[Bug tree-optimization/23109] [4.1 Regression] compiler generates wrong code leading to spurious division by zero with -funsafe-math-optimizations (instead of -ftrapping-math)

[Bug tree-optimization/23109] [4.1 Regression] compiler generates wrong code leading to spurious division by zero with -funsafe-math-optimizations (instead of -ftrapping-math)

[bonzini at gcc dot gnu dot org]

------- Comment #6 from bonzini at gcc dot gnu dot org  2005-10-14 12:00 -------
I'm not sure this is really fixed.

With this test case,

float a = g();
printf ("%g\n", a);
printf ("%g\n", 2 / a);
printf ("%g\n", 3 / a);

the division is inserted before the *first* printf, while I believe it should
be inserted before the second.

The patch in pr23948 tries to insert reciprocals before the use point, rather
than after the def point, which would fix this as well.

Should this bug be reopened?


-- 

bonzini at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  BugsThisDependsOn|                            |23948


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23109

[Bug tree-optimization/23109] [4.1 Regression] compiler generates wrong code leading to spurious division by zero with -funsafe-math-optimizations (instead of -ftrapping-math)

[rguenth at gcc dot gnu dot org]

------- Comment #7 from rguenth at gcc dot gnu dot org  2005-10-14 12:13 -------
Yes, I think so.  You don't even need printf, but any observable side-effect,
like a store to a global will do.


-- 

rguenth at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23109

[Bug tree-optimization/23109] [4.1 Regression] compiler generates wrong code leading to spurious division by zero with -funsafe-math-optimizations (instead of -ftrapping-math)

[rguenth at gcc dot gnu dot org]

-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                URL|                            |http://gcc.gnu.org/ml/gcc-
                   |                            |patches/2005-
                   |                            |10/msg00687.html
           Severity|minor                       |major
 GCC target triplet|i686-pc-linux-gnu           |
           Keywords|                            |patch


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23109

[Bug tree-optimization/23109] [4.1 Regression] compiler generates wrong code leading to spurious division by zero with -funsafe-math-optimizations (instead of -ftrapping-math)

[rguenth at gcc dot gnu dot org]

-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|rguenth at gcc dot gnu dot  |bonzini at gcc dot gnu dot
                   |org                         |org
             Status|REOPENED                    |ASSIGNED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23109

[Bug tree-optimization/23109] [4.1 Regression] compiler generates wrong code leading to spurious division by zero with -funsafe-math-optimizations (instead of -ftrapping-math)

[pinskia at gcc dot gnu dot org]

-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|major                       |critical


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23109

[Bug tree-optimization/23109] [4.1 Regression] compiler generates wrong code leading to spurious division by zero with -funsafe-math-optimizations (instead of -ftrapping-math)

[mmitchel at gcc dot gnu dot org]

------- Comment #8 from mmitchel at gcc dot gnu dot org  2005-10-31 04:20 -------
This is a serious wrong-code problem; it's a showstopper.


-- 

mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P2                          |P1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23109

[Bug tree-optimization/23109] [4.1 Regression] compiler generates wrong code leading to spurious division by zero with -funsafe-math-optimizations (instead of -ftrapping-math)

[bonzini at gcc dot gnu dot org]

------- Comment #9 from bonzini at gcc dot gnu dot org  2005-11-01 22:00 -------
It is a showstopper, but a patch has been ready for months...  I admit the
patch is non-trivial, but the testcases are comprehensive.

Maybe it's best to wait until the branch and backport it a week later.  But I
don't think so.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23109

[Bug tree-optimization/23109] [4.1 Regression] compiler generates wrong code leading to spurious division by zero with -funsafe-math-optimizations (instead of -ftrapping-math)

[rguenth at gcc dot gnu dot org]

------- Comment #10 from rguenth at gcc dot gnu dot org  2005-11-01 22:17 -------
Note that the patch is in the suse compiler since three weeks now without a
problem.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23109

[Bug tree-optimization/23109] [4.1 Regression] compiler generates wrong code leading to spurious division by zero with -funsafe-math-optimizations (instead of -ftrapping-math)

[bonzini at gcc dot gnu dot org]

------- Comment #11 from bonzini at gcc dot gnu dot org  2005-11-03 10:05 -------
Note that while PR23948 could be fixed by hacking the current recip pass so
that it inserts the division into another basic block, this is not true of this
bug. 


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23109

[Bug tree-optimization/23109] [4.1 Regression] compiler generates wrong code leading to spurious division by zero with -funsafe-math-optimizations (instead of -ftrapping-math)

[steven at gcc dot gnu dot org]

------- Comment #12 from steven at gcc dot gnu dot org  2005-11-16 14:12 -------
Is this bug going anywhere???


