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Óscar Fuentes

2011-Nov-03 08:44 UTC

[LLVMdev] LLVM problem, please do not ignore

Hello John,

John Criswell <criswell at illinois.edu> writes:

[snip]
> By the way, it looks like you don't have a build with assertions
> enabled.  I recommend compiling with
>
> gmake ENABLE_OPTIMIZED=0 DISABLE_ASSERTIONS=1
Shouldn't the above be DISABLE_ASSERTIONS=0 ? (which means
DISABLE_ASSERTIONS=No, introducing the dreaded double negation which
causes so much confusion on some people.)

BTW, Debug+Asserts is the default mode in the configure&make build.

Arshak Nazaryan

2011-Nov-03 10:55 UTC

head link

[LLVMdev] LLVM problem, please do not ignore

Dear sir or madam,

I am a 4-th year student at Yerevan State University, Armenia; and I am
studying LLVM in order to write my Bachelor thesis.
I am trying to write an llvm pass that just removes all "Add" commands
and
gives some statstics.
Nevertheless, I get this segmentation fault:

................some rows about functions, that are not changed by my pass.
The errors occurs after it has modified a "@_Z3addii" function.
store i32 %b.0, i32* %4  and the type is ddddbbm 28
  %5 = load i32* %a_addr, align 4  and the type is ddddbbm 27
  %6 = load i32* %b_addr, align 4  and the type is ddddbbm 27
  %7 = add nsw i32 %5, %6  and the type is ddddbbm 8
  store i32 %7, i32* %0, align 4  and the type is ddddbbm 28
  %7 = add nsw i32 %5, %6   is erased, ba!
  %7 = load i32* %0, align 4  and the type is ddddbbm 27
  store i32 %7, i32* %retval, align 4  and the type is ddddbbm 28
  br label %return  and the type is ddddbbm 2
  ret i32 %retval1  and the type is ddddbbm 1
0  opt             0x00000000008ed93f
1  opt             0x00000000008edcea
2  libpthread.so.0 0x00007f9ba1183c60
3  opt             0x00000000004b3615 llvm::PATypeHolder::get() const + 21
4  opt             0x00000000008a4f11
5  opt             0x00000000008a9404
6  opt             0x0000000000882557
llvm::FPPassManager::runOnFunction(llvm::Function&) + 551
7  opt             0x00000000008825db
llvm::FPPassManager::runOnModule(llvm::Module&) + 75
8  opt             0x0000000000882197
llvm::MPPassManager::runOnModule(llvm::Module&) + 503
9  opt             0x0000000000882299
llvm::PassManagerImpl::run(llvm::Module&) + 137
10 opt             0x00000000004ac451 main + 4881
11 libc.so.6       0x00007f9ba0459eff __libc_start_main + 255
12 opt             0x000000000049f5f9
Stack dump:
0. Program arguments: opt hello.bc -load
../llvm/llvm-2.9/plugin/BasicBlockStats.so -basic-block-stats -stats -o
newhello.bc
1. Running pass 'Function Pass Manager' on module 'hello.bc'.
2. Running pass 'Module Verifier' on function '@_Z3addii'
Segmentation fault

Please find the source of my pass attached.
Hope to get a reply soon.

Regards,
Arshak Nazaryan
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James Molloy

2011-Nov-03 13:42 UTC

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[LLVMdev] LLVM problem, please do not ignore

Hi Arshak,

 

Do you expect us to debug your pass for you? Have you run it in GDB and seen
where the segfault occurs?

 

3  opt             0x00000000004b3615 llvm::PATypeHolder::get() const + 21

 

Looks like the most likely suspect, run on a bad pointer. But GDB would have
told you this.

 

Also, PATypeHolder is deprecated and not available in mainline trunk.

 

Cheers,

 

James

 

From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On
Behalf Of Arshak Nazaryan
Sent: 03 November 2011 10:56
To: llvmdev at cs.uiuc.edu
Subject: [LLVMdev] LLVM problem, please do not ignore

 

Dear sir or madam,

 

I am a 4-th year student at Yerevan State University, Armenia; and I am
studying LLVM in order to write my Bachelor thesis.

