Re: target/6039: ARM interrupt attribute generats wrong code

Re: target/6039: ARM interrupt attribute generats wrong code

[mmitchel]

Synopsis: ARM interrupt attribute generats wrong code

State-Changed-From-To: open->analyzed
State-Changed-By: mmitchel
State-Changed-When: Thu Apr 18 09:03:27 2002
State-Changed-Why:
    Confirmed.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=6039

Re: target/6039: [ARM] interrupt attribute generats wrong code

[giovannibajo]

Synopsis: [ARM] interrupt attribute generats wrong code

State-Changed-From-To: analyzed->feedback
State-Changed-By: bajo
State-Changed-When: Sat May 17 06:58:54 2003
State-Changed-Why:
    See Dara's question.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=6039

Re: target/6039: [ARM] interrupt attribute generats wrong code

[Dara Hazeghi]

The following reply was made to PR target/6039; it has been noted by GNATS.

From: Dara Hazeghi <dhazeghi@yahoo.com>
To: tori@unhappy.mine.nu, gcc-gnats@gcc.gnu.org, nobody@gcc.gnu.org
Cc:  
Subject: Re: target/6039: [ARM] interrupt attribute generats wrong code
Date: Fri, 16 May 2003 19:48:47 -0700

 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit- 
 trail&database=gcc&pr=6039
 
 Hello,
 
 gcc 3.0.4 and 3.1 cvs are rather ancient at this point. Would it be  
 possible for you to check whether this problem is still present. I  
 don't know much about arm assembly, but this is what 3.3 produces:
          .file   "junk.c"
          .text
          .align  2
          .global foo
          .type   foo, %function
 foo:
          @ Interrupt Service Routine.
          @ args = 0, pretend = 0, frame = 12
          @ frame_needed = 1, uses_anonymous_args = 0
          str     ip, [sp, #-4]!
          mov     ip, sp
          sub     lr, lr, #4
          stmfd   sp!, {r0, r1, r2, r3, fp, ip, lr, pc}
          sub     fp, ip, #4
          sub     sp, sp, #12
          mov     r3, #0
          str     r3, [fp, #-40]
          mov     r3, #0
          str     r3, [fp, #-44]
          ldr     r2, [fp, #-40]
          ldr     r3, [fp, #-44]
          add     r3, r2, r3
          str     r3, [fp, #-48]
          bl      bar
          ldmea   fp, {r0, r1, r2, r3, fp, ip, pc}^
          .size   foo, .-foo
          .ident  "GCC: (GNU) 3.3 20030508 (prerelease)"
 
 gcc mainline produces:
          .file   "junk.c"
          .text
          .align  2
          .global foo
          .type   foo, %function
 foo:
          @ Interrupt Service Routine.
          @ args = 0, pretend = 0, frame = 12
          @ frame_needed = 1, uses_anonymous_args = 0
          str     ip, [sp, #-4]!
          mov     ip, sp
          stmfd   sp!, {r0, r1, r2, r3, fp, ip, lr, pc}
          sub     fp, ip, #4
          sub     sp, sp, #12
          mov     r3, #0
          str     r3, [fp, #-40]
          mov     r3, #0
          str     r3, [fp, #-44]
          ldr     r2, [fp, #-40]
          ldr     r3, [fp, #-44]
          add     r3, r2, r3
          str     r3, [fp, #-48]
          bl      bar
          ldmea   fp, {r0, r1, r2, r3, fp, sp, lr}
          ldmfd   sp!, {ip}
          subs    pc, lr, #4
          .size   foo, .-foo
          .ident  "GCC: (GNU) 3.4 20030508 (experimental)"
 
 
 Can you confirm if these are correct? Thanks,
 
 Dara
 

target/6039: ARM interrupt attribute generats wrong code

[tori]

>Number:         6039
>Category:       target
>Synopsis:       ARM interrupt attribute generats wrong code
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Fri Mar 22 07:56:00 PST 2002
>Closed-Date:
>Last-Modified:
>Originator:     Tobias Ringstrom
>Release:        gcc-3.0.4
>Organization:
>Environment:
Crosscompiler for arm-elf (cygwin and Linux host)
>Description:
Compile the following code with arm-elf-gcc -S tmp.c:

void foo(void) __attribute__((__interrupt__));
void bar(void);
void foo()
{
        int a=0, b=0, c=a+b;
        bar();
}

gives you the following:

@ Generated by gcc 3.0.4 for ARM/elf
        .file   "tmp.c"
        .text
        .align  2
        .global foo
        .type   foo,function
foo:
        @ Interrupt Service Routine.
        @ args = 0, pretend = 0, frame = 12
        @ frame_needed = 1, current_function_anonymous_args = 0
        mov     ip, sp
        stmfd   sp!, {r2, r3, fp, ip, lr, pc}
        sub     fp, ip, #4
        sub     sp, sp, #12
        mov     r3, #0
        str     r3, [fp, #-16]
        str     r3, [fp, #-20]
        ldr     r2, [fp, #-16]
        ldr     r3, [fp, #-20]
        add     r3, r2, r3
        str     r3, [fp, #-24]
        bl      bar
        ldmea   fp, {r2, r3, fp, sp, lr}
        subs    pc, lr, #4
.Lfe1:
        .size   foo,.Lfe1-foo

Major problem 1:
The ip register is overwritten and not restored.

Major problem 2:
The local variables overlap the pushed registers.  In this case variable a occupies the same space as the stored lr.

Major problem 3:
A function is called which has every right to alter r0 and r1, and still those registers are not saved/restored in the prologue/epilogue.

Question:
Why is the register pc stored?

If this bug is not fixed for the next gcc-3.0.x, I strongly recommend that you disable the interrupt attribute since it is unusable in its current form.

I have tried the later pre-3.1 CVS version as well, and the above bugs seem to be fixed there, but unfortunately there is another (actually much worse) showstopper there.

I will generate ASM stubs for my ISRs for now, but it would be very nice to use the interrupt attribute in the future.

/Tobias
>How-To-Repeat:
Compile the program in the Description above.  Note that no optimization is neccessary.  It may even hide the real problems.
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: