[Bug tree-optimization/33299] New: miscompilation with gfortran -O2 -ffast-math -ftree-vectorize

[Bug tree-optimization/33299] New: miscompilation with gfortran -O2 -ffast-math -ftree-vectorize

[jpr at csc dot fi]

The following gets miscompiled with gcc 4.3, works with 4.2.0 & 4.2.1 at least.

PROGRAM test
  REAL(8) :: f,dist(2)
  dist = [1.0_8, 0.5_8]
  PRINT*,f(1.0_8, dist), ' should be: ', MINVAL(dist)
END PROGRAM test

FUNCTION f( x, dist ) RESULT(s)
  REAL(8) :: dist(2), x, s
  s = MINVAL(dist)
  IF( x < 0 ) s = -s
END FUNCTION f



gfortran -v -O2 -ffast-math -ftree-vectorize -o test test.f90
Driving: gfortran -v -O2 -ffast-math -ftree-vectorize -o test test.f90
-lgfortranbegin -lgfortra n -lm -shared-libgcc
Using built-in specs.
Target: x86_64-unknown-linux-gnu
Configured with: /projects/tob/gcc/configure --enable-languages=c,fortran
--prefix=/projects/tob /gcc-trunk
Thread model: posix
gcc version 4.3.0 20070904 (experimental) [trunk revision 128067] (GCC)
COLLECT_GCC_OPTIONS='-v' '-O2' '-ffast-math' '-ftree-vectorize' '-o' 'test'
'-shared-libgcc' '-m tune=generic'
 /wrk/jpr/gcc-trunk/bin/../libexec/gcc/x86_64-unknown-linux-gnu/4.3.0/f951
test.f90 -quiet -dump base test.f90 -mtune=generic -auxbase test -O2 -version
-ffast-math -ftree-vectorize -fintrinsic -modules-path
/wrk/jpr/gcc-trunk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.3.0/finclude -o
/tmp/ jpr/ccEvFIMX.s
GNU F95 (GCC) version 4.3.0 20070904 (experimental) [trunk revision 128067]
(x86_64-unknown-linu x-gnu)
        compiled by GNU C version 4.3.0 20070904 (experimental) [trunk revision
128067], GMP ver sion 4.2.1, MPFR version 2.2.1.
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
COLLECT_GCC_OPTIONS='-v' '-O2' '-ffast-math' '-ftree-vectorize' '-o' 'test'
'-shared-libgcc' '-m tune=generic'
 as -V -Qy -o /tmp/jpr/ccJEvzPa.o /tmp/jpr/ccEvFIMX.s
GNU assembler version 2.15.92.0.2 (x86_64-redhat-linux) using BFD version
2.15.92.0.2 20040927
COMPILER_PATH=/wrk/jpr/gcc-trunk/bin/../libexec/gcc/x86_64-unknown-linux-gnu/4.3.0/:/wrk/jpr/gcc
-trunk/bin/../libexec/gcc/
LIBRARY_PATH=/wrk/jpr/gcc-trunk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.3.0/:/wrk/jpr/gcc-trun
k/bin/../lib/gcc/:/v/linux26_x86_64/opt/papi/3.5.0/lib64/../lib64/:/wrk/jpr/gcc-trunk/bin/../lib
/gcc/x86_64-unknown-linux-gnu/4.3.0/../../../../lib64/:/lib/../lib64/:/usr/lib/../lib64/:/v/linu
x26_x86_64/opt/papi/3.5.0/lib64/:/wrk/jpr/gcc-trunk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.3.
0/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-O2' '-ffast-math' '-ftree-vectorize' '-o' 'test'
'-shared-libgcc' '-m tune=generic'
 /wrk/jpr/gcc-trunk/bin/../libexec/gcc/x86_64-unknown-linux-gnu/4.3.0/collect2
--eh-frame-hdr -m  elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o
test /usr/lib/../lib64/crt1.o /usr/li b/../lib64/crti.o
/wrk/jpr/gcc-trunk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.3.0/crtbegin.o -L
/wrk/jpr/gcc-trunk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.3.0
-L/wrk/jpr/gcc-trunk/bin/../lib /gcc
-L/v/linux26_x86_64/opt/papi/3.5.0/lib64/../lib64
-L/wrk/jpr/gcc-trunk/bin/../lib/gcc/x86_6
4-unknown-linux-gnu/4.3.0/../../../../lib64 -L/lib/../lib64 -L/usr/lib/../lib64
-L/v/linux26_x86 _64/opt/papi/3.5.0/lib64
-L/wrk/jpr/gcc-trunk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.3.0/../. ./..
/tmp/jpr/ccJEvzPa.o -lgfortranbegin -lgfortran -lm -lgcc_s -lgcc -lc -lgcc_s
-lgcc /wrk/jpr
/gcc-trunk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.3.0/crtfastmath.o
/wrk/jpr/gcc-trunk/bin/.. /lib/gcc/x86_64-unknown-linux-gnu/4.3.0/crtend.o
/usr/lib/../lib64/crtn.o

