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Subject: target/6039: ARM interrupt attribute generats wrong code
Date: Fri, 22 Mar 2002 07:56:00 -0000	[thread overview]
Message-ID: <> (raw)

>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
>Originator:     Tobias Ringstrom
>Release:        gcc-3.0.4
Crosscompiler for arm-elf (cygwin and Linux host)
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;

gives you the following:

@ Generated by gcc 3.0.4 for ARM/elf
        .file   "tmp.c"
        .align  2
        .global foo
        .type   foo,function
        @ 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
        .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.

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.

Compile the program in the Description above.  Note that no optimization is neccessary.  It may even hide the real problems.


             reply	other threads:[~2002-03-22 15:56 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-03-22  7:56 tori [this message]
2002-04-18  9:03 mmitchel
2003-05-17  2:56 target/6039: [ARM] " Dara Hazeghi
2003-05-17  6:58 giovannibajo

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