On 18/01/14 20:11, pins...@gmail.com wrote:
On Jan 18, 2014, at 12:04 PM, "Paulo J. Matos" <pa...@matos-sorge.com> wrote:
On 17/01/14 17:36, Eric Botcazou wrote:
I am not implying that this is a GCC bug, unless you think
WORD_REISTER_OPERATIONS should have avoided the creation of such
paradoxical subreg.
No, that's precisely the contrary, WORD_REGISTER_OPERATIONS tends to create
paradoxical subregs.
I might then, be misunderstanding the reason to enable
WORD_REGISTER_OPERATIONS. From the documentation:
"Macro: WORD_REGISTER_OPERATIONS
Define this macro if operations between registers with integral mode smaller
than a word are always performed on the entire register. Most RISC machines have
this property and most CISC machines do not. "
The machine I am targeting is a 64bit vector machine. When you perform a 16 bit
operation, the whole register is changed because the operation actually changes
every 16bit group of the register. So it seems I should enable
WORD_REGISTER_OPERATIONS.
As an aside, is there any machine in gcc mainline like this?
Yes spu. It is a 128bit vector machine, operations happen in that size and
compares are done in the same size.
Thanks for the reference.
I think you misunderstood WORD_REGISTER_OPERATIONS, it means the operation
happens on the whole register in that a 16bit add is the same as a 32bit one.
Oh... my... you're right. If I now read the doc for
WORD_REGISTER_OPERATIONS what you're saying makes sense. I shouldn't
have it enabled.
Thanks for your help.
Paulo Matos
Thanks,
Andrew Pinski
--
PMatos
