Re: [RFC PATCH, i386]: Prefer %ebx in set_got patterns
On Mon, Dec 1, 2014 at 6:47 PM, Jeff Law wrote:
> On 11/27/14 04:19, Uros Bizjak wrote:
>> Attached patch helps RA to choose the most appropriate PIC register by
>> changing the register preference for set_got patterns. Using this
>> patch, there should really be a reason for RA to avoid ABI mandated
>> hard PIC reg.
>
> Agreed.
>
>>
>> This patch avoids many mov %exx,%ebx in front of the calls, that
>> happen with unpatched compiler even with Vladimir's latest RA patch to
>> avoid duplicated PIC registers.
>
> [ ... ]
> Far more than I would have expected.
>
>
>> 2014-11-27 Uros Bizjak
>>
>> * config/i386/i386.md (set_got): Use "=b,?r" constraint for operand
>> 0.
>> (set_got_labelled): Ditto.
>> (set_got_rex64): Ditto.
>> (set_rip_rex64): Ditto.
>> (set_got_offset_rex64): Ditto.
>>
>> Bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.
>>
>> Thoughts?
>
> As HJ mentioned, it's not perfect, but it's certainly better than what we're
> doing now.
>
> The only thing I don't like is that it's really disguising failings in
> IRA/LRA.
Yes, this is the reason I have second thoughts about the patch. I
think that it papers over real issue in RA.
> Can you file a bug for that issue so that Vlad can track it.
Actually, I noticed it in libgo, where searching for various non-bx
thunks reveals many cases. I don't have a small testcase at hand ATM.
Uros.
Re: [RFC PATCH, i386]: Prefer %ebx in set_got patterns
On Mon, Dec 01, 2014 at 10:47:40AM -0700, Jeff Law wrote:
> > * config/i386/i386.md (set_got): Use "=b,?r" constraint for operand 0.
> > (set_got_labelled): Ditto.
> > (set_got_rex64): Ditto.
> > (set_rip_rex64): Ditto.
> > (set_got_offset_rex64): Ditto.
> >
> >Bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.
> >
> >Thoughts?
> As HJ mentioned, it's not perfect, but it's certainly better than what we're
> doing now.
>
> The only thing I don't like is that it's really disguising failings in
> IRA/LRA.
As HJ mentioned, it should be done for 32-bit patterns only, at least for
now, there is no class for the r15 register.
Jakub
Re: [RFC PATCH, i386]: Prefer %ebx in set_got patterns
On 11/27/14 04:19, Uros Bizjak wrote:
Hello!
Attached patch helps RA to choose the most appropriate PIC register by
changing the register preference for set_got patterns. Using this
patch, there should really be a reason for RA to avoid ABI mandated
hard PIC reg.
Agreed.
This patch avoids many mov %exx,%ebx in front of the calls, that
happen with unpatched compiler even with Vladimir's latest RA patch to
avoid duplicated PIC registers.
[ ... ]
Far more than I would have expected.
2014-11-27 Uros Bizjak
* config/i386/i386.md (set_got): Use "=b,?r" constraint for operand 0.
(set_got_labelled): Ditto.
(set_got_rex64): Ditto.
(set_rip_rex64): Ditto.
(set_got_offset_rex64): Ditto.
Bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.
Thoughts?
As HJ mentioned, it's not perfect, but it's certainly better than what
we're doing now.
The only thing I don't like is that it's really disguising failings in
IRA/LRA.
Can you file a bug for that issue so that Vlad can track it.
jeff
Re: [RFC PATCH, i386]: Prefer %ebx in set_got patterns
On Thu, Nov 27, 2014 at 3:19 AM, Uros Bizjak wrote:
> Hello!
>
> Attached patch helps RA to choose the most appropriate PIC register by
> changing the register preference for set_got patterns. Using this
> patch, there should really be a reason for RA to avoid ABI mandated
> hard PIC reg.
>
> This patch avoids many mov %exx,%ebx in front of the calls, that
> happen with unpatched compiler even with Vladimir's latest RA patch to
> avoid duplicated PIC registers.
>
> As a smoke test, I have checked 32bit libgo.so.6.0.0 library, where now we
> have:
>
> [uros@omen7 .libs]$ grep thunk.bx aaa | wc -l
> 7693
> [uros@omen7 .libs]$ grep thunk.ax aaa | wc -l
> 10
> [uros@omen7 .libs]$ grep thunk.cx aaa | wc -l
> 4
> [uros@omen7 .libs]$ grep thunk.dx aaa | wc -l
> 8
> [uros@omen7 .libs]$ grep thunk.bp aaa | wc -l
> 497
> [uros@omen7 .libs]$ grep thunk.si aaa | wc -l
> 145
> [uros@omen7 .libs]$ grep thunk.di aaa | wc -l
> 198
>
> 2014-11-27 Uros Bizjak
>
> * config/i386/i386.md (set_got): Use "=b,?r" constraint for operand 0.
