[llvm-dev] Creating/Deleting a new instruction from LLVM IR
Ansar K.A. via llvm-dev
llvm-dev at lists.llvm.org
Thu Nov 26 21:42:27 PST 2015
I got it.
Thank you.
On 26 November 2015 at 11:16, Mehdi Amini <mehdi.amini at apple.com> wrote:
>
> On Nov 25, 2015, at 9:42 PM, Ansar K.A. <k.abuansar at gmail.com> wrote:
>
> Hi,
>
> What I am trying to do is to check duplicate arithmetic instructions, if
> found any, I want to delete that duplicate instruction and needed to add a *Store
> *Instruction.
>
> Code:
> Instruction* temp_Ins;
> for (Function::iterator b = F.begin(), be = F.end(); b != be; ++b)
> {
> for (BasicBlock::iterator i = b->begin(), ie = b->end(); i !=
> ie; ++i) {
>
> switch(curr_Ins->getOpcode()){
>
> case Instruction::Add: {
> // Here i am keeping expression and
> its address to a *Map. *Eg: *mymap[a+b]=i*
> // If 'a+b' is already in the list
> then i am trying to delete that new duplicate instruction from LLVM IR.
> // following is the code i wrote for
> deleting duplicate *add *instruction:
> temp_Ins = cast<Instruction>(i);
> temp_Ins->eraseFromParent();
> }
> }
> }
> }
>
> What I am doing wrong here ?
>
>
> This is what I suggested in my previous email: this is an iterator
> invalidation issue.
> You are iterating over a linked-list and you are removing the current node
> from the list and trying to increment the iterator afterward, but it is no
> longer part of the list at this point.
> This is more a C++ question and not LLVM related at this point: you need
> to move the increment of the iterator at the beginning of the loop body,
> just after getting the current instruction.
>
> —
> Mehdi
>
>
>
>
> - Ansar K.A.
>
> On 26 November 2015 at 09:22, Mehdi Amini <mehdi.amini at apple.com> wrote:
>
>> Hi,
>>
>> On Nov 25, 2015, at 7:05 PM, Ansar K.A. via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>> Hi,
>>
>> I was trying to create a new *Store* instruction and inserting it to
>> LLVM IR (.ll) file. I found the following constructor in LLVM Manual:
>>
>> StoreInst::StoreInst
>> <http://llvm.org/docs/doxygen/html/classllvm_1_1StoreInst.html#aa2a72f9a51b317f5b4ab8695adf59025>
>> (Value <http://llvm.org/docs/doxygen/html/classllvm_1_1Value.html> * Val,
>> Value <http://llvm.org/docs/doxygen/html/classllvm_1_1Value.html> * Ptr,
>> Instruction
>> <http://llvm.org/docs/doxygen/html/classllvm_1_1Instruction.html> *
>> InsertBefore )
>>
>> I thought of using this. I don't know the meaning of the constructors
>> arguments. What all values should be passed for creating a new *Store *Instruction
>> (with an *example) *?
>>
>>
>> How to insert this to LLVM IR? ( I saw the code snippet in LLVM
>> Programming manual, I couldn't understand it. Any examples on doing the
>> same? )
>>
>>
>>
>> - Val is the value you want to store.
>> - Ptr is the location where you want to store the value Val.
>> - InsertBefore is an optional pointer to an existing instruction, if it
>> is provided the newly created instruction will be just before the provided
>> one.
>>
>> Also you may want to use the IRBuilder in general to create IR, you may
>> want to follow the Kaleidoscope tutorial at least once (Creating a Store is
>> done chapter 7: http://llvm.org/docs/tutorial/LangImpl7.html )
>>
>>
>> I tried to delete an instruction using:
>>
>> i->eraseFromParent();
>>
>>
>>
>> From the trace it does not seem that this call is leading to the assert.
>> You’re not giving enough information about what you’re doing here. It could
>> be some iterator invalidation for example.
