[Bug middle-end/33315] If condition not getting eliminated

[Bug middle-end/33315] If condition not getting eliminated

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33315

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> 2012-02-04 02:33:16 UTC ---
tail merge should be able to do this.  It currently does not though for the
provided testcase in comment #1 but that is PR 52009.
Also note cselim should be able to do it too.

[Bug tree-optimization/33315] stores not commoned by sinking

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=33315

--- Comment #12 from Richard Biener <rguenth at gcc dot gnu.org> ---
Created attachment 48279
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48279&action=edit
patch

Patch forward ported to current trunk.

[Bug tree-optimization/33315] stores not commoned by sinking

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=33315

--- Comment #13 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #12)
> Created attachment 48279 [details]
> patch
> 
> Patch forward ported to current trunk.

Surprisingly small fallout:

FAIL: gcc.dg/tree-ssa/split-path-7.c scan-tree-dump-times split-paths
"Duplicating join block" 0

I've thought the approach is too simplistic but I'll do some statistics
over bootstrap in stage1 and push it if it looks useful - we certainly
have more "hackish" optimization pieces.

[Bug tree-optimization/33315] stores not commoned by sinking

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=33315

--- Comment #14 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #13)
> (In reply to Richard Biener from comment #12)
> > Created attachment 48279 [details]
> > patch
> > 
> > Patch forward ported to current trunk.
> 
> Surprisingly small fallout:
> 
> FAIL: gcc.dg/tree-ssa/split-path-7.c scan-tree-dump-times split-paths
> "Duplicating join block" 0
> 
> I've thought the approach is too simplistic but I'll do some statistics
> over bootstrap in stage1 and push it if it looks useful - we certainly
> have more "hackish" optimization pieces.

stage3 gcc/ files show (first column is the number of edges we sink from,
second column the number of stores we sink):

2: 3195
3: 193
4: 130
5: 55
6: 28
7: 4
8: 9
9: 3
10: 3
12: 1
13: 6
16: 2
18: 1
22: 2

so it seems worth it.

[Bug tree-optimization/33315] stores not commoned by sinking

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=33315

--- Comment #15 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:84935c9822183ce403bb361c5f405711b9a808c6

commit r11-408-g84935c9822183ce403bb361c5f405711b9a808c6
Author: Richard Biener <rguenther@suse.de>
Date:   Wed Apr 15 12:09:01 2020 +0200

    tree-optimization/33315 - common stores during sinking

    This implements commoning of stores to a common successor in
    a simple ad-hoc way.  I've decided to put it into the code sinking
    pass since, well, it sinks stores.  It's still separate since
    it does not really sink code into less executed places.

    It's ad-hoc since it does not perform any dataflow or alias analysis
    but simply only considers trailing stores in a block, iteratively
    though.  If the stores are from different values a PHI node is
    inserted to merge them.  gcc.dg/tree-ssa/split-path-7.c shows
    that path splitting will eventually undo this very transform,
    I've decided to not bother with it and simply disable sinking for
    the particular testcase.

    Doing this transform is good for code size when the stores are
    from constants, once we have to insert PHIs the situation becomes
    less clear but it's a transform we do elsewhere as well
    (cselim for one), and reversing the transform should be easy.

    2020-05-15  Richard Biener  <rguenther@suse.de>

            PR tree-optimization/33315
            * tree-ssa-sink.c: Include tree-eh.h.
            (sink_stats): Add commoned member.
            (sink_common_stores_to_bb): New function implementing store
            commoning by sinking to the successor.
            (sink_code_in_bb): Call it, pass down TODO_cleanup_cfg returned.
            (pass_sink_code::execute): Likewise.  Record commoned stores
            in statistics.

            * gcc.dg/tree-ssa/ssa-sink-13.c: New testcase.
            * gcc.dg/tree-ssa/ssa-sink-14.c: Likewise.
            * gcc.dg/tree-ssa/split-path-7.c: Disable sinking.

[Bug tree-optimization/33315] stores not commoned by sinking

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=33315

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #16 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed on trunk.  Individual missed cases should be tracked by separate
bugreports.

[Bug middle-end/33315] New: If condition not getting eliminated

[pranav dot bhandarkar at gmail dot com]

if ( x == 8 ) statement1
if ( x != 8 ) statement1
if ( x == 9 ) statement2
if ( x != 9 ) statement2
should be replaced by

statement1
statement2

However this doesnt happen and compare and jumps do get generated.


-- 
           Summary: If condition not getting eliminated
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: pranav dot bhandarkar at gmail dot com
GCC target triplet: arm-none-eabi


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33315

[Bug middle-end/33315] If condition not getting eliminated

[pranav dot bhandarkar at gmail dot com]

------- Comment #1 from pranav dot bhandarkar at gmail dot com  2007-09-05 19:03 -------
Created an attachment (id=14158)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=14158&action=view)
Sample Testcase


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33315

[Bug middle-end/33315] If condition not getting eliminated

[steven at gcc dot gnu dot org]

------- Comment #3 from steven at gcc dot gnu dot org  2007-11-10 00:27 -------
As a missed optimization, this bug adds new information.  But as a regression,
this is a dup of bug 30905.


-- 

steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.3 Regression] If         |If condition not getting
                   |condition not getting       |eliminated
                   |eliminated                  |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33315

[Bug middle-end/33315] If condition not getting eliminated

[j at uriah dot heep dot sax dot de]

------- Comment #4 from j at uriah dot heep dot sax dot de  2007-11-23 10:57 -------
Is the missed optimization in the following code the same?

volatile unsigned char *reg_a = (unsigned char *)42;
volatile unsigned char *reg_b = (unsigned char *)34;

extern void a(void);
extern void b(void);
extern void c(void);

void
decide(void)
{
        signed char diff;

        diff = *reg_a - *reg_b;

        if (diff < 0)
                a();
        else if (diff == 0)
                b();
        else if (diff > 0)
                c();
}

The third "if" statement is partially executed: it apparently remembered
that diff could not be less than 0, but it still tests against 0 even
though that test has just been done before.  Verified on both, the AVR
and i386 target.

Interestingly, by just reordering the code, the third condition will
be eliminated by GCC 4.x (but not by GCC 3.x):

volatile unsigned char *reg_a = (unsigned char *)42;
volatile unsigned char *reg_b = (unsigned char *)34;

extern void a(void);
extern void b(void);
extern void c(void);

void
decide(void)
{
        signed char diff;

        diff = *reg_a - *reg_b;

        if (diff < 0)
                a();
        else if (diff > 0)
                c();
        else if (diff == 0)
                b();
}

If someone thinks that's an entirely different thing than the subject of this
bug, please tell me so, and I'll submit a separate one.


-- 

j at uriah dot heep dot sax dot de changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |j at uriah dot heep dot sax
                   |                            |dot de


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33315

[Bug middle-end/33315] If condition not getting eliminated

[rguenth at gcc dot gnu dot org]

-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.3.0                       |---


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33315

[Bug middle-end/33315] If condition not getting eliminated

[dave at icerasemi dot com]

------- Comment #5 from dave at icerasemi dot com  2008-10-21 08:28 -------
Subject: RE:  If condition not getting eliminated


Hi Ramana,

Please could you add sdkteam-gnu@icerasemi.com - then we all get to see
it ;-)

Cheers,


-----Original Message-----
From: ramana at icerasemi dot com [mailto:gcc-bugzilla@gcc.gnu.org] 
Sent: 21 October 2008 08:04
To: Dave Edwards
Subject: [Bug middle-end/33315] If condition not getting eliminated



-- 

ramana at icerasemi dot com changed:

           What    |Removed                     |Added
------------------------------------------------------------------------
----
                 CC|                            |ramana at icerasemi dot
com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33315

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-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33315

[Bug middle-end/33315] If condition not getting eliminated

[pinskia at gcc dot gnu dot org]

-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33315