[llvm-dev] Error Calling eraseFromParent()

[mayuyu.io via llvm-dev]

Hmmmm that’s strange. Do you get an assert when you build LLVM with this code in Debug Mode or is it simply null pointer dereference? 
On a side note, usually when doing transforms similar to yours I use IRBuilder’s CreateXXX followed by a ReplaceInstWithInst which works perfectly fine for me.

Zhang

> 在 2018年8月9日，00:29，Ahmad Nouralizadeh <ahmadnouralizadeh at gmail.com> 写道：
> 
> Hi. Thanks. I changed the code but the problem exists. This is my new code which is again very simple:
> ...
> bool runOnFunction(Function &F) override {
> 
> vector<Instruction *> dels;
> dels.clear();
> 
> for (inst_iterator It = inst_begin(&F), Ie = inst_end(&F); It != Ie;) {
> 	Instruction *I = &*(It++);
> 
> 	if (auto* op = dyn_cast<BinaryOperator>(I)) {
> 		IRBuilder<NoFolder> builder(op);
> 
> 		Value* lhs = op->getOperand(0);
> 		Value* rhs = op->getOperand(1);
> 		Value* mul = builder.CreateMul(lhs, rhs);
> 
> 		for (auto& U : op->uses()) {
> 		  User* user = U.getUser();
> 		  user->setOperand(U.getOperandNo(), mul);
> 		}
> 		//I->eraseFromParent();
> 		dels.push_back(I);
> 	}
> }	
> 
> for (auto &I : dels) {
> 	I->eraseFromParent();
> }
> ...
> 
>> On Wed, Aug 8, 2018 at 6:16 PM, mayuyu.io <admin at mayuyu.io> wrote:
>> Hi:
>> As stated in the documentation you shouldn’t modify it while iterating as this invalidates the iterator. Try save the pointers to a vector outside your loop and perform erasing in a new loop following your current one.
>> 
>> Zhang
>> 
>>> 在 2018年8月8日，07:54，Ahmad Nouralizadeh via llvm-dev <llvm-dev at lists.llvm.org> 写道：
>>> 
>>> Thanks Bjorn! But The problem is still there.
>>> 
>>>> On Wed, Aug 8, 2018 at 2:04 AM, Björn Pettersson A <bjorn.a.pettersson at ericsson.com> wrote:
>>>> It looks quite dangerous to erase the instruction I inside the loop when iterating over all instructions in the function.
>>>> I guess it depends on how the range based iterator is implemented if that works or not.
>>>> 
>>>> I think that you, for example, can change the range based iteration
>>>> 
>>>>    for (auto &I : instructions(F))
>>>> 
>>>> into something like this
>>>> 
>>>>    for (inst_iterator It = inst_begin(&F), Ie = inst_end(&F); It != Ie;) {
>>>>       Instruction *I = &*(It++);
>>>>       ...
>>>>     }
>>>> 
>>>> That will make sure that you step the iterator before modifying the data structure you iterate over.
>>>> 
>>>> Regards,
>>>> Björn
>>>> ________________________________________
>>>> From: llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of Ahmad Nouralizadeh via llvm-dev <llvm-dev at lists.llvm.org>
>>>> Sent: Tuesday, August 7, 2018 22:26
>>>> To: paul.robinson at sony.com
>>>> Cc: llvm-dev at lists.llvm.org
>>>> Subject: Re: [llvm-dev] Error Calling eraseFromParent()
>>>> 
>>>> The code is really simple. But I can not the reason for the segmentation fault. I only know that the eraseFromParent() function leads to it. The whole code is:
>>>> ...
>>>> bool runOnFunction(Function &F) override {
>>>> 
>>>> for (auto &I : instructions(F)) {
>>>> 
>>>> if (auto* op = dyn_cast<BinaryOperator>(&I)) {
>>>> IRBuilder<> builder(op);
>>>> 
>>>> Value* lhs = op->getOperand(0);
>>>> Value* rhs = op->getOperand(1);
>>>> Value* mul = builder.CreateMul(lhs, rhs);
>>>> 
>>>> for (auto& U : op->uses()) {
>>>>   User* user = U.getUser();
>>>>   user->setOperand(U.getOperandNo(), mul);
>>>> }
>>>> 
>>>> I.eraseFromParent();
>>>>     }
>>>> 
>>>> }
>>>> ...
>>>> And I think that the code worked well with LLVM-3.6.0 that I tested one year ago. Now, I use LLVM-6.0.0.
>>>> Regards.
>>> 
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20180809/164021c0/attachment.html>