Extracting operand name and value from GIMPLE assignment statements

Extracting operand name and value from GIMPLE assignment statements

[Sandeep K Chaudhary]

Hi Guys,

I am writing a GCC plugin in which I need to extract the variable name
and the assigned value from the statements.

I am able to get the three operands from GIMPLE statements like this

        if(is_gimple_assign(stmt)) {
                tree lhsop = gimple_assign_lhs(stmt);
                tree rhsop1 = gimple_assign_rhs1(stmt);
                tree rhsop2 = gimple_assign_rhs2(stmt);
         }

I want to get the exact variable name from lhsop and value from rhsop1
(for statements such as
"var = value;", rhsop2 is 0 for such statements.). Some pointers to
example code or documentation would be great. I can't find anything
similar in

http://gcc.gnu.org/onlinedocs/gccint/Manipulating-GIMPLE-statements.html

Thanks a lot !

Regards,
Sandeep K Chaudhary.

Re: Extracting operand name and value from GIMPLE assignment statements

[Ian Lance Taylor]

On Mon, Dec 9, 2013 at 3:05 PM, Sandeep K Chaudhary
<babbusandy2006@gmail.com> wrote:
>
> I am writing a GCC plugin in which I need to extract the variable name
> and the assigned value from the statements.
>
> I am able to get the three operands from GIMPLE statements like this
>
>         if(is_gimple_assign(stmt)) {
>                 tree lhsop = gimple_assign_lhs(stmt);
>                 tree rhsop1 = gimple_assign_rhs1(stmt);
>                 tree rhsop2 = gimple_assign_rhs2(stmt);
>          }
>
> I want to get the exact variable name from lhsop and value from rhsop1
> (for statements such as
> "var = value;", rhsop2 is 0 for such statements.). Some pointers to
> example code or documentation would be great.

Can you expand on what you mean by the variable name?  GCC freely
introduces and discards variables in GIMPLE.  Many GIMPLE variables do
not have any meaningful name.

Ian

Re: Extracting operand name and value from GIMPLE assignment statements

[Sandeep K Chaudhary]

Hi Ian,

Thanks for the reply !

I mean that I am interested in knowing the name of variables from the
code. For example - if there is a statement in the C code like this -

"VAR_A = 100;"

I would like to know the name of the variable i.e. "VAR_A" in the
GIMPLE statement. Please let me know how this can be achieved.

Thanks and regards,
Sandeep.

On Mon, Dec 9, 2013 at 9:13 PM, Ian Lance Taylor <iant@google.com> wrote:
> On Mon, Dec 9, 2013 at 3:05 PM, Sandeep K Chaudhary
> <babbusandy2006@gmail.com> wrote:
>>
>> I am writing a GCC plugin in which I need to extract the variable name
>> and the assigned value from the statements.
>>
>> I am able to get the three operands from GIMPLE statements like this
>>
>>         if(is_gimple_assign(stmt)) {
>>                 tree lhsop = gimple_assign_lhs(stmt);
>>                 tree rhsop1 = gimple_assign_rhs1(stmt);
>>                 tree rhsop2 = gimple_assign_rhs2(stmt);
>>          }
>>
>> I want to get the exact variable name from lhsop and value from rhsop1
>> (for statements such as
>> "var = value;", rhsop2 is 0 for such statements.). Some pointers to
>> example code or documentation would be great.
>
> Can you expand on what you mean by the variable name?  GCC freely
> introduces and discards variables in GIMPLE.  Many GIMPLE variables do
> not have any meaningful name.
>
> Ian



-- 
Thanks and regards,
Sandeep K Chaudhary.

Re: Extracting operand name and value from GIMPLE assignment statements

[Ian Lance Taylor]

On Mon, Dec 9, 2013 at 6:35 PM, Sandeep K Chaudhary
<babbusandy2006@gmail.com> wrote:
>
> I mean that I am interested in knowing the name of variables from the code.
> For example - if there is a statement in the C code like this -
>
> "VAR_A = 100;"
>
> I would like to know the name of the variable i.e. "VAR_A" in the GIMPLE
> statement. Please let me know how this can be achieved.

In general, when in GIMPLE, there is no answer to that question.
GIMPLE translates your program into SSA form, so every variable is set
only once.  It follows that every local variable is a temporary
variable, with no name that is meaningful in the source code.  There
is debug info to track variable values, but it is tracked separately
from the GIMPLE statements.

