[Bug tree-optimization/70171] Poor code generated when return struct using ternary operator

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70171

Richard Biener  changed:

   What|Removed |Added

 Status|ASSIGNED|RESOLVED
  Known to work||7.0
 Resolution|--- |FIXED

--- Comment #10 from Richard Biener  ---
Fixed for GCC 7.

[Bug tree-optimization/70171] Poor code generated when return struct using ternary operator

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70171

--- Comment #9 from Richard Biener  ---
Author: rguenth
Date: Tue Apr 19 14:03:59 2016
New Revision: 235208

URL: https://gcc.gnu.org/viewcvs?rev=235208&root=gcc&view=rev
Log:
2016-04-19  Richard Biener  

PR tree-optimization/70171
* tree-ssa-phiprop.c: Include stor-layout.h.
(phiprop_insert_phi): Handle the aggregate copy case.
(propagate_with_phi): Likewise.

* g++.dg/tree-ssa/pr70171.C: New testcase.

Added:
trunk/gcc/testsuite/g++.dg/tree-ssa/pr70171.C
Modified:
trunk/gcc/ChangeLog
trunk/gcc/testsuite/ChangeLog
trunk/gcc/tree-ssa-phiprop.c

[Bug tree-optimization/70171] Poor code generated when return struct using ternary operator

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70171

--- Comment #8 from Richard Biener  ---
(In reply to Oleg Endo from comment #7)
> Is this a dup of PR 56365?  Sounds like so ...

No, not really.

[Bug tree-optimization/70171] Poor code generated when return struct using ternary operator

[olegendo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70171

Oleg Endo  changed:

   What|Removed |Added

 CC||olegendo at gcc dot gnu.org

--- Comment #7 from Oleg Endo  ---
Is this a dup of PR 56365?  Sounds like so ...

[Bug tree-optimization/70171] Poor code generated when return struct using ternary operator

[rguenther at suse dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70171

--- Comment #6 from rguenther at suse dot de  ---
On Fri, 11 Mar 2016, ubizjak at gmail dot com wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70171
> 
> --- Comment #5 from Uroš Bizjak  ---
> (In reply to Richard Biener from comment #4)
> > Created attachment 37935 [details]
> > patch
> > 
> > Patch I am testing.
> 
> + /* { dg-final { scan-assembler-not "\[er\]sp" { target x86_64-*-* } } } */
> 
> You should always use "target i?86-*-* x86_64-*-*" and optionally limit to
> 64bit targets with "&& { ! ia32 }". Please see many examples in gcc.dg.

Will do.

[Bug tree-optimization/70171] Poor code generated when return struct using ternary operator

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70171

--- Comment #5 from Uroš Bizjak  ---
(In reply to Richard Biener from comment #4)
> Created attachment 37935 [details]
> patch
> 
> Patch I am testing.

+ /* { dg-final { scan-assembler-not "\[er\]sp" { target x86_64-*-* } } } */

You should always use "target i?86-*-* x86_64-*-*" and optionally limit to
64bit targets with "&& { ! ia32 }". Please see many examples in gcc.dg.

[Bug tree-optimization/70171] Poor code generated when return struct using ternary operator

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70171

--- Comment #4 from Richard Biener  ---
Created attachment 37935
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=37935&action=edit
patch

Patch I am testing.

[Bug tree-optimization/70171] Poor code generated when return struct using ternary operator

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70171

Richard Biener  changed:

   What|Removed |Added

 CC||jason at gcc dot gnu.org

--- Comment #3 from Richard Biener  ---
Btw, the C frontend produces optimized code here - it simply uses

  return select != 0 ? a : b;

in its GENERIC.  Maybe the C++ FE can avoid building a TARGET_EXPR like that
or use 

return  = TARGET_EXPR 

that is, without going through the address-taking and dereferencing game?

[Bug tree-optimization/70171] Poor code generated when return struct using ternary operator

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70171

Richard Biener  changed:

   What|Removed |Added

   Keywords||missed-optimization
 Status|UNCONFIRMED |ASSIGNED
   Last reconfirmed||2016-03-11
  Component|c++ |tree-optimization
   Assignee|unassigned at gcc dot gnu.org  |rguenth at gcc dot 
gnu.org
 Ever confirmed|0   |1

--- Comment #2 from Richard Biener  ---
This is the C++ frontends work:

;; Function S struct_ternary(S, S, bool) (null)
;; enabled by -tree-original


< = TARGET_EXPR >>;

and while we have a pass that cleans this up for scalars it refuses to
operate on aggregates (because it tries to use a PHI in the transform).
Thus phiprop could handle this case emitting non-SSA code here and
do this for aggregates with non-BLKmode.  Basically transform

  :
  if (select_2(D) != 0)
goto ;
  else
goto ;

  :

  :
  # iftmp.1_1 = PHI <&a(2), &b(3)>
  D.2322 = MEM[(const struct S &)iftmp.1_1];

into

  :
  if (select_2(D) != 0)
goto ;
  else
goto ;

  :
D.2322 = b;
goto ;

  :
D.2322 = a;

  :


Let me try to tackle this for GCC 7.