Data-flow informations (CFG)

Data-flow informations (CFG)

[Harry Trinta]

Dear,

A program can be represented by a CFG (Control Flow Graph).
Within source file Profile.c, for example, is easy to navigate within
CFG and obtain certain information.
However, I would like some more specific information, for example,
what are the the declarations and what are the uses of variables
within a given node of the CFG.

Can I get this information somewhere in the building?

The goal is to calculate the viability of creating a "module" for
software testing based on the data flow.

Thanks,
Harry

Re: Data-flow informations (CFG)

[Ian Lance Taylor]

Harry Trinta <harrytpc@gmail.com> writes:

> A program can be represented by a CFG (Control Flow Graph).
> Within source file Profile.c, for example, is easy to navigate within
> CFG and obtain certain information.
> However, I would like some more specific information, for example,
> what are the the declarations and what are the uses of variables
> within a given node of the CFG.
>
> Can I get this information somewhere in the building?
>
> The goal is to calculate the viability of creating a "module" for
> software testing based on the data flow.

The CFG doesn't have any declarations.  In effect all declarations are
moved to the outer-most block of a function, renamed as necessary.

You can indeed find the uses of variables within a block of the CFG, by
scanning the instructions in the block.

Ian

Re: Data-flow informations (CFG)

[Harry Trinta]

> The CFG doesn't have any declarations.  In effect all declarations are
> moved to the outer-most block of a function, renamed as necessary.

Truth. The CFC of GCC does not have the statements. =(

I know that declarations is not in a block of the CFG in fact. But if
we analyze the code, a declaration always is a "part" of a block too.
So, there is no way to see in which block a declaration was made?

Thanks,
Harry

2011/10/25 Ian Lance Taylor <iant@google.com>:
> Harry Trinta <harrytpc@gmail.com> writes:
>
>> A program can be represented by a CFG (Control Flow Graph).
>> Within source file Profile.c, for example, is easy to navigate within
>> CFG and obtain certain information.
>> However, I would like some more specific information, for example,
>> what are the the declarations and what are the uses of variables
>> within a given node of the CFG.
>>
>> Can I get this information somewhere in the building?
>>
>> The goal is to calculate the viability of creating a "module" for
>> software testing based on the data flow.
>
> The CFG doesn't have any declarations.  In effect all declarations are
> moved to the outer-most block of a function, renamed as necessary.
>
> You can indeed find the uses of variables within a block of the CFG, by
> scanning the instructions in the block.
>
> Ian
>

Re: Data-flow informations (CFG)

[Harry Trinta]

> The CFG doesn't have any declarations.  In effect all declarations are
> moved to the outer-most block of a function, renamed as necessary.

Truth. The CFC of GCC does not have the DECLARATIONS. =(

I know that declarations is not in a block of the CFG in fact. But if
we analyze the code, a declaration always is a "part" of a block too.
So, there is no way to see in which block a declaration was made?

Thanks,
Harry


> 2011/10/25 Ian Lance Taylor <iant@google.com>:
>> Harry Trinta <harrytpc@gmail.com> writes:
>>
>>> A program can be represented by a CFG (Control Flow Graph).
>>> Within source file Profile.c, for example, is easy to navigate within
>>> CFG and obtain certain information.
>>> However, I would like some more specific information, for example,
>>> what are the the declarations and what are the uses of variables
>>> within a given node of the CFG.
>>>
>>> Can I get this information somewhere in the building?
>>>
>>> The goal is to calculate the viability of creating a "module" for
>>> software testing based on the data flow.
>>
>> The CFG doesn't have any declarations.  In effect all declarations are
>> moved to the outer-most block of a function, renamed as necessary.
>>
>> You can indeed find the uses of variables within a block of the CFG, by
>> scanning the instructions in the block.
>>
>> Ian
>>
>

Re: Data-flow informations (CFG)

[Ian Lance Taylor]

Harry Trinta <harrytpc@gmail.com> writes:

>> The CFG doesn't have any declarations.  In effect all declarations are
>> moved to the outer-most block of a function, renamed as necessary.
>
> Truth. The CFC of GCC does not have the DECLARATIONS. =(
>
> I know that declarations is not in a block of the CFG in fact. But if
> we analyze the code, a declaration always is a "part" of a block too.
> So, there is no way to see in which block a declaration was made?

Assuming we are talking about C or C++, then if you look at GENERIC
immediately after parsing, you can find the declarations by looking for
DECL_EXPR statements.  However, at that point there is no CFG, and the
DECL_EXPR statements are dropped when moving to GIMPLE.  So, no, gcc
does not have any representation of the program which includes both a
CFG and records which block contains a declaration.  At least as far as
I know.

Ian