./test
   1.00000000000000       should be:   0.500000000000000

Regrads, Juha


-- 
           Summary: miscompilation with gfortran -O2 -ffast-math -ftree-
                    vectorize
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jpr at csc dot fi
  GCC host triplet: x86_64 linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33299

[Bug tree-optimization/33299] miscompilation with gfortran -O2 -ffast-math -ftree-vectorize

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2007-09-04 09:55 -------
Confirmed.  It looks like the vectorizer forgets to update the PHI node for
stmp_var:

<bb 5>:
  # vect_var_.32_31 = PHI <vect_var_.32_29(3)>
  # s_4 = PHI <s_2(3)>
  # s_10 = PHI <s_2(3)>
  stmp_var_.34_32 = BIT_FIELD_REF <vect_var_.32_31, 64, 0>;
  stmp_var_.34_33 = BIT_FIELD_REF <vect_var_.32_31, 64, 64>;
  stmp_var_.34_34 = MIN_EXPR <stmp_var_.34_33, stmp_var_.34_32>;
  D.1396_15 = *x_14(D);
  if (D.1396_15 < 0.0)
    goto <bb 6>;
  else
    goto <bb 7>;

<bb 6>:
  s_16 = -stmp_var_.34_34;

<bb 7>: 
  # s_1 = PHI <s_4(5), s_16(6)>
  return s_1;

s_4 should be stmp_var_.34_34 instead.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dorit at gcc dot gnu dot org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2007-09-04 09:55:14
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33299

[Bug tree-optimization/33299] [4.3 Regression] miscompilation with gfortran -O2 -ffast-math -ftree-vectorize

[rguenth at gcc dot gnu dot org]

-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code
      Known to work|                            |4.2.1
            Summary|miscompilation with gfortran|[4.3 Regression]
                   |-O2 -ffast-math -ftree-     |miscompilation with gfortran
                   |vectorize                   |-O2 -ffast-math -ftree-
                   |                            |vectorize
   Target Milestone|---                         |4.3.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33299

[Bug tree-optimization/33299] [4.3 Regression] miscompilation with gfortran -O2 -ffast-math -ftree-vectorize

[dorit at gcc dot gnu dot org]

------- Comment #2 from dorit at gcc dot gnu dot org  2007-09-04 11:44 -------
(In reply to comment #1)
> Confirmed.  It looks like the vectorizer forgets to update the PHI node for
> stmp_var:

yes. I suspect I didn't expect at the time that there would be two
loop-closed-ssa-form phi-nodes at the loop exit for s_3, so I probably update
just one of them (s_10) and not the other (s_4). This is how it looks before
vectorization:

<bb 7>:
  # s_4 = PHI <s_3(3)>
  # s_10 = PHI <s_3(3)>
  D.1368_15 = *x_14(D);
  if (D.1368_15 < 0.0)
    goto <bb 8>;
  else
    goto <bb 9>;

