Re: [PATCH, GCC/ARM] Fix ICE when compiling empty FIQ interrupt handler in ARM mode

[Thomas Preudhomme]

Hi Christophe,

On 17/11/16 13:36, Christophe Lyon wrote:
On 16 November 2016 at 10:39, Kyrill Tkachov
<kyrylo.tkac...@foss.arm.com> wrote:

On 09/11/16 16:19, Thomas Preudhomme wrote:

Hi,

This patch fixes the following ICE when building when compiling an empty
FIQ interrupt handler in ARM mode:

empty_fiq_handler.c:5:1: error: insn does not satisfy its constraints:
 }
 ^

(insn/f 13 12 14 (set (reg/f:SI 13 sp)
        (plus:SI (reg/f:SI 11 fp)
            (const_int 4 [0x4]))) irq.c:5 4 {*arm_addsi3}
     (expr_list:REG_CFA_ADJUST_CFA (set (reg/f:SI 13 sp)
            (plus:SI (reg/f:SI 11 fp)
                (const_int 4 [0x4])))
        (nil)))

The ICE was provoked by missing an alternative to reflect that ARM mode
can do an add of general register into sp which is unpredictable in Thumb
mode add immediate.

ChangeLog entries are as follow:

*** gcc/ChangeLog ***

2016-11-04  Thomas Preud'homme  <thomas.preudho...@arm.com>

        * config/arm/arm.md (arm_addsi3): Add alternative for addition of
        general register with general register or ARM constant into SP
        register.


*** gcc/testsuite/ChangeLog ***

2016-11-04  Thomas Preud'homme  <thomas.preudho...@arm.com>

        * gcc.target/arm/empty_fiq_handler.c: New test.


Testing: bootstrapped on ARMv7-A ARM mode & testsuite shows no regression.

Is this ok for trunk?


I see that "r" does not include the stack pointer (STACK_REG is separate
from GENERAL_REGs) so we are indeed missing
that constraint.

Ok for trunk.
Thanks,
Kyrill

Best regards,

Thomas



Hi Thomas,

The new test fails when compiled with -mthumb -march=armv5t:
gcc.target/arm/empty_fiq_handler.c: In function 'fiq_handler':
gcc.target/arm/empty_fiq_handler.c:11:1: error: interrupt Service
Routines cannot be coded in Thumb mode

Right, interrupt handler can only be compiled in the mode where the CPU boots. 
So for non Thumb-only targets it should be compiled with -marm. I'll push a 
patch tomorrow.

Best regards,

Thomas