[Bug target/44888] New: Stack pointer corruption within interrupt routine when compiled with -Os

["rob dot thornburrow at adder dot com" <gcc-bugzilla@gcc.gnu.org>]

# 1 "irq.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "irq.c"

extern void add_irq(int, void (*irq)(void));
extern void do_something(void);

static __attribute__ ((interrupt("IRQ"))) void irq(void)
{
    unsigned long ints;

    ints = (*(volatile unsigned long *)(0x00000000));
    ints &= ~(*(volatile unsigned long *)(0x00000004));

    if (ints & 0x1)
        do_something();

    (*(volatile unsigned long *)(0x00000000)) = ints;
}

void init(void)
{
    add_irq(0, irq);
}


When compiled with -Os using gcc 4.5.0 (arm-none-eabi), the generated assembly
for irq() subtracts 4 from the stack pointer immediately prior to calling
do_something() but never adds 4 back before the function exits.  This results
in the program counter (and all registers saved at the start of the function)
being loaded with incorrect values.

This doesn't happen with 4.5.0 when compiled with no optimisation (-O0) or with
4.4.2 (arm-elf) with any optimisation level.

It appears to only be a problem when the function is defined as an interrupt
handler as when defined as a normal function (with standard entry/exit
wrappers) the generated assembly looks correct.

Target: arm-none-eabi
Configured with: ../gcc-4.5.0/configure --target=arm-none-eabi
--prefix=/home/ya
garto/install --disable-nls --disable-shared --disable-threads --with-gcc
--with
-gnu-ld --with-gnu-as --with-dwarf2 --enable-languages=c,c++ --enable-interwork
--enable-multilib --with-newlib
--with-headers=../newlib-1.18.0/newlib/libc/incl
ude --disable-libssp --disable-libstdcxx-pch --disable-libmudflap
--disable-libg
omp -v
Thread model: single
gcc version 4.5.0 (GCC)
COLLECT_GCC_OPTIONS='-mcpu=arm7tdmi-s' '-std=gnu99' '-Wall' '-c' '-fno-common'
'-Os' '-o'


-- 
           Summary: Stack pointer corruption within interrupt routine when
                    compiled with -Os
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rob dot thornburrow at adder dot com
GCC target triplet: arm-none-eabi


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44888