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23109

[Bug tree-optimization/23109] [4.1 Regression] compiler generates wrong code leading to spurious division by zero with -funsafe-math-optimizations (instead of -ftrapping-math)

[rguenth at gcc dot gnu dot org]

------- Comment #13 from rguenth at gcc dot gnu dot org  2005-11-16 14:16 -------
Nobody reviewed the patch AFAIK.  Still the patch hasn't caused any problems
sofar in the SUSE compiler.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mmitchel at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23109

[Bug tree-optimization/23109] [4.1 Regression] compiler generates wrong code leading to spurious division by zero with -funsafe-math-optimizations (instead of -ftrapping-math)

[bonzini at gcc dot gnu dot org]

------- Comment #14 from bonzini at gcc dot gnu dot org  2005-11-16 14:46 -------
I have little hope of seeing this reviewed before the branch.  But it should be
put in 4.2 very early so that we backport it well before 4.1.0 is released.

BTW I think that 23948 and 24123 are way more severe than 23109 even though
this one is a wrong code bug.  These three bugs are three almost-showstoppers,
and are actually different manifestations of the same basic flaw (recip should
insert temporaries near the uses, not near the defs).  PR23948 makes
-ffast-math unusable in C++, and PR24123 generates really abysmal code (20x
slower!).

Paolo


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23109

[Bug tree-optimization/23109] [4.1/4.2 Regression] compiler generates wrong code leading to spurious division by zero with -funsafe-math-optimizations (instead of -ftrapping-math)

[bonzini at gcc dot gnu dot org]

------- Comment #15 from bonzini at gnu dot org  2006-01-11 13:02 -------
Subject: Bug 23109

Author: bonzini
Date: Wed Jan 11 13:02:18 2006
New Revision: 109578

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=109578
Log:
gcc:
2006-01-11  Paolo Bonzini  <bonzini@gnu.org>

        PR tree-optimization/23109
        PR tree-optimization/23948
        PR tree-optimization/24123

        * Makefile.in (tree-ssa-math-opts.o): Adjust dependencies.
        * tree-cfg.c (single_noncomplex_succ): New.
        * tree-flow.h (single_noncomplex_succ): Declare it.
        * tree-ssa-math-opts.c (enum place_reciprocal): Remove.
        * tree-ssa-math-opts.c (enum place_reciprocal): Remove.
        (struct occurrence, occ_head, occ_pool, is_divide_by, compute_merit,
        insert_bb, register_division_in, insert_reciprocals,
        replace_reciprocal, free_bb): New.
        (execute_cse_reciprocals_1): Rewritten.
        (execute_cse_reciprocals): Adjust calls to execute_cse_reciprocals_1.
        Do not commit any edge insertion.  Always compute dominators and
        create the allocation pool.
        * target-def.h (TARGET_MIN_DIVISIONS_FOR_RECIP_MUL): New.
        * target.h (struct gcc_target): Add min_divistions_for_recip_mul.
        * targhooks.c (default_min_divistions_for_recip_mul): New.
        * targhooks.h (default_min_divistions_for_recip_mul): New prototype.
        * passes.c (init_optimization_passes): Run recip after tree loop
        optimizations.
        * doc/tm.texi (Misc): Document TARGET_MIN_DIVISIONS_FOR_RECIP_MUL.

gcc/testsuite:
2006-01-11  Paolo Bonzini  <bonzini@gnu.org>

        PR tree-optimization/23109
        PR tree-optimization/23948
        PR tree-optimization/24123

        * gcc.dg/tree-ssa/recip-3.c, gcc.dg/tree-ssa/recip-4.c,
        gcc.dg/tree-ssa/recip-5.c, gcc.dg/tree-ssa/recip-6.c,
        gcc.dg/tree-ssa/recip-7.c, gcc.dg/tree-ssa/pr23109.c,
        g++.dg/tree-ssa/pr23948.C: New testcases.
        * gcc.dg/tree-ssa/recip-2.c, gcc.dg/tree-ssa/pr23234.c: Provide
        three divisions in order to do the optimization.


Added:
    trunk/gcc/testsuite/g++.dg/tree-ssa/pr23948.C
    trunk/gcc/testsuite/gcc.dg/tree-ssa/pr23109.c
    trunk/gcc/testsuite/gcc.dg/tree-ssa/recip-3.c
    trunk/gcc/testsuite/gcc.dg/tree-ssa/recip-4.c
    trunk/gcc/testsuite/gcc.dg/tree-ssa/recip-5.c
    trunk/gcc/testsuite/gcc.dg/tree-ssa/recip-6.c
    trunk/gcc/testsuite/gcc.dg/tree-ssa/recip-7.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/Makefile.in
    trunk/gcc/doc/tm.texi
    trunk/gcc/passes.c
    trunk/gcc/target-def.h
    trunk/gcc/target.h
    trunk/gcc/targhooks.c
    trunk/gcc/targhooks.h
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gcc.dg/tree-ssa/pr23234.c
    trunk/gcc/testsuite/gcc.dg/tree-ssa/recip-2.c
    trunk/gcc/tree-cfg.c
    trunk/gcc/tree-flow.h
    trunk/gcc/tree-ssa-math-opts.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23109