>>
>> —
>> Mehdi
>>
>>
>>
>>
>>
>>
>> But it throws the following error/exception:
>>
>> *opt -load /home/mtech2/Documents/llvm/build/Debug+Asserts/lib/CSE.so
>> -CSE <test.ll> /dev/null*
>> *opt: /home/mtech2/Documents/llvm/llvm/include/llvm/Support/Casting.h:81:
>> static bool llvm::isa_impl_cl<To, From*>::doit(const From*) [with To =
>> llvm::Instruction; From = llvm::Instruction]: Assertion `Val && "isa<> used
>> on a null pointer"' failed.*
>> *#0 0x29635a5 llvm::sys::PrintStackTrace(llvm::raw_ostream&)
>> /home/mtech2/Documents/llvm/llvm/lib/Support/Unix/Signals.inc:405:0*
>> *#1 0x29638ba PrintStackTraceSignalHandler(void*)
>> /home/mtech2/Documents/llvm/llvm/lib/Support/Unix/Signals.inc:463:0*
>> *#2 0x2961eb9 llvm::sys::RunSignalHandlers()
>> /home/mtech2/Documents/llvm/llvm/lib/Support/Signals.cpp:34:0*
>> *#3 0x29623b1 SignalHandler(int)
>> /home/mtech2/Documents/llvm/llvm/lib/Support/Unix/Signals.inc:211:0*
>> *#4 0x7f190977a340 __restore_rt
>> (/lib/x86_64-linux-gnu/libpthread.so.0+0x10340)*
>> *#5 0x7f1908715cc9 gsignal
>> /build/buildd/eglibc-2.19/signal/../nptl/sysdeps/unix/sysv/linux/raise.c:56:0*
>> *#6 0x7f19087190d8 abort /build/buildd/eglibc-2.19/stdlib/abort.c:91:0*
>> *#7 0x7f190870eb86 __assert_fail_base
>> /build/buildd/eglibc-2.19/assert/assert.c:92:0*
>> *#8 0x7f190870ec32 (/lib/x86_64-linux-gnu/libc.so.6+0x2fc32)*
>> *#9 0x7f19084d9970 llvm::isa_impl_cl<llvm::Instruction,
>> llvm::Instruction*>::doit(llvm::Instruction const*)
>> /home/mtech2/Documents/llvm/llvm/include/llvm/Support/Casting.h:82:0*
>> *#10 0x7f19084d9450 llvm::isa_impl_wrap<llvm::Instruction,
>> llvm::Instruction*, llvm::Instruction*>::doit(llvm::Instruction* const&)
>> /home/mtech2/Documents/llvm/llvm/include/llvm/Support/Casting.h:123:0*
>> *#11 0x7f19084d89e2 llvm::isa_impl_wrap<llvm::Instruction,
>> llvm::ilist_iterator<llvm::Instruction> const,
>> llvm::Instruction*>::doit(llvm::ilist_iterator<llvm::Instruction> const&)
>> /home/mtech2/Documents/llvm/llvm/include/llvm/Support/Casting.h:115:0*
>> *#12 0x7f19084d8371 bool llvm::isa<llvm::Instruction,
>> llvm::ilist_iterator<llvm::Instruction>
>> >(llvm::ilist_iterator<llvm::Instruction> const&)
>> /home/mtech2/Documents/llvm/llvm/include/llvm/Support/Casting.h:135:0*
>> *#13 0x7f19084d7ba1 llvm::cast_retty<llvm::Instruction,
>> llvm::ilist_iterator<llvm::Instruction> >::ret_type
>> llvm::cast<llvm::Instruction, llvm::ilist_iterator<llvm::Instruction>
>> >(llvm::ilist_iterator<llvm::Instruction>&)
>> /home/mtech2/Documents/llvm/llvm/include/llvm/Support/Casting.h:230:0*
>> *#14 0x7f19084d73fd (anonymous
>> namespace)::CSE::runOnFunction(llvm::Function&)
>> /home/mtech2/Documents/llvm/llvm/lib/Transforms/CSE/CSE.cpp:48:0*
>> *#15 0x288fd1c llvm::FPPassManager::runOnFunction(llvm::Function&)
>> /home/mtech2/Documents/llvm/llvm/lib/IR/LegacyPassManager.cpp:1528:0*
>> *#16 0x288feaf llvm::FPPassManager::runOnModule(llvm::Module&)
>> /home/mtech2/Documents/llvm/llvm/lib/IR/LegacyPassManager.cpp:1549:0*
>> *#17 0x289024a (anonymous
>> namespace)::MPPassManager::runOnModule(llvm::Module&)
>> /home/mtech2/Documents/llvm/llvm/lib/IR/LegacyPassManager.cpp:1605:0*
>> *#18 0x28909bb llvm::legacy::PassManagerImpl::run(llvm::Module&)
>> /home/mtech2/Documents/llvm/llvm/lib/IR/LegacyPassManager.cpp:1708:0*
>> *#19 0x2890bfb llvm::legacy::PassManager::run(llvm::Module&)
>> /home/mtech2/Documents/llvm/llvm/lib/IR/LegacyPassManager.cpp:1740:0*
>> *#20 0xee3bd2 main
>> /home/mtech2/Documents/llvm/llvm/tools/opt/opt.cpp:602:0*
>> *#21 0x7f1908700ec5 __libc_start_main
>> /build/buildd/eglibc-2.19/csu/libc-start.c:321:0*
>> *#22 0xec1739 _start
>> (/home/mtech2/Documents/llvm/build/Debug+Asserts/bin/opt+0xec1739)*
>> *Stack dump:*
>> *0. Program arguments: opt -load
>> /home/mtech2/Documents/llvm/build/Debug+Asserts/lib/CSE.so -CSE *
>> *1. Running pass 'Function Pass Manager' on module '<stdin>'.*
>> *2. Running pass 'Print Instructions' on function '@main'*
>> *Aborted (core dumped)*
>>
>> Any help will be appreciated.
>>
>>
>> - Ansar K.A.
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>>
>>
>
>
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