[Bug c/16634] New: arm-elf-gcc 3.4.0 problems when generating code for __attribute__ ((interrupt ("IRQ")))

[Bug c/16634] New: arm-elf-gcc 3.4.0 problems when generating code for __attribute__ ((interrupt ("IRQ")))

[bob at cnxtech dot com]

The gcc 3.4.0 still have problems on generating the entry/exit code for
interrupts, if we supress the "apcs-frame" option. When the code is compiled
with "-mno-apcs-frame" the entry code subtracts 4 from the "lr" before pushing
it into stack, and do it again on the exit code.

__attribute__ ((interrupt ("IRQ"))) void int_handler(void)
{
	foo();
}
 
arm-elf-gcc -mcpu=arm7tdmi -mno-apcs-frame -mthumb-interwork -Wall -O2 -c test.c
00000000 <int_handler>:
   0:   e24ee004        sub     lr, lr, #4      ; 0x4
   4:   e92d500f        stmdb   sp!, {r0, r1, r2, r3, ip, lr}
   8:   ebfffffe        bl      0 <int_handler>
   c:   e8bd500f        ldmia   sp!, {r0, r1, r2, r3, ip, lr}
  10:   e25ef004        subs    pc, lr, #4      ; 0x4


arm-elf-gcc -mcpu=arm7tdmi -mapcs-frame -mthumb-interwork -Wall -O2 -c test.c
00000000 <int_handler>:
   0:   e52dc004        str     ip, [sp, -#4]!
   4:   e1a0c00d        mov     ip, sp
   8:   e92dd80f        stmdb   sp!, {r0, r1, r2, r3, fp, ip, lr, pc}
   c:   e24cb004        sub     fp, ip, #4      ; 0x4
  10:   ebfffffe        bl      0 <int_handler>
  14:   e89d680f        ldmia   sp, {r0, r1, r2, r3, fp, sp, lr}
  18:   e8bd1000        ldmia   sp!, {ip}
  1c:   e25ef004        subs    pc, lr, #4      ; 0x4

-- 
           Summary: arm-elf-gcc 3.4.0 problems when generating code for
                    __attribute__ ((interrupt ("IRQ")))
           Product: gcc
           Version: 3.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: bob at cnxtech dot com
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: i686-pc-cygwin
GCC target triplet: arm-elf-gcc


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16634

[Bug target/16634] arm-elf-gcc 3.4.0 problems when generating code for __attribute__ ((interrupt ("IRQ")))

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c                           |target
           Keywords|                            |wrong-code


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16634

[Bug target/16634] arm-elf-gcc problems when generating code for __attribute__ ((interrupt ("IRQ")))

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|arm-elf-gcc 3.4.0 problems  |arm-elf-gcc problems when
                   |when generating code for    |generating code for
                   |__attribute__ ((interrupt   |__attribute__ ((interrupt
                   |("IRQ")))                   |("IRQ")))


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16634

[Bug target/16634] arm-elf-gcc problems when generating code for __attribute__ ((interrupt ("IRQ")))

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   GCC host triplet|i686-pc-cygwin              |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16634

[Bug target/16634] arm-elf-gcc problems when generating code for __attribute__ ((interrupt ("IRQ")))

[pbrook at gcc dot gnu dot org]

------- Comment #1 from pbrook at gcc dot gnu dot org  2006-08-08 23:05 -------
*** Bug 25428 has been marked as a duplicate of this bug. ***


-- 

pbrook at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |th dot r dot klein at web
                   |                            |dot de


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16634

[Bug target/16634] arm-elf-gcc problems when generating code for __attribute__ ((interrupt ("IRQ")))

[pbrook at gcc dot gnu dot org]

------- Comment #2 from pbrook at gcc dot gnu dot org  2006-08-08 23:47 -------
Patch here:
http://gcc.gnu.org/ml/gcc-patches/2006-08/msg00230.html