I am trying to write an llvm pass that just removes all "Add" commands
and
gives some statstics. 

Nevertheless, I get this segmentation fault:

 

................some rows about functions, that are not changed by my pass.
The errors occurs after it has modified a "@_Z3addii" function.

store i32 %b.0, i32* %4  and the type is ddddbbm 28

  %5 = load i32* %a_addr, align 4  and the type is ddddbbm 27

  %6 = load i32* %b_addr, align 4  and the type is ddddbbm 27

  %7 = add nsw i32 %5, %6  and the type is ddddbbm 8

  store i32 %7, i32* %0, align 4  and the type is ddddbbm 28

  %7 = add nsw i32 %5, %6   is erased, ba!

  %7 = load i32* %0, align 4  and the type is ddddbbm 27

  store i32 %7, i32* %retval, align 4  and the type is ddddbbm 28

  br label %return  and the type is ddddbbm 2

  ret i32 %retval1  and the type is ddddbbm 1

0  opt             0x00000000008ed93f

1  opt             0x00000000008edcea

2  libpthread.so.0 0x00007f9ba1183c60

3  opt             0x00000000004b3615 llvm::PATypeHolder::get() const + 21

4  opt             0x00000000008a4f11

5  opt             0x00000000008a9404

6  opt             0x0000000000882557
llvm::FPPassManager::runOnFunction(llvm::Function&) + 551

7  opt             0x00000000008825db
llvm::FPPassManager::runOnModule(llvm::Module&) + 75

8  opt             0x0000000000882197
llvm::MPPassManager::runOnModule(llvm::Module&) + 503

9  opt             0x0000000000882299
llvm::PassManagerImpl::run(llvm::Module&) + 137

10 opt             0x00000000004ac451 main + 4881

11 libc.so.6       0x00007f9ba0459eff __libc_start_main + 255

12 opt             0x000000000049f5f9

Stack dump:

0.         Program arguments: opt hello.bc -load
../llvm/llvm-2.9/plugin/BasicBlockStats.so -basic-block-stats -stats -o
newhello.bc 

1.         Running pass 'Function Pass Manager' on module
'hello.bc'.

2.         Running pass 'Module Verifier' on function
'@_Z3addii'

Segmentation fault

 

Please find the source of my pass attached.

Hope to get a reply soon.

 

Regards,

Arshak Nazaryan

 
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Duncan Sands

2011-Nov-03 13:57 UTC

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[LLVMdev] LLVM problem, please do not ignore

Hi Arshak, build LLVM with assertions on.  Then you will get helpful messages
like "Destroying a value while uses still around!" and so on.  You
need to use
replaceAllUsesWith to replace all uses of the add with something else (eg an
undef value of the same type) before you delete it.

Ciao, Duncan.

