how to write __asm__ goto inline assembly

how to write asm goto inline assembly

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I m using a GCC compiler. I want to insert some inline instructions into C. Non-branching instructions are inserted successfully using __asm__ directive, as follows:

  __asm__ volatile (

            "add %[my_out], %[my_op1], %[my_op2]n"

            : [my_out] "=&r" (array[3])

            : [my_op1] "r" (array[0]),[my_op2] "r" (array[1])

    );

But i cant inset a branch/jump instruction. Compilation gives the following error:

../test.c:5: error: expected '(' before 'goto'

../test.c:5: error: expected identifier or '*' before 'volatile'

I tried the following code:

unsigned int array[10] = { 0x22, 0x12,0,0,0,0,0,0,0};

int main() {





  __asm__ goto volatile (

                "jp %l[label]n"

                : /*no output*/

                : [my_op1] "r" (array[0]),[my_op2] "r" (array[1])

                : /*no cobblers*/

                : label

        );





  return 0;



label:



  __asm__ volatile (

                "add %[my_out], %[my_op1], %[my_op2]n"

                : [my_out] "=&r" (array[3])

                : [my_op1] "r" (array[0]),[my_op2] "r" (array[1])

        );





  return 0;



}

can you please help in correcting this code?
Regards

asked Nov 21 at 8:19

Sajjad

276

1

place volatile keyword before goto rather than after.In your case you can remove the volatile in your first statement given that you have no output (or input/output) constraints. When you have none of those asm is has an implicit volatile. Your second asm would still have to be marked volatile
– Michael Petch
Nov 21 at 9:02

1

To add to what Michael said, since asm goto cannot have outputs, and since asm statements without outputs are implicitly volatile, all asm goto statements are implicitly volatile. You might also want to check out the docs which would have shown you the order for the qualifiers.
– David Wohlferd
Nov 21 at 9:22

1

That should have worked. What's your target hw/os? And what version of gcc are you using?
– David Wohlferd
Nov 21 at 10:32

1

What version of GCC are you using? You can use gcc -v to find out. When you made the fix suggested did the error change?
– Michael Petch
Nov 21 at 10:53

2

asm goto wasn't available until GCC 4.5
– Michael Petch
Nov 21 at 12:53

|
show 6 more comments

up vote
1
down vote

favorite

I m using a GCC compiler. I want to insert some inline instructions into C. Non-branching instructions are inserted successfully using __asm__ directive, as follows:

  __asm__ volatile (

            "add %[my_out], %[my_op1], %[my_op2]n"

            : [my_out] "=&r" (array[3])

            : [my_op1] "r" (array[0]),[my_op2] "r" (array[1])

    );

But i cant inset a branch/jump instruction. Compilation gives the following error:

../test.c:5: error: expected '(' before 'goto'

../test.c:5: error: expected identifier or '*' before 'volatile'

I tried the following code:

unsigned int array[10] = { 0x22, 0x12,0,0,0,0,0,0,0};

int main() {





  __asm__ goto volatile (

                "jp %l[label]n"

                : /*no output*/

                : [my_op1] "r" (array[0]),[my_op2] "r" (array[1])

                : /*no cobblers*/

                : label

        );





  return 0;



label:



  __asm__ volatile (

                "add %[my_out], %[my_op1], %[my_op2]n"

                : [my_out] "=&r" (array[3])

                : [my_op1] "r" (array[0]),[my_op2] "r" (array[1])

        );





  return 0;



}

can you please help in correcting this code?
Regards

asked Nov 21 at 8:19

Sajjad

276

1

place volatile keyword before goto rather than after.In your case you can remove the volatile in your first statement given that you have no output (or input/output) constraints. When you have none of those asm is has an implicit volatile. Your second asm would still have to be marked volatile
– Michael Petch
Nov 21 at 9:02

1

To add to what Michael said, since asm goto cannot have outputs, and since asm statements without outputs are implicitly volatile, all asm goto statements are implicitly volatile. You might also want to check out the docs which would have shown you the order for the qualifiers.
– David Wohlferd
Nov 21 at 9:22

1

That should have worked. What's your target hw/os? And what version of gcc are you using?
– David Wohlferd
Nov 21 at 10:32

1

What version of GCC are you using? You can use gcc -v to find out. When you made the fix suggested did the error change?
– Michael Petch
Nov 21 at 10:53

2

asm goto wasn't available until GCC 4.5
– Michael Petch
Nov 21 at 12:53

|
show 6 more comments

up vote
1
down vote

favorite

I m using a GCC compiler. I want to insert some inline instructions into C. Non-branching instructions are inserted successfully using __asm__ directive, as follows:

  __asm__ volatile (

            "add %[my_out], %[my_op1], %[my_op2]n"

            : [my_out] "=&r" (array[3])

            : [my_op1] "r" (array[0]),[my_op2] "r" (array[1])

    );

But i cant inset a branch/jump instruction. Compilation gives the following error:

../test.c:5: error: expected '(' before 'goto'