-- 

pbrook at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2006-08-08 23:47:42
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16634

[Bug target/16634] arm-elf-gcc problems when generating code for __attribute__ ((interrupt ("IRQ")))

[rearnsha at gcc dot gnu dot org]

------- Comment #3 from rearnsha at gcc dot gnu dot org  2006-09-11 10:41 -------
*** Bug 29004 has been marked as a duplicate of this bug. ***


-- 

rearnsha at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |hans dot buchmann at fhso
                   |                            |dot ch


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16634

[Bug target/16634] arm-elf-gcc problems when generating code for __attribute__ ((interrupt ("IRQ")))

[tbm at cyrius dot com]

------- Comment #4 from tbm at cyrius dot com  2006-09-11 11:31 -------
(In reply to comment #2)
> Patch here:
> http://gcc.gnu.org/ml/gcc-patches/2006-08/msg00230.html

What's the status of this patch?


-- 

tbm at cyrius dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rearnsha at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16634

[Bug target/16634] arm-elf-gcc problems when generating code for __attribute__ ((interrupt ("IRQ")))

[tla at thrane dot com]

------- Comment #5 from tla at thrane dot com  2006-11-14 16:28 -------
(In reply to comment #4)
> What's the status of this patch?

The bug is also present in arm-elf-gcc version 4.1.0
However, adding the -fno-omit-frame-pointer parameter, make
the compiler emit the correct code in the mentioned code example.


-- 

tla at thrane dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tla at thrane dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16634

[Bug target/16634] arm-elf-gcc problems when generating code for __attribute__ ((interrupt ("IRQ")))

[pbrook at gcc dot gnu dot org]

------- Comment #6 from pbrook at gcc dot gnu dot org  2007-01-04 00:09 -------
Subject: Bug 16634

Author: pbrook
Date: Thu Jan  4 00:09:48 2007
New Revision: 120413

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=120413
Log:
2007-01-03  Paul Brook  <paul@codesourcery.com>

        PR target/16634
        gcc/
        * config/arm/arm.c (output_return_instruction): Pop PC in interrupt
        functions.
        (use_return_insn): Return 0 for Thumb interrupt functions.
        (print_multi_reg): Add rfe argument for IRQ returns.
        (arm_output_epilogue): Pop interrupt return address directly into PC.
        (arm_expand_prologue): Only adjust IRQ return address in Arm mode.


Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/arm/arm.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16634

[Bug target/16634] arm-elf-gcc problems when generating code for __attribute__ ((interrupt ("IRQ")))

[david+gcc at porkrind dot org]

------- Comment #7 from david+gcc at porkrind dot org  2007-05-03 03:14 -------
This still fails in gcc 4.1.2 under certain conditions. I can provide a test
case if necessary.


-- 

david+gcc at porkrind dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |david+gcc at porkrind dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16634

[Bug target/16634] arm-elf-gcc problems when generating code for __attribute__ ((interrupt ("IRQ")))

[sgh at sgh dot dk]

------- Comment #8 from sgh at sgh dot dk  2007-08-06 09:08 -------
also fails on 4.2.1


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sgh at sgh dot dk changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sgh at sgh dot dk


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16634

[Bug target/16634] arm-elf-gcc problems when generating code for __attribute__ ((interrupt ("IRQ")))

[ralf dot guetlein at web dot de]

------- Comment #9 from ralf dot guetlein at web dot de  2007-11-08 21:42 -------
(In reply to comment #8)
> also fails on 4.2.1

is this bug still present in 4.2.2?

Acc. to my obervations the error only shows up when not all auto variables can
be mapped to registers, and additional variables are located on stack. As a
work-around, if a more complex interrupt handler is needed, place the code in a
subfunction and call this function from the interrupt handler. In this case no
stack is reserved in the interrupt handler, and the generated code is OK. Care
must be taken, of course, that the optimizer does not inline the code for
IntFunc().

