------- Comment #26 from chrbr at gcc dot gnu dot org 2010-02-01 16:30 -------
I'm afraid the unaligned access sigbug regression is another latent bug just
exhibited by the fix for the original PR :-(
what happens is the the GOT loading sequence is broken by a constant pool:
we end up to emit:
mov.l .L542,r12 (X)
bra .L516
nop
.L542:
.align 2
.long _GLOBAL_OFFSET_TABLE_
...
.L516:
mova .L545,r0 (Y) !!!!!
add r0,r12
.L545:
.long _GLOBAL_OFFSET_TABLE_
The reason for that is that the second mova instruction is unluckily now out of
range by 2 bytes. (which could happen with any other situation, even without
this patch).
IMHO We should forbid the duplication of a _GLOBAL_OFFSET_TABLE_ loading
constant while in a UNSPEC_MOVA sequence.
We should probably reduce si_limit in find_barrier when a
(set (reg:SI 0 r0)
(unspec:SI [
(const:SI (unspec:SI [
(symbol_ref ("*_GLOBAL_OFFSET_TABLE_"))
is met and next is
(set (reg:SI 12 r12)
(const:SI (unspec:SI [
(symbol_ref ("*_GLOBAL_OFFSET_TABLE_")
in PIC.
I experimenting with a couple of different solutions in this direction.
this PR was a really interesting bugs finder.... !
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42841