[Bug tree-optimization/23109] [4.1 Regression] compiler generates wrong code leading to spurious division by zero with -funsafe-math-optimizations (instead of -ftrapping-math)

[bonzini at gcc dot gnu dot org]

------- Comment #16 from bonzini at gnu dot org  2006-01-11 14:29 -------
Subject: Bug 23109

Author: bonzini
Date: Wed Jan 11 14:29:29 2006
New Revision: 109586

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=109586
Log:
gcc:
2006-01-11  Paolo Bonzini  <bonzini@gnu.org>

        PR tree-optimization/23109
        PR tree-optimization/23948
        PR tree-optimization/24123

        * Makefile.in (tree-ssa-math-opts.o): Adjust dependencies.
        * tree-cfg.c (single_noncomplex_succ): New.
        * tree-flow.h (single_noncomplex_succ): Declare it.
        * tree-ssa-math-opts.c (enum place_reciprocal): Remove.
        * tree-ssa-math-opts.c (enum place_reciprocal): Remove.
        (struct occurrence, occ_head, occ_pool, is_divide_by, compute_merit,
        insert_bb, register_division_in, insert_reciprocals,
        replace_reciprocal, free_bb): New.
        (execute_cse_reciprocals_1): Rewritten.
        (execute_cse_reciprocals): Adjust calls to execute_cse_reciprocals_1.
        Do not commit any edge insertion.  Always compute dominators and
        create the allocation pool.
        * target-def.h (TARGET_MIN_DIVISIONS_FOR_RECIP_MUL): New.
        * target.h (struct gcc_target): Add min_divistions_for_recip_mul.
        * targhooks.c (default_min_divistions_for_recip_mul): New.
        * targhooks.h (default_min_divistions_for_recip_mul): New prototype.
        * passes.c (init_optimization_passes): Run recip after tree loop
        optimizations.
        * doc/tm.texi (Misc): Document TARGET_MIN_DIVISIONS_FOR_RECIP_MUL.

gcc/testsuite:
2006-01-11  Paolo Bonzini  <bonzini@gnu.org>

        PR tree-optimization/23109
        PR tree-optimization/23948
        PR tree-optimization/24123

        * gcc.dg/tree-ssa/recip-3.c, gcc.dg/tree-ssa/recip-4.c,
        gcc.dg/tree-ssa/recip-5.c, gcc.dg/tree-ssa/recip-6.c,
        gcc.dg/tree-ssa/recip-7.c, gcc.dg/tree-ssa/pr23109.c,
        g++.dg/tree-ssa/pr23948.C: New testcases.
        * gcc.dg/tree-ssa/recip-2.c, gcc.dg/tree-ssa/pr23234.c: Provide
        three divisions in order to do the optimization.


Added:
    branches/gcc-4_1-branch/gcc/testsuite/g++.dg/tree-ssa/pr23948.C
      - copied unchanged from r109578,
trunk/gcc/testsuite/g++.dg/tree-ssa/pr23948.C
    branches/gcc-4_1-branch/gcc/testsuite/gcc.dg/tree-ssa/pr23109.c
      - copied unchanged from r109578,
trunk/gcc/testsuite/gcc.dg/tree-ssa/pr23109.c
    branches/gcc-4_1-branch/gcc/testsuite/gcc.dg/tree-ssa/recip-3.c
      - copied unchanged from r109578,
trunk/gcc/testsuite/gcc.dg/tree-ssa/recip-3.c
    branches/gcc-4_1-branch/gcc/testsuite/gcc.dg/tree-ssa/recip-4.c
      - copied unchanged from r109578,
trunk/gcc/testsuite/gcc.dg/tree-ssa/recip-4.c
    branches/gcc-4_1-branch/gcc/testsuite/gcc.dg/tree-ssa/recip-5.c
      - copied unchanged from r109578,
trunk/gcc/testsuite/gcc.dg/tree-ssa/recip-5.c
    branches/gcc-4_1-branch/gcc/testsuite/gcc.dg/tree-ssa/recip-6.c
      - copied unchanged from r109578,
trunk/gcc/testsuite/gcc.dg/tree-ssa/recip-6.c
    branches/gcc-4_1-branch/gcc/testsuite/gcc.dg/tree-ssa/recip-7.c
      - copied unchanged from r109578,
trunk/gcc/testsuite/gcc.dg/tree-ssa/recip-7.c
Modified:
    branches/gcc-4_1-branch/gcc/ChangeLog
    branches/gcc-4_1-branch/gcc/Makefile.in
    branches/gcc-4_1-branch/gcc/doc/tm.texi
    branches/gcc-4_1-branch/gcc/passes.c
    branches/gcc-4_1-branch/gcc/target-def.h
    branches/gcc-4_1-branch/gcc/target.h
    branches/gcc-4_1-branch/gcc/targhooks.c
    branches/gcc-4_1-branch/gcc/targhooks.h
    branches/gcc-4_1-branch/gcc/testsuite/ChangeLog
    branches/gcc-4_1-branch/gcc/testsuite/gcc.dg/tree-ssa/pr23234.c
    branches/gcc-4_1-branch/gcc/testsuite/gcc.dg/tree-ssa/recip-2.c
    branches/gcc-4_1-branch/gcc/tree-cfg.c
    branches/gcc-4_1-branch/gcc/tree-flow.h
    branches/gcc-4_1-branch/gcc/tree-ssa-math-opts.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23109

