[Bug tree-optimization/81503] [8 Regression] Wrong code at -O2

[aldyh at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81503

--- Comment #22 from Aldy Hernandez  ---
Author: aldyh
Date: Wed Sep 13 17:36:05 2017
New Revision: 252605

URL: https://gcc.gnu.org/viewcvs?rev=252605=gcc=rev
Log:
[gcc]

2017-08-29  Bill Schmidt  
Jakub Jelinek  
Richard Biener  

PR tree-optimization/81503
* gimple-ssa-strength-reduction.c (replace_mult_candidate): Ensure
folded constant fits in the target type; reorder tests for clarity.

[gcc/testsuite]

2017-08-29  Bill Schmidt  

PR tree-optimization/81503
* gcc.c-torture/execute/pr81503.c: New file.

Added:
branches/range-gen2/gcc/testsuite/gcc.c-torture/execute/pr81503.c
Modified:
branches/range-gen2/gcc/ChangeLog
branches/range-gen2/gcc/gimple-ssa-strength-reduction.c
branches/range-gen2/gcc/testsuite/ChangeLog

[Bug tree-optimization/81503] [8 Regression] Wrong code at -O2

[wschmidt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81503

Bill Schmidt  changed:

   What|Removed |Added

 Status|NEW |RESOLVED
 Resolution|--- |FIXED

--- Comment #21 from Bill Schmidt  ---
Fixed everywhere now.

[Bug tree-optimization/81503] [8 Regression] Wrong code at -O2

[wschmidt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81503

--- Comment #20 from Bill Schmidt  ---
Author: wschmidt
Date: Tue Sep  5 21:52:01 2017
New Revision: 251745

URL: https://gcc.gnu.org/viewcvs?rev=251745=gcc=rev
Log:
[gcc]

2017-09-05  Bill Schmidt  

Backport from mainline
2017-08-29  Bill Schmidt  
Jakub Jelinek  
Richard Biener  

PR tree-optimization/81503
* gimple-ssa-strength-reduction.c (replace_mult_candidate): Ensure
folded constant fits in the target type; reorder tests for clarity.

[gcc/testsuite]

2017-09-05  Bill Schmidt  

Backport from mainline
2017-08-29  Bill Schmidt  
Jakub Jelinek  
Richard Biener  

PR tree-optimization/81503
* gcc.c-torture/execute/pr81503.c: New file.


Added:
branches/gcc-5-branch/gcc/testsuite/gcc.c-torture/execute/pr81503.c
Modified:
branches/gcc-5-branch/gcc/ChangeLog
branches/gcc-5-branch/gcc/gimple-ssa-strength-reduction.c
branches/gcc-5-branch/gcc/testsuite/ChangeLog

[Bug tree-optimization/81503] [8 Regression] Wrong code at -O2

[wschmidt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81503

--- Comment #19 from Bill Schmidt  ---
Author: wschmidt
Date: Tue Sep  5 21:50:38 2017
New Revision: 251744

URL: https://gcc.gnu.org/viewcvs?rev=251744=gcc=rev
Log:
[gcc]

2017-09-05  Bill Schmidt  

Backport from mainline
2017-08-29  Bill Schmidt  
Jakub Jelinek  
Richard Biener  

PR tree-optimization/81503
* gimple-ssa-strength-reduction.c (replace_mult_candidate): Ensure
folded constant fits in the target type; reorder tests for clarity.

[gcc/testsuite]

2017-09-05  Bill Schmidt  

Backport from mainline
2017-08-29  Bill Schmidt  
Jakub Jelinek  
Richard Biener  

PR tree-optimization/81503
* gcc.c-torture/execute/pr81503.c: New file.


Added:
branches/gcc-6-branch/gcc/testsuite/gcc.c-torture/execute/pr81503.c
Modified:
branches/gcc-6-branch/gcc/ChangeLog
branches/gcc-6-branch/gcc/gimple-ssa-strength-reduction.c
branches/gcc-6-branch/gcc/testsuite/ChangeLog

[Bug tree-optimization/81503] [8 Regression] Wrong code at -O2

[wschmidt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81503

--- Comment #18 from Bill Schmidt  ---
Author: wschmidt
Date: Tue Sep  5 21:49:01 2017
New Revision: 251743

URL: https://gcc.gnu.org/viewcvs?rev=251743=gcc=rev
Log:
[gcc]

2017-09-05  Bill Schmidt  

Backport from mainline
2017-08-29  Bill Schmidt  
Jakub Jelinek  
Richard Biener  

PR tree-optimization/81503
* gimple-ssa-strength-reduction.c (replace_mult_candidate): Ensure
folded constant fits in the target type; reorder tests for clarity.

