From: Richard Biener <richard.guenther@gmail.com>
To: Kugan <kugan.vivekanandarajah@linaro.org>
Cc: Jakub Jelinek <jakub@redhat.com>,
"gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH 2/2] Enable elimination of zext/sext
Date: Tue, 05 Aug 2014 14:18:00 -0000 [thread overview]
Message-ID: <CAFiYyc1Gh6teQWgc44j+U1w8S6oyXHigPj8N0-MqTOVg1Xbn5Q@mail.gmail.com> (raw)
In-Reply-To: <53DBBA6B.3070507@linaro.org>
On Fri, Aug 1, 2014 at 6:03 PM, Kugan <kugan.vivekanandarajah@linaro.org> wrote:
>>>> if (rhs_uns)
>>>> return wi::ge_p (min, 0); // if min >= 0 then range contains positive values
>>>> else
>>>> return wi::le_p (max, wi::max_value (TYPE_PRECISION (TREE_TYPE
>>>> (ssa)), SIGNED); // if max <= signed-max-of-type then range doesn't
>>>> need sign-extension
>>>
>>> I think we will have to check that ssa has necessary sign/zero extension
>>> when assigned to lhs_type. If PROMOTE_MODE tells us that ssa's type will
>>> be interpreted differently, the value range of ssa also will have
>>> corresponding range. In this cases, shouldn’t we have to check for
>>> upper and lower limit for both min and max?
>>
>> Hmm? That's exactly what the check is testing... we know that
>> min <= max thus if min >= 0 then max >= 0.
>>
>> zero_extension will never do anything on [0, INF]
>>
>> If max < MAX-SIGNED then sign-extension will not do anything. Ok,
>> sign-extension will do sth for negative values still. So rather
>>
>> if (rhs_uns)
>> return wi::geu_p (min, 0);
>> else
>> return wi::ges_p (min, 0) && wi::les_p (max, wi::max_value
>> (TYPE_PRECISION (TREE_TYPE (ssa)), SIGNED));
>>
>> ?
>
> Thanks for the explanation. I agree. Don’t we have to however check this
> on lhs_uns as this function is checking if ssa is promoted for lhs_sign
> and lhs_mode?
>
> Here is an attempt based on this. I ran regression testing with
> arm-none-linux-gnueabi on qemu-arm without any new regressions.
>
> Sine I am not comparing value ranges to see if it can be represented in
> lhs_sigh, I can now skip the PROMOTED_MODE check.
Now I'm lost. You call this function from two contexts:
diff --git a/gcc/calls.c b/gcc/calls.c
index a3e6faa..eac512f 100644
--- a/gcc/calls.c
+++ b/gcc/calls.c
@@ -1484,7 +1484,10 @@ precompute_arguments (int num_actuals, struct
arg_data *args)
args[i].initial_value
= gen_lowpart_SUBREG (mode, args[i].value);
SUBREG_PROMOTED_VAR_P (args[i].initial_value) = 1;
- SUBREG_PROMOTED_SET (args[i].initial_value, args[i].unsignedp);
+ if (is_promoted_for_type (args[i].tree_value, mode,
!args[i].unsignedp))
+ SUBREG_PROMOTED_SET (args[i].initial_value,
SRP_SIGNED_AND_UNSIGNED);
+ else
+ SUBREG_PROMOTED_SET (args[i].initial_value, args[i].unsignedp);
and
@@ -9527,7 +9587,10 @@ expand_expr_real_1 (tree exp, rtx target, enum
machine_mode tmode,
temp = gen_lowpart_SUBREG (mode, decl_rtl);
SUBREG_PROMOTED_VAR_P (temp) = 1;
- SUBREG_PROMOTED_SET (temp, unsignedp);
+ if (is_promoted_for_type (ssa_name, mode, !unsignedp))
+ SUBREG_PROMOTED_SET (temp, SRP_SIGNED_AND_UNSIGNED);
+ else
+ SUBREG_PROMOTED_SET (temp, unsignedp);
return temp;
}
what's the semantic of setting SRP_SIGNED_AND_UNSIGNED
on the subreg? That is, for the created (subreg:lhs_mode
(reg:<PROMOTE_MODE of ssa> N))?
it seems that we need to verify that 'ssa', when promoted,
does not have bits set above the target modes MSB when
we know it is zero-extended (according to PROMOTE_MODE)?
Or has all bits set to one and is sign-extended (according to
PROMOTE_MODE)?
Now it seems that the promotion is according to
promote_{function,decl}_mode in expand_expr_real_1
and according to promote_mode in calls.c.
The function comment above promoted_for_type_p needs to be
more elaborate on what invariant it checks. As you pass in
the subreg mode but you need to verify the larger mode is
properly extended.
> I am still using wide_int::from (instead of wi::max_value) to get the
> limit as I have to match the precision with min, max precision.
> otherwise wide_int comparisons will not work. Is there a better way for
> this?
I don't understand. wi::max_value takes a precision argument.
