGNU.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGObjCGNU.cpp?rev=102430&r1=102429&r2=102430&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGObjCGNU.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGObjCGNU.cpp Tue Apr 27 10:08:48 2010
@@ -548,6 +548,7 @@
bool IsClassMessage,
const CallArgList &CallArgs,
const ObjCMethodDecl *Method) {
+ // Strip out message sends to retain / release in GC mode
if (CGM.getLangOptions().getGCMode() != LangOptions::NonGC) {
if (Sel == RetainSel || Sel == AutoreleaseSel) {
return RValue::get(Receiver);
@@ -556,7 +557,38 @@
return RValue::get(0);
}
}
+
CGBuilderTy &Builder = CGF.Builder;
+
+ // If the return type is something that goes in an integer register, the
+ // runtime will handle 0 returns. For other cases, we fill in the 0 value
+ // ourselves.
+ //
+ // The language spec says the result of this kind of message send is
+ // undefined, but lots of people seem to have forgotten to read that
+ // paragraph and insist on sending messages to nil that have structure
+ // returns. With GCC, this generates a random return value (whatever happens
+ // to be on the stack / in those registers at the time) on most platforms,
+ // and generates a SegV on SPARC. With LLVM it corrupts the stack.
+ bool isPointerSizedReturn = false;
+ if (ResultType->isAnyPointerType() || ResultType->isIntegralType())
+ isPointerSizedReturn = true;
+
+ llvm::BasicBlock *startBB = 0;
+ llvm::BasicBlock *messageBB = 0;
+ llvm::BasicBlock *contiueBB = 0;
+
+ if (!isPointerSizedReturn) {
+ startBB = Builder.GetInsertBlock();
+ messageBB = CGF.createBasicBlock("msgSend");
+ contiueBB = CGF.createBasicBlock("continue");
+
+ llvm::Value *isNil = Builder.CreateICmpEQ(Receiver,
+ llvm::Constant::getNullValue(Receiver->getType()));
+ Builder.CreateCondBr(isNil, contiueBB, messageBB);
+ CGF.EmitBlock(messageBB);
+ }
+
IdTy = cast<llvm::PointerType>(CGM.getTypes().ConvertType(ASTIdTy));
llvm::Value *cmd;
if (Method)
@@ -631,7 +663,41 @@
imp = Builder.CreateCall2(lookupFunction, Receiver, cmd);
}
- return CGF.EmitCall(FnInfo, imp, ReturnValueSlot(), ActualArgs);
+ RValue msgRet =
+ CGF.EmitCall(FnInfo, imp, ReturnValueSlot(), ActualArgs);
+
+ if (!isPointerSizedReturn) {
+ CGF.EmitBlock(contiueBB);
+ if (msgRet.isScalar()) {
+ llvm::Value *v = msgRet.getScalarVal();
+ llvm::PHINode *phi = Builder.CreatePHI(v->getType());
+ phi->addIncoming(v, messageBB);
+ phi->addIncoming(llvm::Constant::getNullValue(v->getType()), startBB);
+ msgRet = RValue::get(phi);
+ } else if (msgRet.isAggregate()) {
+ llvm::Value *v = msgRet.getAggregateAddr();
+ llvm::PHINode *phi = Builder.CreatePHI(v->getType());
+ const llvm::PointerType *RetTy = cast<llvm::PointerType>(v->getType());
+ llvm::AllocaInst *NullVal = CGF.CreateTempAlloca(RetTy, "null");
+ CGF.InitTempAlloca(NullVal,
+ llvm::Constant::getNullValue(RetTy->getElementType()));
+ phi->addIncoming(v, messageBB);
+ phi->addIncoming(NullVal, startBB);
+ msgRet = RValue::getAggregate(phi);
+ } else /* isComplex() */ {
+ std::pair<llvm::Value*,llvm::Value*> v = msgRet.getComplexVal();
+ llvm::PHINode *phi = Builder.CreatePHI(v.first->getType());
+ phi->addIncoming(v.first, messageBB);
+ phi->addIncoming(llvm::Constant::getNullValue(v.first->getType()),
+ startBB);
+ llvm::PHINode *phi2 = Builder.CreatePHI(v.second->getType());
+ phi2->addIncoming(v.second, messageBB);
+ phi2->addIncoming(llvm::Constant::getNullValue(v.second->getType()),
+ startBB);
+ msgRet = RValue::getComplex(phi, phi2);
+ }
+ }
+ return msgRet;
}
/// Generates a MethodList. Used in construction of a objc_class and
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