[RFC] combine: Handle zero_extend without subreg in change_zero_ext.
The attached patch deals with another type of zero_extend that is
not yet handled in change_zero_ext, i.e. (zero_extend
(pseudoreg)), without a "subreg" in between. What do you think?
(Mostly untested yet.)
Ciao
Dominik ^_^ ^_^
--
Dominik Vogt
IBM Germany
>From 36be099953903aa16ec1f307f0018a3e537638a5 Mon Sep 17 00:00:00 2001
From: Dominik Vogt
Date: Thu, 5 Jan 2017 17:37:37 +0100
Subject: [PATCH] combine: Handle zero_extend without subreg in
change_zero_ext.
Try replacing
(zero_extend (reg))
with
(and (subreg (reg) 0)
(const_int))
---
gcc/combine.c | 10 ++
1 file changed, 10 insertions(+)
diff --git a/gcc/combine.c b/gcc/combine.c
index e77f203..b5131b8 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -11372,6 +11372,16 @@ change_zero_ext_src (subrtx_ptr_iterator *piter)
else if (GET_CODE (x) == ZERO_EXTEND
&& SCALAR_INT_MODE_P (mode)
&& REG_P (XEXP (x, 0))
+ && !HARD_REGISTER_P (XEXP (x, 0))
+ && GET_MODE_PRECISION (GET_MODE (XEXP (x, 0)))
+ < GET_MODE_PRECISION (mode))
+{
+ /* (zero_extract (reg)) -> (and (subreg (reg) 0) (const_int)) */
+ x = gen_lowpart_SUBREG (mode, XEXP (x, 0));
+}
+ else if (GET_CODE (x) == ZERO_EXTEND
+ && SCALAR_INT_MODE_P (mode)
+ && REG_P (XEXP (x, 0))
&& HARD_REGISTER_P (XEXP (x, 0))
&& can_change_dest_mode (XEXP (x, 0), 0, mode))
{
--
2.3.0
gcc/ChangeLog-change_zero_ext-5
* combine.c (change_zero_ext_src): Handle zero_extend without subreg.
Re: [RFC] combine: Handle zero_extend without subreg in change_zero_ext.
On Thu, Jan 05, 2017 at 05:46:51PM +0100, Dominik Vogt wrote: > The attached patch deals with another type of zero_extend that is > not yet handled in change_zero_ext, i.e. (zero_extend > (pseudoreg)), without a "subreg" in between. What do you think? > (Mostly untested yet.) My main question is: where is this useful? Can you show some example please? Segher
Re: [RFC] combine: Handle zero_extend without subreg in change_zero_ext.
On Wed, Jan 11, 2017 at 12:02:40PM -0600, Segher Boessenkool wrote:
> On Thu, Jan 05, 2017 at 05:46:51PM +0100, Dominik Vogt wrote:
> > The attached patch deals with another type of zero_extend that is
> > not yet handled in change_zero_ext, i.e. (zero_extend
> > (pseudoreg)), without a "subreg" in between. What do you think?
> > (Mostly untested yet.)
>
> My main question is: where is this useful? Can you show some example
> please?
With this test program:
int foo (int *b)
{
int i;
int r;
for (i = 0; i < 77; i++)
{
r |= b[0] > 0;
r |= b[i] > 0;
}
return r;
}
before combine we have
(insn 47 45 48 7 (set (reg:SI 104)
(zero_extend:SI (reg:QI 103)))
(insn 48 47 49 7 (parallel [
(set (reg/v:SI 88 [ r ])
(ior:SI (reg/v:SI 88 [ r ])
(reg:SI 104)))
(clobber (reg:CC 33 %cc))
])
combine tries
(set (reg/v:SI 88 [ r ])
(ior:SI (zero_extend:SI (reg:QI 103))
(reg/v:SI 88 [ r ])))
With the patch it also tries
(set (reg/v:SI 88 [ r ])
(ior:SI (and:SI (subreg:SI (reg:QI 103) 0)
(const_int -1 [0x]))
(reg/v:SI 88 [ r ])))
which is just one of the standard patterns for rosbg.
Ciao
Dominik ^_^ ^_^
--
Dominik Vogt
IBM Germany
Re: [RFC] combine: Handle zero_extend without subreg in change_zero_ext.