<bb 8>:
  s_16 = -s_10;

<bb 9>:
  # s_1 = PHI <s_4(7), s_16(8)>
  return s_1;

I'll prepare a fix.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33299

[Bug tree-optimization/33299] [4.3 Regression] miscompilation with gfortran -O2 -ffast-math -ftree-vectorize

[dorit at gcc dot gnu dot org]

-- 

dorit at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |dorit at gcc dot gnu dot org
                   |dot org                     |
             Status|NEW                         |ASSIGNED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33299

[Bug tree-optimization/33299] [4.3 Regression] miscompilation with gfortran -O2 -ffast-math -ftree-vectorize

[dorit at gcc dot gnu dot org]

------- Comment #3 from dorit at gcc dot gnu dot org  2007-09-04 19:11 -------
I'm testing this patch:

Index: tree-vect-transform.c
===================================================================
*** tree-vect-transform.c       (revision 128037)
--- tree-vect-transform.c       (working copy)
*************** vect_create_epilog_for_reduction (tree v
*** 1964,1969 ****
--- 1964,1971 ----
    tree operation = GIMPLE_STMT_OPERAND (stmt, 1);
    bool nested_in_vect_loop = false;
    int op_type;
+   VEC(tree,heap) *phis = NULL;
+   int i;

    if (nested_in_vect_loop_p (loop, stmt))
      {
*************** vect_finalize_reduction:
*** 2260,2270 ****
        epilog_stmt = build_gimple_modify_stmt (new_dest, expr);
        new_temp = make_ssa_name (new_dest, epilog_stmt);
        GIMPLE_STMT_OPERAND (epilog_stmt, 0) = new_temp;
- #if 0
-       bsi_insert_after (&exit_bsi, epilog_stmt, BSI_NEW_STMT);
- #else
        bsi_insert_before (&exit_bsi, epilog_stmt, BSI_SAME_STMT);
- #endif
      }


--- 2262,2268 ----
*************** vect_finalize_reduction:
*** 2274,2318 ****
       Find the loop-closed-use at the loop exit of the original scalar result.
       (The reduction result is expected to have two immediate uses - one at
the
       latch block, and one at the loop exit).  */
!   exit_phi = NULL;
    FOR_EACH_IMM_USE_FAST (use_p, imm_iter, scalar_dest)
      {
        if (!flow_bb_inside_loop_p (loop, bb_for_stmt (USE_STMT (use_p))))
        {
          exit_phi = USE_STMT (use_p);
!         break;
        }
      }
    /* We expect to have found an exit_phi because of loop-closed-ssa form.  */
!   gcc_assert (exit_phi);

!   if (nested_in_vect_loop)
      {
!       stmt_vec_info stmt_vinfo = vinfo_for_stmt (exit_phi);

!       /* FORNOW. Currently not supporting the case that an inner-loop
reduction
!        is not used in the outer-loop (but only outside the outer-loop).  */
!       gcc_assert (STMT_VINFO_RELEVANT_P (stmt_vinfo) 
!                 && !STMT_VINFO_LIVE_P (stmt_vinfo));
! 
!       epilog_stmt = adjustment_def ? epilog_stmt :  new_phi;
!       STMT_VINFO_VEC_STMT (stmt_vinfo) = epilog_stmt;
!       set_stmt_info (get_stmt_ann (epilog_stmt),
!                      new_stmt_vec_info (epilog_stmt, loop_vinfo));

!       if (vect_print_dump_info (REPORT_DETAILS))
!         {
!           fprintf (vect_dump, "vector of partial results after inner-loop:");
!           print_generic_expr (vect_dump, epilog_stmt, TDF_SLIM);
!         }
!       return;
      }
- 
-   /* Replace the uses:  */
-   orig_name = PHI_RESULT (exit_phi);
-   FOR_EACH_IMM_USE_STMT (use_stmt, imm_iter, orig_name)
-     FOR_EACH_IMM_USE_ON_STMT (use_p, imm_iter)
-       SET_USE (use_p, new_temp);
  } 