[gcc/testsuite]

2017-09-05  Bill Schmidt  

Backport from mainline
2017-08-29  Bill Schmidt  
Jakub Jelinek  
Richard Biener  

PR tree-optimization/81503
* gcc.c-torture/execute/pr81503.c: New file.


Added:
branches/gcc-7-branch/gcc/testsuite/gcc.c-torture/execute/pr81503.c
Modified:
branches/gcc-7-branch/gcc/ChangeLog
branches/gcc-7-branch/gcc/gimple-ssa-strength-reduction.c
branches/gcc-7-branch/gcc/testsuite/ChangeLog

[Bug tree-optimization/81503] [8 Regression] Wrong code at -O2

[wschmidt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81503

--- Comment #17 from Bill Schmidt  ---
Fixed in trunk so far.  Although this test case succeeds on GCC 7, the bug is
latent there, so I'll keep this open and backport the fix to other releases in
a week or so.

[Bug tree-optimization/81503] [8 Regression] Wrong code at -O2

[wschmidt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81503

--- Comment #16 from Bill Schmidt  ---
Author: wschmidt
Date: Tue Aug 29 14:41:53 2017
New Revision: 251414

URL: https://gcc.gnu.org/viewcvs?rev=251414=gcc=rev
Log:
[gcc]

2017-08-29  Bill Schmidt  
Jakub Jelinek  
Richard Biener  

PR tree-optimization/81503
* gimple-ssa-strength-reduction.c (replace_mult_candidate): Ensure
folded constant fits in the target type; reorder tests for clarity.

[gcc/testsuite]

2017-08-29  Bill Schmidt  

PR tree-optimization/81503
* gcc.c-torture/execute/pr81503.c: New file.


Added:
trunk/gcc/testsuite/gcc.c-torture/execute/pr81503.c
Modified:
trunk/gcc/ChangeLog
trunk/gcc/gimple-ssa-strength-reduction.c
trunk/gcc/testsuite/ChangeLog

[Bug tree-optimization/81503] [8 Regression] Wrong code at -O2

[wschmidt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81503

--- Comment #15 from Bill Schmidt  ---
Proposed patch awaiting approval: 
https://gcc.gnu.org/ml/gcc-patches/2017-08/msg00347.html

[Bug tree-optimization/81503] [8 Regression] Wrong code at -O2

[wschmidt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81503

--- Comment #14 from Bill Schmidt  ---
Created attachment 41899
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41899=edit
Patch under test

This is the patch I'm currently looking at.  I am unhappy at having to use a
tree to get maxval, but I cannot find a way to convert a wide_int into a
widest_int so that I can add them together (see the desired code that is
commented out).  Do you have a suggestion how I can do this within the wide_int
framework?

[Bug tree-optimization/81503] [8 Regression] Wrong code at -O2

[wschmidt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81503

--- Comment #13 from Bill Schmidt  ---
(In reply to Jakub Jelinek from comment #12)
> I had in mind something like
> wi::eq_p (wi::ext (w, TYPE_PRECISION (type), TYPE_SIGN (type)), w)
> or so.

Ah, good, thank you.

[Bug tree-optimization/81503] [8 Regression] Wrong code at -O2

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81503

--- Comment #12 from Jakub Jelinek  ---
I had in mind something like
wi::eq_p (wi::ext (w, TYPE_PRECISION (type), TYPE_SIGN (type)), w)
or so.

[Bug tree-optimization/81503] [8 Regression] Wrong code at -O2

[wschmidt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81503

--- Comment #11 from Bill Schmidt  ---
(In reply to Jakub Jelinek from comment #10)
> The TREE_INT_CST_LOW part looks suspicious.  Also, wide-int.h should provide
> enough infrastructure so that you should be able to do everything on
> wide-int, not have to create trees.