On 11/03/11 11:55, Arshak Nazaryan wrote:> Dear sir or madam,
>
> I am a 4-th year student at Yerevan State University, Armenia; and I am
studying
> LLVM in order to write my Bachelor thesis.
> I am trying to write an llvm pass that just removes all "Add"
commands and gives
> some statstics.
> Nevertheless, I get this segmentation fault:
>
> ................some rows about functions, that are not changed by my pass.
The
> errors occurs after it has modified a "@_Z3addii" function.
> store i32 %b.0, i32* %4  and the type is ddddbbm 28
>    %5 = load i32* %a_addr, align 4  and the type is ddddbbm 27
>    %6 = load i32* %b_addr, align 4  and the type is ddddbbm 27
>    %7 = add nsw i32 %5, %6  and the type is ddddbbm 8
>    store i32 %7, i32* %0, align 4  and the type is ddddbbm 28
>    %7 = add nsw i32 %5, %6   is erased, ba!
>    %7 = load i32* %0, align 4  and the type is ddddbbm 27
>    store i32 %7, i32* %retval, align 4  and the type is ddddbbm 28
>    br label %return  and the type is ddddbbm 2
>    ret i32 %retval1  and the type is ddddbbm 1
> 0  opt             0x00000000008ed93f
> 1  opt             0x00000000008edcea
> 2  libpthread.so.0 0x00007f9ba1183c60
> 3  opt             0x00000000004b3615 llvm::PATypeHolder::get() const + 21
> 4  opt             0x00000000008a4f11
> 5  opt             0x00000000008a9404
> 6  opt             0x0000000000882557
> llvm::FPPassManager::runOnFunction(llvm::Function&) + 551
> 7  opt             0x00000000008825db
> llvm::FPPassManager::runOnModule(llvm::Module&) + 75
> 8  opt             0x0000000000882197
> llvm::MPPassManager::runOnModule(llvm::Module&) + 503
> 9  opt             0x0000000000882299
llvm::PassManagerImpl::run(llvm::Module&)
> + 137
> 10 opt             0x00000000004ac451 main + 4881
> 11 libc.so.6       0x00007f9ba0459eff __libc_start_main + 255
> 12 opt             0x000000000049f5f9
> Stack dump:
> 0.Program arguments: opt hello.bc -load
> ../llvm/llvm-2.9/plugin/BasicBlockStats.so -basic-block-stats -stats -o
newhello.bc
> 1.Running pass 'Function Pass Manager' on module
'hello.bc'.
> 2.Running pass 'Module Verifier' on function '@_Z3addii'
> Segmentation fault
>
> Please find the source of my pass attached.
> Hope to get a reply soon.
>
> Regards,
> Arshak Nazaryan
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

John Criswell

2011-Nov-03 14:43 UTC

head link

[LLVMdev] LLVM problem, please do not ignore

On 11/3/2011 4:55 AM, Arshak Nazaryan wrote:> Dear sir or madam,
>
> I am a 4-th year student at Yerevan State University, Armenia; and I 
> am studying LLVM in order to write my Bachelor thesis.
Hi Arshak.

> I am trying to write an llvm pass that just removes all "Add"
commands
> and gives some statstics.
> Nevertheless, I get this segmentation fault:
The problem is most likely that you're not modifying uses of the add 
instructions.  The LLVM IR has explicit def-use chains, so if you want 
to remove an instruction, you need to modify any other instruction *that 
uses that instruction* so that it does not use that instruction any more.

In this case, an instruction that is using the add instruction will 
still reference the add instruction even after you've deleted it.  The 
error you're seeing is most likely due to a dangling pointer.

To fix it, create a constant integer (ConstantInt object) and use the 
replaceAllUsesWith() method of the Instruction class to replace uses of 
the add with the integer.  Then you can erase the add from the program.

By the way, it looks like you don't have a build with assertions 
enabled.  I recommend compiling with

gmake ENABLE_OPTIMIZED=0 DISABLE_ASSERTIONS=1

if you're going to be developing an LLVM pass.

-- John T.
>
> ................some rows about functions, that are not changed by my 
> pass. The errors occurs after it has modified a "@_Z3addii"
function.
> store i32 %b.0, i32* %4  and the type is ddddbbm 28
>   %5 = load i32* %a_addr, align 4  and the type is ddddbbm 27
>   %6 = load i32* %b_addr, align 4  and the type is ddddbbm 27
>   %7 = add nsw i32 %5, %6  and the type is ddddbbm 8
>   store i32 %7, i32* %0, align 4  and the type is ddddbbm 28
>   %7 = add nsw i32 %5, %6   is erased, ba!
>   %7 = load i32* %0, align 4  and the type is ddddbbm 27
>   store i32 %7, i32* %retval, align 4  and the type is ddddbbm 28
>   br label %return  and the type is ddddbbm 2
>   ret i32 %retval1  and the type is ddddbbm 1
> 0  opt             0x00000000008ed93f
> 1  opt             0x00000000008edcea
> 2  libpthread.so.0 0x00007f9ba1183c60
> 3  opt             0x00000000004b3615 llvm::PATypeHolder::get() const + 21
> 4  opt             0x00000000008a4f11
> 5  opt             0x00000000008a9404
> 6  opt             0x0000000000882557 
> llvm::FPPassManager::runOnFunction(llvm::Function&) + 551
> 7  opt             0x00000000008825db 
> llvm::FPPassManager::runOnModule(llvm::Module&) + 75
> 8  opt             0x0000000000882197 
> llvm::MPPassManager::runOnModule(llvm::Module&) + 503
> 9  opt             0x0000000000882299 
> llvm::PassManagerImpl::run(llvm::Module&) + 137
> 10 opt             0x00000000004ac451 main + 4881
> 11 libc.so.6       0x00007f9ba0459eff __libc_start_main + 255
> 12 opt             0x000000000049f5f9
> Stack dump:
> 0.Program arguments: opt hello.bc -load 
> ../llvm/llvm-2.9/plugin/BasicBlockStats.so -basic-block-stats -stats 
> -o newhello.bc
> 1.Running pass 'Function Pass Manager' on module
'hello.bc'.
> 2.Running pass 'Module Verifier' on function '@_Z3addii'
> Segmentation fault
>
> Please find the source of my pass attached.
> Hope to get a reply soon.
>
> Regards,
> Arshak Nazaryan
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
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Michael Smith

