https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52565
Christophe Lyon <clyon at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |INVALID
CC| |clyon at gcc dot gnu.org
Status|UNCONFIRMED |RESOLVED
--- Comment #1 from Christophe Lyon <clyon at gcc dot gnu.org> ---
(In reply to Ravaz from comment #0)
[...]
> The instruction at 0x810c forces the address used for the ldrd to be
> alligned to an 8 bytes boundary. The problem is that the double parameter is
> passed on register r2-r3 and pushed on the stack at the entry point of
> vargTest function. Since the stack is aligned on 4 bytes boundary only the
> double value may be misaligned and as a consequence the
> __builtin_va_arg(vaList, double) function fails to retrive the correct
> value.
>
> Is this a bug?
AFAIC, the ARM ABI (AAPCS) mandates that the stack is aligned on 8 bytes, so
r2/r3 are pushed on an 8 bytes boundary.
For the record, today's trunk generates (-O0):
vargTest:
@ args = 4, pretend = 16, frame = 16
@ frame_needed = 1, uses_anonymous_args = 1
@ link register save eliminated.
push {r0, r1, r2, r3}
str fp, [sp, #-4]!
add fp, sp, #0
sub sp, sp, #20
add r3, fp, #8
str r3, [fp, #-16]
ldr r3, [fp, #-16]
add r3, r3, #7
bic r3, r3, #7
add r2, r3, #8
str r2, [fp, #-16]
ldrd r2, [r3]
strd r2, [fp, #-12]
ldrd r2, [fp, #-12]
mov r0, r2
mov r1, r3
add sp, fp, #0
@ sp needed
ldr fp, [sp], #4
add sp, sp, #16
bx lr
and -O2:
vargTest:
@ args = 4, pretend = 16, frame = 8
@ frame_needed = 0, uses_anonymous_args = 1
@ link register save eliminated.
push {r0, r1, r2, r3}
sub sp, sp, #8
add r3, sp, #19
add r2, sp, #12
bic r3, r3, #7
ldrd r0, [r3]
str r2, [sp, #4]
add sp, sp, #8
@ sp needed
add sp, sp, #16
bx lr
So I think this is invalid.
