Re: [PATCH] Expand PIC calls without PLT with -fno-plt

[Jeff Law <law@redhat.com>]

On 05/04/2015 11:39 AM, Jakub Jelinek wrote:
> On Mon, May 04, 2015 at 11:34:05AM -0600, Jeff Law wrote:
>> On 05/04/2015 10:37 AM, Alexander Monakov wrote:
>>> This patch introduces option -fno-plt that allows to expand calls that would
>>> go via PLT to load the address of the function immediately at call site (which
>>> introduces a GOT load).  Cover letter explains the motivation for this patch.
>>>
>>> New option documentation for invoke.texi is missing from the patch; if this is
>>> accepted I'll be happy to send a v2 with documentation added.
>>>
>>> 	* calls.c (prepare_call_address): Transform PLT call to GOT lookup and
>>> 	indirect call by forcing address into a pseudo with -fno-plt.
>>> 	* common.opt (flag_plt): New option.
>> OK once you cobble together the invoke.texi changes.
>
> Isn't what Michael/Alan suggested better?  I mean as/ld/compiler changes to
> inline the plt slot's first part, then lazy binding will work fine.
I must have missed Alan/Michael's message.

ISTM the win here is that by going through the GOT, you can CSE the GOT 
reference and possibly get some more register allocation freedom.  Is 
that still the case with Alan/Michael's approach?

jeff