[Bug tree-optimization/38513] New: Only postreload will remove a no-op store

[Bug tree-optimization/38513] New: Only postreload will remove a no-op store

[pinskia at gcc dot gnu dot org]

Take:
struct f{
float a;
float b;
float c;
float d;
};

struct f a;

void h(float, float, float, float);

void g(void)
{
  float a1 = a.a, b = a.b, c = a.c, d = a.d;
  a.a = a1;
  a.b = b;
  a.c = c;
  a.d = d;
  h(a1, b, c, d);
}
--- CUT ---
Currently only postreload will remove the store back to a.a, a.b, a.c, and a.d.
 Note this code orginally came from inlined code and was just reduced to this.
And if this was done before postreload, we don't need a fmr which was produced
by the register allocator.


-- 
           Summary: Only postreload will remove a no-op store
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: pinskia at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38513

[Bug tree-optimization/38513] Only postreload will remove a no-op store

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2008-12-13 02:35 -------
Also note if we do -Dfloat=int on a target like PPC, the stores are not removed
because postreloadcse does not understand mode changes that well.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38513

[Bug tree-optimization/38513] Only postreload will remove a no-op store

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2008-12-13 02:37 -------
(In reply to comment #1)
> Also note if we do -Dfloat=int on a target like PPC, the stores are not removed
> because postreloadcse does not understand mode changes that well.

I should say PPC64 or -Dfloat=short for PPC.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38513

[Bug tree-optimization/38513] Only postreload will remove a no-op store

[rguenth at gcc dot gnu dot org]

------- Comment #3 from rguenth at gcc dot gnu dot org  2008-12-29 18:21 -------
I have a FRE patch.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |rguenth at gcc dot gnu dot
                   |dot org                     |org
             Status|UNCONFIRMED                 |ASSIGNED
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2008-12-29 18:21:58
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38513

[Bug tree-optimization/38513] Only postreload will remove a no-op store

[rguenth at gcc dot gnu dot org]

------- Comment #4 from rguenth at gcc dot gnu dot org  2008-12-29 19:23 -------
Created an attachment (id=17002)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=17002&action=view)
patch

The idea is simple - delete redundant stores whose RHS have the same
value-number
as the LHS.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38513

[Bug tree-optimization/38513] Only postreload will remove a no-op store

[pinskia at gcc dot gnu dot org]

------- Comment #5 from pinskia at gcc dot gnu dot org  2008-12-29 19:36 -------
*** Bug 21000 has been marked as a duplicate of this bug. ***


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38513

[Bug tree-optimization/38513] Only postreload will remove a no-op store

[pinskia at gcc dot gnu dot org]

------- Comment #6 from pinskia at gcc dot gnu dot org  2008-12-29 19:38 -------
(In reply to comment #4)
> The idea is simple - delete redundant stores whose RHS have the same
> value-number as the LHS.

Which is basically what postreload CSE does really:
      if (!count && reload_cse_noop_set_p (body))
        {
          rtx value = SET_DEST (body);
          if (REG_P (value)
              && ! REG_FUNCTION_VALUE_P (value))
            value = 0;
          delete_insn_and_edges (insn);
          return;
        }

:)


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38513

[Bug tree-optimization/38513] Only postreload will remove a no-op store

[pinskia at gcc dot gnu dot org]

------- Comment #7 from pinskia at gcc dot gnu dot org  2008-12-29 19:39 -------
One more testcase, we miss a sibcalling optimization due to this (this is
originally from PR 2100):
int i;
int g(void) __attribute__((pure));
int f()
{
  int t = i;
  int t1 = g();
  i = t;
  return t1;
}


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38513

[Bug tree-optimization/38513] Only postreload will remove a no-op store

[rguenth at gcc dot gnu dot org]

------- Comment #8 from rguenth at gcc dot gnu dot org  2009-03-28 10:11 -------
Subject: Bug 38513

Author: rguenth
Date: Sat Mar 28 10:11:14 2009
New Revision: 145172

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=145172
Log:
2009-03-28  Richard Guenther  <rguenther@suse.de>

        PR tree-optimization/38513
        * tree-ssa-pre.c (eliminate): Remove redundant stores.
        * tree-ssa-sccvn.c (copy_reference_ops_from_ref): Handle
        EXC_PTR_EXPR and FILTER_EXPR.
        (get_ref_from_reference_ops): Likewise.

        * gcc.dg/tree-ssa/ssa-fre-21.c: New testcase.
        * gcc.dg/tree-ssa/ssa-dse-11.c: Adjust.
        * gcc.dg/vect/vect-reduc-dot-u8a.c: Likewise.
        * gcc.dg/vect/vect-reduc-dot-u8b.c: Likewise.
        * gcc.dg/vect/slp-widen-mult-u8.c: Likewise.
        * gcc.dg/vect/vect-multitypes-16.c: Likewise.
        * gcc.dg/vect/vect-35.c: Likewise.
        * gcc.dg/vect/wrapv-vect-reduc-dot-s8b.c: Likewise.
        * gcc.dg/vect/vect-multitypes-17.c: Likewise.
        * gcc.dg/vect/slp-widen-mult-s16.c: Likewise.

Added:
    trunk/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-21.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-11.c
    trunk/gcc/testsuite/gcc.dg/vect/slp-widen-mult-s16.c
    trunk/gcc/testsuite/gcc.dg/vect/slp-widen-mult-u8.c
    trunk/gcc/testsuite/gcc.dg/vect/vect-35.c
    trunk/gcc/testsuite/gcc.dg/vect/vect-multitypes-16.c
    trunk/gcc/testsuite/gcc.dg/vect/vect-multitypes-17.c
    trunk/gcc/testsuite/gcc.dg/vect/vect-reduc-dot-u8a.c
    trunk/gcc/testsuite/gcc.dg/vect/vect-reduc-dot-u8b.c
    trunk/gcc/testsuite/gcc.dg/vect/wrapv-vect-reduc-dot-s8b.c
    trunk/gcc/tree-ssa-pre.c
    trunk/gcc/tree-ssa-sccvn.c


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38513

[Bug tree-optimization/38513] Only postreload will remove a no-op store

[rguenth at gcc dot gnu dot org]

------- Comment #9 from rguenth at gcc dot gnu dot org  2009-03-28 10:12 -------
Fixed.


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rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.5.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38513