2011-Nov-03 16:21 UTC

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[LLVMdev] LLVM problem, please do not ignore

You probably have dangling references to the instructions you removed. Before
erasing the instruction, you should call replaceAllUsesWith(Value *v) to remove
any references in other instructions.

Regards,
Michael Smith

From: Arshak Nazaryan [mailto:arshak.info at gmail.com]
Sent: Thursday, November 03, 2011 3:56 AM
To: llvmdev at cs.uiuc.edu
Subject: [LLVMdev] LLVM problem, please do not ignore

Dear sir or madam,

I am a 4-th year student at Yerevan State University, Armenia; and I am studying
LLVM in order to write my Bachelor thesis.
I am trying to write an llvm pass that just removes all "Add" commands
and gives some statstics.
Nevertheless, I get this segmentation fault:

................some rows about functions, that are not changed by my pass. The
errors occurs after it has modified a "@_Z3addii" function.
store i32 %b.0, i32* %4  and the type is ddddbbm 28
  %5 = load i32* %a_addr, align 4  and the type is ddddbbm 27
  %6 = load i32* %b_addr, align 4  and the type is ddddbbm 27
  %7 = add nsw i32 %5, %6  and the type is ddddbbm 8
  store i32 %7, i32* %0, align 4  and the type is ddddbbm 28
  %7 = add nsw i32 %5, %6   is erased, ba!
  %7 = load i32* %0, align 4  and the type is ddddbbm 27
  store i32 %7, i32* %retval, align 4  and the type is ddddbbm 28
  br label %return  and the type is ddddbbm 2
  ret i32 %retval1  and the type is ddddbbm 1
0  opt             0x00000000008ed93f
1  opt             0x00000000008edcea
2  libpthread.so.0 0x00007f9ba1183c60
3  opt             0x00000000004b3615 llvm::PATypeHolder::get() const + 21
4  opt             0x00000000008a4f11
5  opt             0x00000000008a9404
6  opt             0x0000000000882557
llvm::FPPassManager::runOnFunction(llvm::Function&) + 551
7  opt             0x00000000008825db
llvm::FPPassManager::runOnModule(llvm::Module&) + 75
8  opt             0x0000000000882197
llvm::MPPassManager::runOnModule(llvm::Module&) + 503
9  opt             0x0000000000882299
llvm::PassManagerImpl::run(llvm::Module&) + 137
10 opt             0x00000000004ac451 main + 4881
11 libc.so.6       0x00007f9ba0459eff __libc_start_main + 255
12 opt             0x000000000049f5f9
Stack dump:
0.         Program arguments: opt hello.bc -load
../llvm/llvm-2.9/plugin/BasicBlockStats.so -basic-block-stats -stats -o
newhello.bc
1.         Running pass 'Function Pass Manager' on module
'hello.bc'.
2.         Running pass 'Module Verifier' on function
'@_Z3addii'
Segmentation fault

Please find the source of my pass attached.
Hope to get a reply soon.

Regards,
Arshak Nazaryan

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