Ian




> On Mon, Dec 9, 2013 at 9:13 PM, Ian Lance Taylor <iant@google.com> wrote:
>>
>> On Mon, Dec 9, 2013 at 3:05 PM, Sandeep K Chaudhary
>> <babbusandy2006@gmail.com> wrote:
>> >
>> > I am writing a GCC plugin in which I need to extract the variable name
>> > and the assigned value from the statements.
>> >
>> > I am able to get the three operands from GIMPLE statements like this
>> >
>> >         if(is_gimple_assign(stmt)) {
>> >                 tree lhsop = gimple_assign_lhs(stmt);
>> >                 tree rhsop1 = gimple_assign_rhs1(stmt);
>> >                 tree rhsop2 = gimple_assign_rhs2(stmt);
>> >          }
>> >
>> > I want to get the exact variable name from lhsop and value from rhsop1
>> > (for statements such as
>> > "var = value;", rhsop2 is 0 for such statements.). Some pointers to
>> > example code or documentation would be great.
>>
>> Can you expand on what you mean by the variable name?  GCC freely
>> introduces and discards variables in GIMPLE.  Many GIMPLE variables do
>> not have any meaningful name.
>>
>> Ian
>
>
>
>
> --
> Thanks and regards,
> Sandeep K Chaudhary.

Re: Extracting operand name and value from GIMPLE assignment statements

[Sandeep K Chaudhary]

Hi Ian,

I understand that the variables in SSA are different but as you said
but I hoped to track the variables from the debug info. Is it not
feasible to track the debug info?

I have been able to achieve this kind of functionality with LLVM using
its LLVM IR of the program. The debug info is easily usable and
provides info about the IR statements with respect to the source code.
I want to write the pass in GCC that's why I hoped that I can somehow
achieve it in GCC. Please let me know your thoughts.

Thanks a lot !

Regards,
Sandeep.

On Tue, Dec 10, 2013 at 1:06 AM, Ian Lance Taylor <iant@google.com> wrote:
> On Mon, Dec 9, 2013 at 6:35 PM, Sandeep K Chaudhary
> <babbusandy2006@gmail.com> wrote:
>>
>> I mean that I am interested in knowing the name of variables from the code.
>> For example - if there is a statement in the C code like this -
>>
>> "VAR_A = 100;"
>>
>> I would like to know the name of the variable i.e. "VAR_A" in the GIMPLE
>> statement. Please let me know how this can be achieved.
>
> In general, when in GIMPLE, there is no answer to that question.
> GIMPLE translates your program into SSA form, so every variable is set
> only once.  It follows that every local variable is a temporary
> variable, with no name that is meaningful in the source code.  There
> is debug info to track variable values, but it is tracked separately
> from the GIMPLE statements.
>
> Ian
>
>
>
>
>> On Mon, Dec 9, 2013 at 9:13 PM, Ian Lance Taylor <iant@google.com> wrote:
>>>
>>> On Mon, Dec 9, 2013 at 3:05 PM, Sandeep K Chaudhary
>>> <babbusandy2006@gmail.com> wrote:
>>> >
>>> > I am writing a GCC plugin in which I need to extract the variable name
>>> > and the assigned value from the statements.
>>> >
>>> > I am able to get the three operands from GIMPLE statements like this
>>> >
>>> >         if(is_gimple_assign(stmt)) {
>>> >                 tree lhsop = gimple_assign_lhs(stmt);
>>> >                 tree rhsop1 = gimple_assign_rhs1(stmt);
>>> >                 tree rhsop2 = gimple_assign_rhs2(stmt);
>>> >          }
>>> >
>>> > I want to get the exact variable name from lhsop and value from rhsop1
>>> > (for statements such as
>>> > "var = value;", rhsop2 is 0 for such statements.). Some pointers to
>>> > example code or documentation would be great.
>>>
>>> Can you expand on what you mean by the variable name?  GCC freely
>>> introduces and discards variables in GIMPLE.  Many GIMPLE variables do
>>> not have any meaningful name.
>>>
>>> Ian
>>
>>
>>
>>
>> --
>> Thanks and regards,
>> Sandeep K Chaudhary.



-- 
Thanks and regards,
Sandeep K Chaudhary.

