This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: LRA has been merged into trunk.
Jakub Jelinek <jakub@redhat.com> writes:
> On Wed, Oct 24, 2012 at 10:17:48AM +0100, Richard Sandiford wrote:
>> > Sparc accepts addresses of the form:
>> >
>> > (plus:DI (lo_sum:DI (reg/f:DI 282)
>> > (symbol_ref:DI ("__mf_opts") <var_decl 0xf78d74a0 __mf_opts>))
>> > (const_int 40 [0x28]))
>> >
>> > These make use of Sparc's offsetable %lo() relocations.
>>
>> Hmm, this looks a bit risky. In terms of RTL semantics, this
>> (plus:DI ...) is a full 64-bit addition of the result of the
>> (lo_sum:DI ...), whatever that (lo_sum:DI ...) result happens to be.
>> I assume the offset is really folded into the %lo() constant itself,
>> in which case the usual form would be:
>>
>> (lo_sum:DI (reg/f:DI 282)
>> (const:DI (plus:DI (symbol_ref:DI ...) (const_int 40))))
>
> R_SPARC_OLO10 relocation has two addends though, please see
> http://sourceware.org/ml/binutils/1999-q3/msg00099.html
> so the plus there is right. The constant in second operand of PLUS
> where first operand is LO_SUM needs to be RTX_OK_FOR_OLO10_P, so that
> there is no overflow on the lo_sum operand & 0x3ff plus the
> RTX_OK_FOR_OLO10_P offset (it needs to fit into signed 13 bit field).
OK, that blasts that argument out of the water then. :-)
Richard