llvm dev - Sep 2011 - [LLVMdev] ICmpInst example?

I'm trying to come up with a simple example of using ICmpInst in a
Pass. On each of the branches(true, false) I'd like to call a separate
function and then resume(to the code that was already there).

In this example i is a inst_iterator to Instruction the Pass is
currently on. Now it segfaults opt before I can even get a dump() on
it. Does anyone see what I am doing wrong?

		BasicBlock *bb = i->getParent();
		Instruction *j = bb->end();
		BasicBlock *bb_after = i->getParent()->splitBasicBlock(&*i);
		bb->getTerminator()->eraseFromParent();

		ICmpInst *test = new ICmpInst(j, CmpInst::ICMP_EQ, shadow, val,
"Shadow check");
		
		BasicBlock *trueBlock = BasicBlock::Create(M.getContext(), "Shadow
Check Block: TRUE", &F);
		CallInst::Create(qv_true, "", trueBlock);
		BranchInst::Create(bb_after, trueBlock);
		
		BasicBlock *falseBlock = BasicBlock::Create(M.getContext(), "Shadow
Check Block: FALSE", &F);
		CallInst::Create(qv_false, "", falseBlock);
		BranchInst::Create(bb_after, falseBlock);
		
		BranchInst::Create(trueBlock, falseBlock, test, j);

On Tue, Sep 27, 2011 at 7:28 PM, ret val <retval386 at gmail.com>
wrote:
> I'm trying to come up with a simple example of using ICmpInst in a
> Pass. On each of the branches(true, false) I'd like to call a separate
> function and then resume(to the code that was already there).
>
> In this example i is a inst_iterator to Instruction the Pass is
> currently on. Now it segfaults opt before I can even get a dump() on
> it. Does anyone see what I am doing wrong?
>
>                BasicBlock *bb = i->getParent();
>                Instruction *j = bb->end();
Your initialization of "j" isn't valid: bb->end() doesn't
point at an
Instruction.

-Eli

On 9/27/11 10:00 PM, Eli Friedman wrote:
> On Tue, Sep 27, 2011 at 7:28 PM, ret val<retval386 at gmail.com> 
wrote:
>> I'm trying to come up with a simple example of using ICmpInst in a
>> Pass. On each of the branches(true, false) I'd like to call a
separate
>> function and then resume(to the code that was already there).
>>
>> In this example i is a inst_iterator to Instruction the Pass is
>> currently on. Now it segfaults opt before I can even get a dump() on
>> it. Does anyone see what I am doing wrong?
>>
>>                 BasicBlock *bb = i->getParent();
>>                 Instruction *j = bb->end();
> Your initialization of "j" isn't valid: bb->end()
doesn't point at an
> Instruction.
To add to this, if you want to get the last instruction in a basic 
block, just use BasicBlock::getTerminator().  All basic blocks must have 
a terminator instruction as the last instruction.

-- John T.
>
> -Eli
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

Perhaps try j->back();

Joe

Sent from my iPad

On Sep 27, 2011, at 11:00 PM, Eli Friedman <eli.friedman at gmail.com>
wrote:
> On Tue, Sep 27, 2011 at 7:28 PM, ret val <retval386 at gmail.com>
wrote:
>> I'm trying to come up with a simple example of using ICmpInst in a
>> Pass. On each of the branches(true, false) I'd like to call a
separate
>> function and then resume(to the code that was already there).
>> 
>> In this example i is a inst_iterator to Instruction the Pass is
>> currently on. Now it segfaults opt before I can even get a dump() on
>> it. Does anyone see what I am doing wrong?
>> 
>>                BasicBlock *bb = i->getParent();
>>                Instruction *j = bb->end();
> 
> Your initialization of "j" isn't valid: bb->end()
doesn't point at an
> Instruction.
> 
> -Eli
> 
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev