[Bug middle-end/35308] New: Straight line strength reduction

[Bug middle-end/35308] New: Straight line strength reduction

[xinliangli at gmail dot com]

Seems to be a missing functionality

int a[100];
int g;
void foo(int i)
{

     a[i] = i*g;
     i++;
     a[i] = i*g;
     i++;
     a[i] = i*g;
}

Both array address computation and RHS mpy operations can be strength reduced.


-- 
           Summary: Straight line strength reduction
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: xinliangli at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35308

[Bug middle-end/35308] Straight line strength reduction

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2008-02-23 05:27 -------
Sometimes doing the strength reduction actually increases the code size.  Think
on targets which have auto increments.

*** This bug has been marked as a duplicate of 22586 ***


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |DUPLICATE


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35308

[Bug middle-end/35308] Straight line strength reduction

[xinliangli at gmail dot com]

------- Comment #2 from xinliangli at gmail dot com  2008-02-23 06:55 -------
(In reply to comment #1)
> Sometimes doing the strength reduction actually increases the code size.  Think
> on targets which have auto increments.
> 
> *** This bug has been marked as a duplicate of 22586 ***
> 

Itanium supports address post increment.  The postInc synthesis phase should
not be affected by the strengh reduced address computation code.

When this is fixed by the PRE framework, make sure the conditional increment
case is also covered:

a[i] = i*g;
if (...)
{
   i++;
}
a[i] += ...
... = i*g;


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35308

[Bug middle-end/35308] Straight line strength reduction

[wschmidt at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35308

William J. Schmidt <wschmidt at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
           Keywords|                            |missed-optimization
   Last reconfirmed|                            |2012-06-28
                 CC|                            |wschmidt at gcc dot gnu.org
         AssignedTo|unassigned at gcc dot       |wschmidt at gcc dot gnu.org
                   |gnu.org                     |
         Resolution|DUPLICATE                   |
     Ever Confirmed|0                           |1
   Target Milestone|---                         |4.8.0

--- Comment #3 from William J. Schmidt <wschmidt at gcc dot gnu.org> 2012-06-28 01:36:25 UTC ---
Reopening this one since the cases in this bug report (unknown stride,
conditional candidate) are not yet handled by the new strength reduction pass. 
I will re-close once those additional features are in place.

[Bug middle-end/35308] Straight line strength reduction

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35308

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.8.0                       |4.8.1

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-03-22 14:46:02 UTC ---
GCC 4.8.0 is being released, adjusting target milestone.

[Bug middle-end/35308] Straight line strength reduction

[wschmidt at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35308

William J. Schmidt <wschmidt at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.8.1                       |4.9.0

--- Comment #5 from William J. Schmidt <wschmidt at gcc dot gnu.org> 2013-03-25 13:17:39 UTC ---
The unknown stride features made it into 4.8.0, but conditional candidates are
still pending, and too complex for 4.8.1, I think.  Changing target to 4.9 for
the remaining work.  I do plan to get that wrapped up fairly soon.

[Bug middle-end/35308] Straight line strength reduction

[wschmidt at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35308

Bill Schmidt <wschmidt at gcc dot gnu.org> changed:

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

--- Comment #6 from Bill Schmidt <wschmidt at gcc dot gnu.org> ---
Conditional candidate processing was completed a couple of months ago.  While
there are improvements I plan to look at someday, the basic work is done, so
closing the issue.