../test.c:5: error: expected identifier or '*' before 'volatile'

I tried the following code:

unsigned int array[10] = { 0x22, 0x12,0,0,0,0,0,0,0};

int main() {





  __asm__ goto volatile (

                "jp %l[label]n"

                : /*no output*/

                : [my_op1] "r" (array[0]),[my_op2] "r" (array[1])

                : /*no cobblers*/

                : label

        );





  return 0;



label:



  __asm__ volatile (

                "add %[my_out], %[my_op1], %[my_op2]n"

                : [my_out] "=&r" (array[3])

                : [my_op1] "r" (array[0]),[my_op2] "r" (array[1])

        );





  return 0;



}

can you please help in correcting this code?
Regards

asked Nov 21 at 8:19

Sajjad

276

I m using a GCC compiler. I want to insert some inline instructions into C. Non-branching instructions are inserted successfully using __asm__ directive, as follows:

  __asm__ volatile (

            "add %[my_out], %[my_op1], %[my_op2]n"

            : [my_out] "=&r" (array[3])

            : [my_op1] "r" (array[0]),[my_op2] "r" (array[1])

    );

But i cant inset a branch/jump instruction. Compilation gives the following error:

../test.c:5: error: expected '(' before 'goto'

../test.c:5: error: expected identifier or '*' before 'volatile'

I tried the following code:

unsigned int array[10] = { 0x22, 0x12,0,0,0,0,0,0,0};

int main() {





  __asm__ goto volatile (

                "jp %l[label]n"

                : /*no output*/

                : [my_op1] "r" (array[0]),[my_op2] "r" (array[1])

                : /*no cobblers*/

                : label

        );





  return 0;



label:



  __asm__ volatile (

                "add %[my_out], %[my_op1], %[my_op2]n"

                : [my_out] "=&r" (array[3])

                : [my_op1] "r" (array[0]),[my_op2] "r" (array[1])

        );





  return 0;



}

can you please help in correcting this code?
Regards

gcc inline-assembly

asked Nov 21 at 8:19

Sajjad

276

asked Nov 21 at 8:19

Sajjad

276

asked Nov 21 at 8:19

Sajjad

276

asked Nov 21 at 8:19

Sajjad

276

asked Nov 21 at 8:19

Sajjad

276

1

place volatile keyword before goto rather than after.In your case you can remove the volatile in your first statement given that you have no output (or input/output) constraints. When you have none of those asm is has an implicit volatile. Your second asm would still have to be marked volatile
– Michael Petch
Nov 21 at 9:02

1

To add to what Michael said, since asm goto cannot have outputs, and since asm statements without outputs are implicitly volatile, all asm goto statements are implicitly volatile. You might also want to check out the docs which would have shown you the order for the qualifiers.
– David Wohlferd
Nov 21 at 9:22

1

That should have worked. What's your target hw/os? And what version of gcc are you using?
– David Wohlferd
Nov 21 at 10:32

1

What version of GCC are you using? You can use gcc -v to find out. When you made the fix suggested did the error change?
– Michael Petch
Nov 21 at 10:53

2

asm goto wasn't available until GCC 4.5
– Michael Petch
Nov 21 at 12:53

|
show 6 more comments

1

place volatile keyword before goto rather than after.In your case you can remove the volatile in your first statement given that you have no output (or input/output) constraints. When you have none of those asm is has an implicit volatile. Your second asm would still have to be marked volatile
– Michael Petch
Nov 21 at 9:02

1

To add to what Michael said, since asm goto cannot have outputs, and since asm statements without outputs are implicitly volatile, all asm goto statements are implicitly volatile. You might also want to check out the docs which would have shown you the order for the qualifiers.
– David Wohlferd
Nov 21 at 9:22

1

That should have worked. What's your target hw/os? And what version of gcc are you using?
– David Wohlferd
Nov 21 at 10:32

1

What version of GCC are you using? You can use gcc -v to find out. When you made the fix suggested did the error change?
– Michael Petch
Nov 21 at 10:53

2

asm goto wasn't available until GCC 4.5
– Michael Petch
Nov 21 at 12:53

place volatile keyword before goto rather than after.In your case you can remove the volatile in your first statement given that you have no output (or input/output) constraints. When you have none of those asm is has an implicit volatile. Your second asm would still have to be marked volatile
– Michael Petch
Nov 21 at 9:02

To add to what Michael said, since asm goto cannot have outputs, and since asm statements without outputs are implicitly volatile, all asm goto statements are implicitly volatile. You might also want to check out the docs which would have shown you the order for the qualifiers.
– David Wohlferd
Nov 21 at 9:22

That should have worked. What's your target hw/os? And what version of gcc are you using?
– David Wohlferd
Nov 21 at 10:32

What version of GCC are you using? You can use gcc -v to find out. When you made the fix suggested did the error change?
– Michael Petch
Nov 21 at 10:53

asm goto wasn't available until GCC 4.5
– Michael Petch
Nov 21 at 12:53

|
show 6 more comments

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