--- 2272,2313 ----
       Find the loop-closed-use at the loop exit of the original scalar result.
       (The reduction result is expected to have two immediate uses - one at
the 
       latch block, and one at the loop exit).  */
!   phis = VEC_alloc (tree, heap, 10);
    FOR_EACH_IMM_USE_FAST (use_p, imm_iter, scalar_dest)
      {
        if (!flow_bb_inside_loop_p (loop, bb_for_stmt (USE_STMT (use_p))))
        {
          exit_phi = USE_STMT (use_p);
!         VEC_quick_push (tree, phis, exit_phi);
        }
      }
    /* We expect to have found an exit_phi because of loop-closed-ssa form.  */
!   gcc_assert (!VEC_empty (tree, phis));

!   for (i = 0; VEC_iterate (tree, phis, i, exit_phi); i++)
      {
!       if (nested_in_vect_loop)
!       {
!         stmt_vec_info stmt_vinfo = vinfo_for_stmt (exit_phi);

!         /* FORNOW. Currently not supporting the case that an inner-loop
reduction
!            is not used in the outer-loop (but only outside the outer-loop). 
*/
!         gcc_assert (STMT_VINFO_RELEVANT_P (stmt_vinfo) 
!                     && !STMT_VINFO_LIVE_P (stmt_vinfo));
!
!         epilog_stmt = adjustment_def ? epilog_stmt :  new_phi;
!         STMT_VINFO_VEC_STMT (stmt_vinfo) = epilog_stmt;
!         set_stmt_info (get_stmt_ann (epilog_stmt),
!         new_stmt_vec_info (epilog_stmt, loop_vinfo));
!         continue;
!       }

!       /* Replace the uses:  */
!       orig_name = PHI_RESULT (exit_phi);
!       FOR_EACH_IMM_USE_STMT (use_stmt, imm_iter, orig_name)
!       FOR_EACH_IMM_USE_ON_STMT (use_p, imm_iter)
!         SET_USE (use_p, new_temp);
      }
  } 


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33299

[Bug tree-optimization/33299] [4.3 Regression] miscompilation with gfortran -O2 -ffast-math -ftree-vectorize

[dorit at gcc dot gnu dot org]

------- Comment #4 from dorit at gcc dot gnu dot org  2007-09-04 19:14 -------
(by the way, fast-math should not be required here, but that's a different
bug... will fix that soonish)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33299

[Bug tree-optimization/33299] [4.3 Regression] miscompilation with gfortran -O2 -ffast-math -ftree-vectorize

[mmitchel at gcc dot gnu dot org]

-- 

mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33299

[Bug tree-optimization/33299] [4.3 Regression] miscompilation with gfortran -O2 -ffast-math -ftree-vectorize

[dorit at gcc dot gnu dot org]

------- Comment #5 from dorit at gcc dot gnu dot org  2007-09-07 15:00 -------
Subject: Bug 33299

Author: dorit
Date: Fri Sep  7 15:00:11 2007
New Revision: 128242

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=128242
Log:
        PR tree-optimization/33299
        * tree-vect-transform.c (vect_create_epilog_for_reduction): Update uses
        for all relevant loop-exit phis, not just the first.


Added:
    trunk/gcc/testsuite/gfortran.dg/vect/fast-math-pr33299.f90
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gfortran.dg/vect/vect.exp
    trunk/gcc/tree-vect-transform.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33299

[Bug tree-optimization/33299] [4.3 Regression] miscompilation with gfortran -O2 -ffast-math -ftree-vectorize

[dorit at gcc dot gnu dot org]

------- Comment #6 from dorit at gcc dot gnu dot org  2007-09-08 09:24 -------
fix committed


-- 

dorit at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33299