[Bug tree-optimization/23109] [4.1 Regression] compiler generates wrong code leading to spurious division by zero with -funsafe-math-optimizations (instead of -ftrapping-math)

[bonzini at gnu dot org]

------- Comment #17 from bonzini at gnu dot org  2006-01-11 14:30 -------
patch committed to 4.1 too


-- 

bonzini at gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23109

[Bug c/23109] New: compiler generates wrong code leading to spurious division by zero

[p dot van-hoof at qub dot ac dot uk]

The attached code crashes on a division by zero when compiled as follows:

dogbert> gcc -O1 -funsafe-math-optimizations -ftrapping-math b.c
dogbert> a.out
Floating exception
dogbert> gcc -v
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with: ../gcc/configure --prefix=/usr/local/gcc410
--enable-languages=c,c++,f95
Thread model: posix
gcc version 4.1.0 20050725 (experimental)

I don't believe that -funsafe-math-optimizations enables -fno-trapping-math, but
to be really sure I added the -ftrapping-math command line option. It makes no
difference.

Taken at face value it looks like the optimizer lifts the division by d outside
the conditional on line 19, even though that could lead to a spurious division
by zero and -ftrapping-math is in effect.

This behavior only shows up on the mainline, and not on the 3.4 and 4.0
branches. A slightly modified version (to enable FP traps on Suns) also crashes
with gcc 4.1.0 on the target sparc-sun-solaris2.9.

-- 
           Summary: compiler generates wrong code leading to spurious
                    division by zero
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: p dot van-hoof at qub dot ac dot uk
                CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23109

[Bug tree-optimization/23109] [4.1 Regression] compiler generates wrong code leading to spurious division by zero with -funsafe-math-optimizations (instead of -ftrapping-math)

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |minor
          Component|c                           |tree-optimization
            Summary|compiler generates wrong    |[4.1 Regression] compiler
                   |code leading to spurious    |generates wrong code leading
                   |division by zero            |to spurious division by zero
                   |                            |with -funsafe-math-
                   |                            |optimizations (instead of -
                   |                            |ftrapping-math)
   Target Milestone|---                         |4.1.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23109

[Bug tree-optimization/23109] [4.1 Regression] compiler generates wrong code leading to spurious division by zero with -funsafe-math-optimizations (instead of -ftrapping-math)

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2005-08-01 08:53 -------
Subject: Bug 23109

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	rguenth@gcc.gnu.org	2005-08-01 08:53:00

Modified files:
	gcc            : ChangeLog tree-ssa-loop-im.c 
	                 tree-ssa-math-opts.c 

Log message:
	2005-08-01  Richard Guenther  <rguenther@suse.de>
	
	PR tree-optimization/23109
	* tree-ssa-math-opts.c (execute_cse_reciprocals_1):
	If trapping math is in effect, use post-dominator information
	to check if we'd in any case reach a trapping point before
	doing the reciprocal insertion.
	(execute_cse_reciprocals): Compute post-dominators, if necessary.
	* tree-ssa-loop-im.c (determine_invariantness_stmt): RDIV
	expressions are invariant only if trapping math is not in effect.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&r1=2.9622&r2=2.9623
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/tree-ssa-loop-im.c.diff?cvsroot=gcc&r1=2.48&r2=2.49
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/tree-ssa-math-opts.c.diff?cvsroot=gcc&r1=2.2&r2=2.3



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23109

[Bug tree-optimization/23109] [4.1 Regression] compiler generates wrong code leading to spurious division by zero with -funsafe-math-optimizations (instead of -ftrapping-math)

[rguenth at gcc dot gnu dot org]

------- Additional Comments From rguenth at gcc dot gnu dot org  2005-08-01 08:54 -------
Fixed.

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23109