Example:
void IntFunc(void);

__attribute__((interrupt("IRQ")) void IntHandler(void)
{
  IntFunc();
}

__attribute__(noinline)) void IntFunc(void)
{
  // interrupt code here!
}


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16634

[Bug target/16634] arm-elf-gcc problems when generating code for __attribute__ ((interrupt ("IRQ")))

[mmz at gmx dot net]

------- Comment #10 from mmz at gmx dot net  2008-02-07 13:54 -------
(In reply to comment #9)
> is this bug still present in 4.2.2?

I can confirm this bug still exists in 4.2.2 and 4.2.3.

> Acc. to my obervations the error only shows up when not all auto variables can
> be mapped to registers, and additional variables are located on stack. As a
> work-around, if a more complex interrupt handler is needed, place the code in a
> subfunction and call this function from the interrupt handler. In this case no
> stack is reserved in the interrupt handler, and the generated code is OK. Care
> must be taken, of course, that the optimizer does not inline the code for
> IntFunc().

Your subfunction workaround actually did the trick. The generated return
instruction is "ldm sp!, {r0, r1, r2, r3, ip, pc}^". However, if a more complex
interrupt handler is implemented the wrong return instruction generated. The
results seem a bit unpredictable so I currently use plain assembler for my
interrupts.

Example:
extern __attribute__ ((interrupt ("IRQ"))) void
base_int_ctrl_top_irq_handler(void)
{
    int_ctrl_status_t status;

    status.val = READ_REG_U32(ADDR_STATUS_NIRQ);

    if (status.bf.x) {
        puts("Spurious x IRQ!");
    } else if (status.bf.y) {
        puts("Spurious y IRQ!");
    } else if (status.bf.timer) {
        base_timer_interrupt();
    } else if (status.bf.z) {
        puts("Spurious z IRQ!");
    } else {
        puts("Spurious unknown IRQ!");
    }
}

Generated assembly for return:
pop     {r0, r1, r2, r3, ip, lr}
subs    pc, lr, #4      ; 0x4
(and lr was already decremented by 4 when the handler was entered)

So your observations are correct.

Bug #27859 seems to be a duplicate of this bug and contains a patch. However,
this patch is probably not optimal since it just replaces the final "subs" by a
"movs" while the best solution seems to be the "ldmfd ..." instruction above.


-- 

mmz at gmx dot net changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mmz at gmx dot net


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16634

[Bug target/16634] arm-elf-gcc problems when generating code for __attribute__ ((interrupt ("IRQ")))

[sgh at sgh dot dk]

------- Comment #11 from sgh at sgh dot dk  2009-02-12 21:58 -------
Since this is not marked to be fixes I assume is hasn't been fixed in 4.3.3.
Wat is wrong with Pauls patch since it hasn't been included ?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16634

[Bug target/16634] arm-elf-gcc problems when generating code for __attribute__ ((interrupt ("IRQ")))

[ramana at gcc dot gnu dot org]

------- Comment #12 from ramana at gcc dot gnu dot org  2010-01-09 23:27 -------
The code generated on trunk, 4.4 and 4.3 with arm-eabi-gcc at O2 for the test
in Comment #0 is 

int_handler:
        @ Interrupt Service Routine.
        @ args = 0, pretend = 0, frame = 0
        @ frame_needed = 0, uses_anonymous_args = 0
        sub     lr, lr, #4
        stmfd   sp!, {r0, r1, r2, r3, ip, lr}
        bl      foo
        ldmfd   sp!, {r0, r1, r2, r3, ip, pc}^

which appears to be the expected code generated. 


This appears to be fixed. If there is a problem please open a separate bug
report. I tried the testcase in Comment #10 but that doesn't even compile .
Attempting to reverse create a testcase using similar structs didn't show the
problem. 


-- 

ramana at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
           Priority|P2                          |P4
         Resolution|                            |FIXED
   Target Milestone|---                         |4.3.5


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16634