>
> /* Return TRUE if value in SSA is already zero/sign extended for lhs type
> (type here is the combination of LHS_MODE and LHS_UNS) using value range
> information stored. Return FALSE otherwise. */
> bool
> promoted_for_type_p (tree ssa, enum machine_mode lhs_mode, bool lhs_uns)
> {
> wide_int min, max, limit;
> tree lhs_type;
> bool rhs_uns;
> signop rhs_signop;
>
> if (ssa == NULL_TREE
> || TREE_CODE (ssa) != SSA_NAME
> || !INTEGRAL_TYPE_P (TREE_TYPE (ssa)))
> return false;
>
> /* Return FALSE if value_range is not recorded for SSA. */
> if (get_range_info (ssa, &min, &max) != VR_RANGE)
> return false;
>
> rhs_uns = TYPE_UNSIGNED (TREE_TYPE (ssa));
> rhs_signop = rhs_uns ? UNSIGNED : SIGNED;
> lhs_type = lang_hooks.types.type_for_mode (lhs_mode, lhs_uns);
> limit = wide_int::from (TYPE_MAX_VALUE (lhs_type),
> TYPE_PRECISION (TREE_TYPE (ssa)), SIGNED);
>
> if (lhs_uns)
> /* If min >= 0 then range contains positive values and doesnt need
> zero-extension. */
> return wi::ge_p (min, 0, rhs_signop);
> else
> /* If min >= 0 and max <= signed-max-of-type then range doesn't need
> sign-extension. */
> return wi::ge_p (min, 0, rhs_signop) && wi::le_p (max, limit,
> rhs_signop);
> }
>
> Thanks,
> Kugan
next prev parent reply other threads:[~2014-08-05 14:18 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-24 11:48 [PATCH 0/2] Zext/sext elimination using value range Kugan
2014-06-24 11:51 ` [PATCH 1/2] Enable setting sign and unsigned promoted mode (SPR_SIGNED_AND_UNSIGNED) Kugan
2014-06-24 12:18 ` Jakub Jelinek
2014-06-25 7:21 ` Kugan
2014-06-25 7:50 ` Jakub Jelinek
2014-06-26 1:06 ` Kugan
2014-06-26 2:48 ` Kugan
2014-06-26 5:50 ` Jakub Jelinek
2014-06-26 9:41 ` Kugan
2014-06-26 10:12 ` Jakub Jelinek
2014-06-26 10:42 ` Jakub Jelinek
2014-07-01 8:21 ` Kugan
2014-07-07 6:52 ` Kugan
2014-07-07 8:06 ` Jakub Jelinek
2014-06-26 10:25 ` Andreas Schwab
2014-07-01 8:28 ` Kugan
2014-06-24 11:53 ` [PATCH 2/2] Enable elimination of zext/sext Kugan
2014-06-24 12:21 ` Jakub Jelinek
2014-06-25 8:15 ` Kugan
2014-06-25 8:36 ` Jakub Jelinek
2014-07-07 6:55 ` Kugan
2014-07-10 12:15 ` Richard Biener
2014-07-11 11:52 ` Kugan
2014-07-11 12:47 ` Richard Biener
2014-07-14 2:58 ` Kugan
2014-07-14 20:11 ` Bernhard Reutner-Fischer
2014-07-23 14:22 ` Richard Biener
2014-08-01 4:51 ` Kugan
2014-08-01 11:16 ` Richard Biener
2014-08-01 16:04 ` Kugan
2014-08-03 23:56 ` Kugan
2014-08-05 14:18 ` Richard Biener [this message]
2014-08-05 14:21 ` Jakub Jelinek
2014-08-06 12:09 ` Richard Biener
2014-08-06 13:22 ` Kugan
2014-08-06 13:29 ` Richard Biener
2014-08-07 5:25 ` Kugan
2014-08-07 8:09 ` Richard Biener
2014-08-27 10:01 Uros Bizjak
2014-08-27 10:07 ` Richard Biener
2014-08-27 10:32 ` Uros Bizjak
2014-08-27 10:32 ` Richard Biener
2014-09-01 8:48 ` Jakub Jelinek
2014-09-01 8:54 ` Uros Bizjak
2014-08-28 7:50 ` Kugan
2014-08-28 8:57 ` Richard Biener
2014-09-04 3:41 ` Kugan
2014-09-04 13:00 ` Richard Biener
2014-09-05 1:33 ` Kugan
2014-09-05 9:51 ` Richard Biener
2014-09-07 9:51 ` Kugan
2014-09-08 9:48 ` Richard Biener
2014-09-09 10:06 ` Kugan
2014-09-09 10:28 ` Richard Biener
2014-08-27 13:02 ` Kugan
2014-08-28 3:46 ` Kugan
2014-08-28 6:44 ` Marc Glisse
2014-08-28 7:29 ` Kugan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAFiYyc1Gh6teQWgc44j+U1w8S6oyXHigPj8N0-MqTOVg1Xbn5Q@mail.gmail.com \
--to=richard.guenther@gmail.com \
--cc=gcc-patches@gcc.gnu.org \
--cc=jakub@redhat.com \
--cc=kugan.vivekanandarajah@linaro.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).