I just saw this comment now.  I think that the TREE_INT_CST_LOW is ok given
that we've already constrained bump to fit in a HOST_WIDE_INT, right?  But
anyway, your second point is well taken -- it looks like I can make use of
wi::to_uhwi and wi::to_shwi with a specified precision from the target type, so
use of trees should indeed be unnecessary.

I have a working patch that uses the trees, but I will rework that in favor of
a pure wide-int solution.  Thanks for the suggestion!

Bill

[Bug tree-optimization/81503] [8 Regression] Wrong code at -O2

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81503

Jakub Jelinek  changed:

   What|Removed |Added

 CC||jakub at gcc dot gnu.org

--- Comment #10 from Jakub Jelinek  ---
The TREE_INT_CST_LOW part looks suspicious.  Also, wide-int.h should provide
enough infrastructure so that you should be able to do everything on wide-int,
not have to create trees.

[Bug tree-optimization/81503] [8 Regression] Wrong code at -O2

[wschmidt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81503

--- Comment #9 from Bill Schmidt  ---
This is overkill, it has some test case fallout.  Will have to look a bit
deeper.

[Bug tree-optimization/81503] [8 Regression] Wrong code at -O2

[wschmidt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81503

--- Comment #8 from Bill Schmidt  ---
Patch under test that fixes this case:

Index: gcc/gimple-ssa-strength-reduction.c  
===
--- gcc/gimple-ssa-strength-reduction.c (revision 250791)   
+++ gcc/gimple-ssa-strength-reduction.c (working copy)  
@@ -2082,6 +2082,11 @@ replace_mult_candidate (slsr_cand_t c, tree basis_
  types but allows for safe negation without twisted logic.  */ 
   if (wi::fits_shwi_p (bump)   
   && bump.to_shwi () != HOST_WIDE_INT_MIN  
+  /* It is more likely that the bump doesn't fit in the target 
+type, so check whether constraining it to that type changes
+the value.  */ 
+  && wi::eq_p (TREE_INT_CST_LOW (wide_int_to_tree (target_type, bump)),
+  bump)
   /* It is not useful to replace casts, copies, negates, or adds of
 an SSA name and a constant.  */
   && cand_code != SSA_NAME

[Bug tree-optimization/81503] [8 Regression] Wrong code at -O2

[wschmidt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81503

--- Comment #7 from Bill Schmidt  ---
Try -fno-slsr.

[Bug tree-optimization/81503] [8 Regression] Wrong code at -O2

[babokin at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81503

--- Comment #6 from Dmitry Babokin  ---
How can I switch off optimization phases to workaround the bug?

I have another instances of wrong code bugs, so I'd like to make sure that I
don't create duplicate reports for the same problem.

[Bug tree-optimization/81503] [8 Regression] Wrong code at -O2

[wschmidt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81503

Bill Schmidt  changed:

   What|Removed |Added

   Assignee|unassigned at gcc dot gnu.org  |wschmidt at gcc dot 
gnu.org

--- Comment #5 from Bill Schmidt  ---
Mine, but my queue is getting pretty deep, so it will be a bit before I look at
it.

[Bug tree-optimization/81503] [8 Regression] Wrong code at -O2

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81503

--- Comment #4 from Marc Glisse  ---
  if (a + b * -2)
c = (b-1073741824)*-2;

might let you find an earlier culprit.

[Bug tree-optimization/81503] [8 Regression] Wrong code at -O2

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81503

Martin Liška  changed:

   What|Removed |Added

 CC||marxin at gcc dot gnu.org

--- Comment #3 from Martin Liška  ---
Started with r249447:

gcc/
* match.pd (nop_convert): New predicate.
((A +- CST1) +- CST2): Allow some NOP conversions.

gcc/testsuite/
* gcc.dg/tree-ssa/addadd.c: Un-XFAIL.
* gcc.dg/tree-ssa/addadd-2.c: New file.

[Bug tree-optimization/81503] [8 Regression] Wrong code at -O2

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81503

Richard Biener  changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
   Last reconfirmed||2017-07-21
 CC||wschmidt at gcc dot gnu.org
  Known to work||7.1.1
   Target Milestone|--- |8.0
Summary|Wrong code at -O2   |[8 Regression] Wrong code
   ||at -O2
 Ever confirmed|0   |1

--- Comment #2 from Richard Biener  ---
Seems to work with GCC 7.