[Bug c/12084] New: 3.3.1 emitting strange stack handling code for ARM interrupts

[Bug c/12084] New: 3.3.1 emitting strange stack handling code for ARM interrupts

[jamesl at appliedminds dot com]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12084

           Summary: 3.3.1 emitting strange stack handling code for ARM
                    interrupts
           Product: gcc
           Version: 3.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jamesl at appliedminds dot com
                CC: gcc-bugs at gcc dot gnu dot org

The following was compiled with arm-elf-gcc -S -g -O2 -Wall -mcpu=arm7tdmi




void int_handler(void) __attribute__((interrupt("IRQ")));




void foo(void)


{


}




void int_handler(void)


{


    foo();


}




It emitted this assembly for int_handler:


int_handler:


.LFB5:


    .loc 1 8 0


    @ Interrupt Service Routine.


    @ args = 0, pretend = 0, frame = 0


    @ frame_needed = 1, uses_anonymous_args = 0


    str ip, [sp, #-4]!


    mov ip, sp


.LCFI0:


    stmfd   sp!, {r0, r1, r2, r3, fp, ip, lr, pc}


.LCFI1:


    sub fp, ip, #4


.LCFI2:


    .loc 1 9 0


    bl  foo


    ldmea   fp, {r0, r1, r2, r3, fp, sp, lr}


    ldmfd   sp!, {ip}


    subs    pc, lr, #4




1) The stack pointer is not being reset to its original location.


2) One of those ldm** needs a ^ after it to restore the correct CPSR.




This seems to be the same bug as in 3.2

[Bug c/12084] 3.3.1 emitting strange stack handling code for ARM interrupts

[jamesl at appliedminds dot com]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12084



------- Additional Comments From jamesl at appliedminds dot com  2003-08-28 01:12 -------
Created an attachment (id=4667)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=4667&action=view)
C file show below with bug

[Bug c/12084] 3.3.1 emitting strange stack handling code for ARM interrupts

[jamesl at appliedminds dot com]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12084



------- Additional Comments From jamesl at appliedminds dot com  2003-08-28 01:13 -------
Created an attachment (id=4668)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=4668&action=view)
Generated Assembler file from bug.c

[Bug target/12084] 3.3.1 emitting strange stack handling code for ARM interrupts

[pinskia at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12084


pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c                           |target

[Bug target/12084] 3.3.1 emitting strange stack handling code for ARM interrupts

[rearnsha at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12084


rearnsha at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


------- Additional Comments From rearnsha at gcc dot gnu dot org  2003-09-01 09:20 -------
You are incorrect on both counts:

> 1) The stack pointer is not being reset to its original location.

Yes it is.  The first ldm reloads the stack pointer with the value it when 
    mov  ip, sp
was executed.  The second ldm pops the original ip value off the stack and
restores sp to the value it had before the interrupt was taken.

> 2) One of those ldm** needs a ^ after it to restore the correct CPSR.

No.  Neither of the ldm instructions restores the PC, so it must not use ^ or
it would end up accessing the user-bank register set.   Instead, the final
subs (note use of condition flag) instruction restores the CPSR.