Re: Extracting operand name and value from GIMPLE assignment statements

[Ian Lance Taylor]

On Tue, Dec 10, 2013 at 12:21 AM, Sandeep K Chaudhary
<babbusandy2006@gmail.com> wrote:
>
> I understand that the variables in SSA are different but as you said
> but I hoped to track the variables from the debug info. Is it not
> feasible to track the debug info?
>
> I have been able to achieve this kind of functionality with LLVM using
> its LLVM IR of the program. The debug info is easily usable and
> provides info about the IR statements with respect to the source code.
> I want to write the pass in GCC that's why I hoped that I can somehow
> achieve it in GCC. Please let me know your thoughts.

Please don't top-post.  Thanks.

Yes, you can track the debug info, you just can't do it by pulling
apart the GIMPLE instructions you are looking at.  You need to also
look for GIMPLE_DEBUG instructions.  The GIMPLE_DEBUG_BIND and
GIMPLE_DEBUG_SOURCE_BIND ops will help you map the gimple vars back to
the source vars.

This is not an area of the compiler that I know much about.

Ian

> On Tue, Dec 10, 2013 at 1:06 AM, Ian Lance Taylor <iant@google.com> wrote:
>> On Mon, Dec 9, 2013 at 6:35 PM, Sandeep K Chaudhary
>> <babbusandy2006@gmail.com> wrote:
>>>
>>> I mean that I am interested in knowing the name of variables from the code.
>>> For example - if there is a statement in the C code like this -
>>>
>>> "VAR_A = 100;"
>>>
>>> I would like to know the name of the variable i.e. "VAR_A" in the GIMPLE
>>> statement. Please let me know how this can be achieved.
>>
>> In general, when in GIMPLE, there is no answer to that question.
>> GIMPLE translates your program into SSA form, so every variable is set
>> only once.  It follows that every local variable is a temporary
>> variable, with no name that is meaningful in the source code.  There
>> is debug info to track variable values, but it is tracked separately
>> from the GIMPLE statements.
>>
>> Ian
>>
>>
>>
>>
>>> On Mon, Dec 9, 2013 at 9:13 PM, Ian Lance Taylor <iant@google.com> wrote:
>>>>
>>>> On Mon, Dec 9, 2013 at 3:05 PM, Sandeep K Chaudhary
>>>> <babbusandy2006@gmail.com> wrote:
>>>> >
>>>> > I am writing a GCC plugin in which I need to extract the variable name
>>>> > and the assigned value from the statements.
>>>> >
>>>> > I am able to get the three operands from GIMPLE statements like this
>>>> >
>>>> >         if(is_gimple_assign(stmt)) {
>>>> >                 tree lhsop = gimple_assign_lhs(stmt);
>>>> >                 tree rhsop1 = gimple_assign_rhs1(stmt);
>>>> >                 tree rhsop2 = gimple_assign_rhs2(stmt);
>>>> >          }
>>>> >
>>>> > I want to get the exact variable name from lhsop and value from rhsop1
>>>> > (for statements such as
>>>> > "var = value;", rhsop2 is 0 for such statements.). Some pointers to
>>>> > example code or documentation would be great.
>>>>
>>>> Can you expand on what you mean by the variable name?  GCC freely
>>>> introduces and discards variables in GIMPLE.  Many GIMPLE variables do
>>>> not have any meaningful name.
>>>>
>>>> Ian
>>>
>>>
>>>
>>>
>>> --
>>> Thanks and regards,
>>> Sandeep K Chaudhary.
>
>
>
> --
> Thanks and regards,
> Sandeep K Chaudhary.

Re: Extracting operand name and value from GIMPLE assignment statements

[Sandeep K Chaudhary]

Ok, thanks a lot for the info, Ian ! I will look into these and try to
figure things out.

Thanks and regards,
Sandeep.

Extracting operand name and value from GIMPLE assignment statements

[Sandeep K Chaudhary]

Hi Guys,

I am writing a GCC plugin in which I need to extract the variable name
and the assigned value from the statements.

I am able to get the three operands from GIMPLE statements like this

        if(is_gimple_assign(stmt)) {
                tree lhsop = gimple_assign_lhs(stmt);
                tree rhsop1 = gimple_assign_rhs1(stmt);
                tree rhsop2 = gimple_assign_rhs2(stmt);
         }

I want to get the exact variable name from lhsop and value from rhsop1
(for statements such as
"var = value;", rhsop2 is 0 for such statements.). Some pointers to
example code or documentation would be great. I can't find anything
similar in

http://gcc.gnu.org/onlinedocs/gccint/Manipulating-GIMPLE-statements.html

Thanks a lot !

Regards,
Sandeep K Chaudhary.