Hi Dominik,
Thanks for the example. ROSBG, what a weird instruction.
On Thu, Jan 05, 2017 at 05:46:51PM +0100, Dominik Vogt wrote:
> --- a/gcc/combine.c
> +++ b/gcc/combine.c
> @@ -11372,6 +11372,16 @@ change_zero_ext_src (subrtx_ptr_iterator *piter)
>else if (GET_CODE (x) == ZERO_EXTEND
> && SCALAR_INT_MODE_P (mode)
> && REG_P (XEXP (x, 0))
> +&& !HARD_REGISTER_P (XEXP (x, 0))
> +&& GET_MODE_PRECISION (GET_MODE (XEXP (x, 0)))
> + < GET_MODE_PRECISION (mode))
> +{
> + /* (zero_extract (reg)) -> (and (subreg (reg) 0) (const_int)) */
s/zero_extract/zero_extend/
> * combine.c (change_zero_ext_src): Handle zero_extend without subreg.
"Handle zero_extend of a pseudo."?
Okay for trunk with that. Thanks for the patch,
Segher
Re: [RFC] combine: Handle zero_extend without subreg in change_zero_ext.
On Thu, Jan 12, 2017 at 11:02:36AM -0600, Segher Boessenkool wrote:
> Hi Dominik,
>
> Thanks for the example. ROSBG, what a weird instruction.
>
> On Thu, Jan 05, 2017 at 05:46:51PM +0100, Dominik Vogt wrote:
> > --- a/gcc/combine.c
> > +++ b/gcc/combine.c
> > @@ -11372,6 +11372,16 @@ change_zero_ext_src (subrtx_ptr_iterator *piter)
> >else if (GET_CODE (x) == ZERO_EXTEND
> >&& SCALAR_INT_MODE_P (mode)
> >&& REG_P (XEXP (x, 0))
> > + && !HARD_REGISTER_P (XEXP (x, 0))
> > + && GET_MODE_PRECISION (GET_MODE (XEXP (x, 0)))
> > + < GET_MODE_PRECISION (mode))
> > +{
> > + /* (zero_extract (reg)) -> (and (subreg (reg) 0) (const_int)) */
>
> s/zero_extract/zero_extend/
>
> > * combine.c (change_zero_ext_src): Handle zero_extend without subreg.
>
> "Handle zero_extend of a pseudo."?
k
> Okay for trunk with that.
It still needs testing. I'll do that in a while.
Ciao
Dominik ^_^ ^_^
--
Dominik Vogt
IBM Germany
Re: [RFC] combine: Handle zero_extend without subreg in change_zero_ext.
On Thu, Jan 12, 2017 at 11:02:36AM -0600, Segher Boessenkool wrote:
> Thanks for the example. ROSBG, what a weird instruction.
And it's annoying too because it does the same as RISBG in some
cases and can confuse "combine" to take a different branch that
turns out to be a dead end.
> On Thu, Jan 05, 2017 at 05:46:51PM +0100, Dominik Vogt wrote:
> > --- a/gcc/combine.c
> > +++ b/gcc/combine.c
> > @@ -11372,6 +11372,16 @@ change_zero_ext_src (subrtx_ptr_iterator *piter)
> >else if (GET_CODE (x) == ZERO_EXTEND
> >&& SCALAR_INT_MODE_P (mode)
> >&& REG_P (XEXP (x, 0))
> > + && !HARD_REGISTER_P (XEXP (x, 0))
> > + && GET_MODE_PRECISION (GET_MODE (XEXP (x, 0)))
> > + < GET_MODE_PRECISION (mode))
> > +{
> > + /* (zero_extract (reg)) -> (and (subreg (reg) 0) (const_int)) */
>
> s/zero_extract/zero_extend/
>
> > * combine.c (change_zero_ext_src): Handle zero_extend without subreg.
>
> "Handle zero_extend of a pseudo."?
>
> Okay for trunk with that. Thanks for the patch,
The patch forgot to set "size" and generated invalid Rtl because
of that. Fixed and tested, but I'd prefer to repost my growing
stack of patches when gcc-7 is released. There are too many
changes in "combine" and "simplify" that may depend on each other.
Ciao
Dominik ^_^ ^_^
--
Dominik Vogt
IBM Germany
