https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111500
--- Comment #2 from Luke <gnu.arne at wgboome dot org> ---
(In reply to Andrew Pinski from comment #1)
> Can you attach (compilible) examples code for each issue? Really these
> should be filed seperately too.
do u mean, i should file 3 further bug reports?
i try examples for artifact #1 first...
is it right like this?
example code for artifact #1a:
// "cmp" follows the "subs" immediately
__attribute((noinline)) void artiSUBS() {
for (int i=100; i>0; i--)
200017ec: 2364 movs r3, #100 ; 0x64
*(volatile int*)0xE000E014 = i;
200017ee: 4a03 ldr r2, [pc, #12] ; (200017fc)
200017f0: 6013 str r3, [r2, #0]
for (int i=100; i>0; i--)
200017f2: 3b01 subs r3, #1
200017f4: 2b00 cmp r3, #0
200017f6: d1fb bne.n 200017f0
}
200017f8: 4770 bx lr
200017fa: 46c0 nop
200017fc: e000e014
example code for artifact #1b:
// gcc tends to do the "i--" too early; "ldr" does not touch flags
// maybe because it hopes to get beneficial pipeline effects at loop entry?
__attribute((noinline)) void artiSUBS() {
200017ec: 2364 movs r3, #100 ; 0x64
for (int i=100; i>0; i--)
(void) *(volatile int*)0xE000E014;
200017ee: 4a03 ldr r2, [pc, #12] ; (200017fc)
200017f0: 3b01 subs r3, #1
200017f2: 6811 ldr r1, [r2, #0]
for (int i=100; i>0; i--)
200017f4: 2b00 cmp r3, #0
200017f6: d1fb bne.n 200017f0
}
200017f8: 4770 bx lr
200017fa: 46c0 nop
200017fc: e000e014
