[Bug rtl-optimization/43471] Unnecessary reload of asm "m" operand address

[mirq-gccboogs at rere dot qmqm dot pl]

------- Comment #2 from mirq-gccboogs at rere dot qmqm dot pl  2010-03-23 05:43 
-------
Hmm. I must have missed something while cutting down the test case as this
simple example works now...

Here is bigger test that might be related:

code:

struct a {
        int f1, f2;
};

struct b {
        unsigned f3;
        struct a s1, s2;
};

register struct b *const reg asm("r4");

static int diff(struct a *ptr)
{
        return ptr->f1 > ptr->f2 ? ptr->f1 - ptr->f2 : 100 - ptr->f1;
}

void c(void);

void d(void)
{
        while (diff(&reg->s2))
                c();
}

compiles to:

d:
        @ args = 0, pretend = 0, frame = 0
        @ frame_needed = 0, uses_anonymous_args = 0
        push    {r5, lr}
        mov     r5, r4
        b       .L2
.L5:   
        bl      c
.L2:   
        ldr     r3, [r5, #12]
        ldr     r1, [r5, #16]
        rsb     r2, r3, #100
        cmp     r3, r1
        it      gt
        subgt   r2, r3, r1
        cmp     r2, #0
        bne     .L5
        pop     {r5, pc}

with:

arm-none-eabi-gcc -mcpu=cortex-m3 -mthumb -O3 -S a.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43471