EBX is needed only if PLT is used. If PLT isn't used, we should try
caller saved registers first.
> (set_got_labelled): Ditto.
> (set_got_rex64): Ditto.
> (set_rip_rex64): Ditto.
> (set_got_offset_rex64): Ditto.
We shouldn't do it for 64-bit.
> Bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.
>
> Thoughts?
>
> Uros
--
H.J.
[RFC PATCH, i386]: Prefer %ebx in set_got patterns
Hello!
Attached patch helps RA to choose the most appropriate PIC register by
changing the register preference for set_got patterns. Using this
patch, there should really be a reason for RA to avoid ABI mandated
hard PIC reg.
This patch avoids many mov %exx,%ebx in front of the calls, that
happen with unpatched compiler even with Vladimir's latest RA patch to
avoid duplicated PIC registers.
As a smoke test, I have checked 32bit libgo.so.6.0.0 library, where now we have:
[uros@omen7 .libs]$ grep thunk.bx aaa | wc -l
7693
[uros@omen7 .libs]$ grep thunk.ax aaa | wc -l
10
[uros@omen7 .libs]$ grep thunk.cx aaa | wc -l
4
[uros@omen7 .libs]$ grep thunk.dx aaa | wc -l
8
[uros@omen7 .libs]$ grep thunk.bp aaa | wc -l
497
[uros@omen7 .libs]$ grep thunk.si aaa | wc -l
145
[uros@omen7 .libs]$ grep thunk.di aaa | wc -l
198
2014-11-27 Uros Bizjak
* config/i386/i386.md (set_got): Use "=b,?r" constraint for operand 0.
(set_got_labelled): Ditto.
(set_got_rex64): Ditto.
(set_rip_rex64): Ditto.
(set_got_offset_rex64): Ditto.
Bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.
Thoughts?
Uros
Index: config/i386/i386.md
===
--- config/i386/i386.md (revision 218111)
+++ config/i386/i386.md (working copy)
@@ -12101,7 +12101,7 @@
"ix86_expand_prologue (); DONE;")
(define_insn "set_got"
- [(set (match_operand:SI 0 "register_operand" "=r")
+ [(set (match_operand:SI 0 "register_operand" "=b,?r")
(unspec:SI [(const_int 0)] UNSPEC_SET_GOT))
(clobber (reg:CC FLAGS_REG))]
"!TARGET_64BIT"
@@ -12110,7 +12110,7 @@
(set_attr "length" "12")])
(define_insn "set_got_labelled"
- [(set (match_operand:SI 0 "register_operand" "=r")
+ [(set (match_operand:SI 0 "register_operand" "=b,?r")
(unspec:SI [(label_ref (match_operand 1))]
UNSPEC_SET_GOT))
(clobber (reg:CC FLAGS_REG))]
@@ -12120,7 +12120,7 @@
(set_attr "length" "12")])
(define_insn "set_got_rex64"
- [(set (match_operand:DI 0 "register_operand" "=r")
+ [(set (match_operand:DI 0 "register_operand" "=b,?r")
(unspec:DI [(const_int 0)] UNSPEC_SET_GOT))]
"TARGET_64BIT"
"lea{q}\t{_GLOBAL_OFFSET_TABLE_(%%rip), %0|%0, _GLOBAL_OFFSET_TABLE_[rip]}"
@@ -12129,7 +12129,7 @@
(set_attr "mode" "DI")])
(define_insn "set_rip_rex64"
- [(set (match_operand:DI 0 "register_operand" "=r")
+ [(set (match_operand:DI 0 "register_operand" "=b,?r")
(unspec:DI [(label_ref (match_operand 1))] UNSPEC_SET_RIP))]
"TARGET_64BIT"
"lea{q}\t{%l1(%%rip), %0|%0, %l1[rip]}"
@@ -12138,7 +12138,7 @@
(set_attr "mode" "DI")])
(define_insn "set_got_offset_rex64"
- [(set (match_operand:DI 0 "register_operand" "=r")
+ [(set (match_operand:DI 0 "register_operand" "=b,?r")
(unspec:DI
[(label_ref (match_operand 1))]
UNSPEC_SET_GOT_OFFSET))]
