[Bug target/60562] New: ’4.9 Regression] FAIL: gcc.target/i386/excess-precision-3.c execution test on x86_64-apple-darwin13

[Bug target/60562] New: ’4.9 Regression] FAIL: gcc.target/i386/excess-precision-3.c execution test on x86_64-apple-darwin13

[dominiq at lps dot ens.fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60562

            Bug ID: 60562
           Summary: ’4.9 Regression] FAIL:
                    gcc.target/i386/excess-precision-3.c execution test on
                    x86_64-apple-darwin13
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dominiq at lps dot ens.fr
                CC: iains at gcc dot gnu.org, rth at gcc dot gnu.org
              Host: x86_64-apple-darwin1*
            Target: x86_64-apple-darwin1*
             Build: x86_64-apple-darwin1*

The test gcc.target/i386/excess-precision-3.c has started to fail at run time
on x86_64-apple-darwin1* between revisions r208581 (pass) and r208594 (fail).
AFAICT the only relevant changes in this range are in r208587.
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Subject: [Bug regression/60363] [4.9 Regression]: logical_op_short_circuit, gcc.dg/tree-ssa/ssa-dom-thread-4.c scan-tree-dump-times dom1 "Threaded" 4
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60363

--- Comment #8 from bin.cheng <amker.cheng at gmail dot com> ---
Here is the findings.
1) After patching 208165, there are two more jump threading opportunities for
dom1 pass. Jump threading is doing alright, the interesting thing is why there
is no such opportunities before patching. The two additional opportunities are
introduced after vrp1.
VRP1 dump without patch:
  <bb 2>:
  goto <bb 15>;

  <bb 3>:
  if (b_elt_11(D) != 0B)
    goto <bb 4>;
  else
    goto <bb 8>;

  <bb 4>:
  goto <bb 6>;

  <bb 5>:
  kill_elt_14 = kill_elt_2->next;

  <bb 6>:
  # kill_elt_2 = PHI <kill_elt_4(4), kill_elt_14(5)>
  if (kill_elt_2 != 0B)
    goto <bb 7>;
  else
    goto <bb 19>;

  <bb 7>:
  _12 = kill_elt_2->indx;
  _13 = b_elt_11(D)->indx;
  if (_12 < _13)
    goto <bb 5>;
  else
    goto <bb 18>;

  <bb 8>:
  # kill_elt_3 = PHI <kill_elt_4(3)>
  if (b_elt_11(D) != 0B)
    goto <bb 9>;
  else
    goto <bb 14>;

  <bb 9>:
  if (kill_elt_3 != 0B)
    goto <bb 10>;
  else
    goto <bb 14>;

  <bb 10>:
  # kill_elt_32 = PHI <kill_elt_3(9), kill_elt_39(18)>
  _15 = kill_elt_32->indx;
  _16 = b_elt_11(D)->indx;
  if (_15 == _16)
    goto <bb 11>;
  else
    goto <bb 14>;

  <bb 11>:
  if (a_elt_9(D) == 0B)
    goto <bb 13>;
  else
    goto <bb 12>;

  <bb 12>:
  _17 = a_elt_9(D)->indx;
  if (_16 <= _17)
    goto <bb 13>;
  else
    goto <bb 14>;

  <bb 13>:
  _20 = (int) changed_1;
  _25 = bitmap_elt_ior (dst_21(D), dst_elt_22(D), dst_prev_23(D), a_elt_9(D),
&tmp_elt, _20);
  changed_26 = (unsigned char) _25;
  tmp_elt ={v} {CLOBBER};

  <bb 14>:
  # changed_18 = PHI <changed_26(13), changed_1(8), changed_1(9),
changed_1(10), changed_1(12), changed_1(18), changed_1(19)>
  # kill_elt_33 = PHI <kill_elt_32(13), kill_elt_3(8), kill_elt_3(9),
kill_elt_32(10), kill_elt_32(12), kill_elt_39(18), kill_elt_35(19)>

  <bb 15>:
  # changed_1 = PHI <changed_18(14), 0(2)>
  # kill_elt_4 = PHI <kill_elt_33(14), kill_elt_7(D)(2)>
  if (a_elt_9(D) != 0B)
    goto <bb 3>;
  else
    goto <bb 16>;

  <bb 16>:
  if (b_elt_11(D) != 0B)
    goto <bb 3>;
  else
    goto <bb 17>;

  <bb 17>:
  # changed_6 = PHI <changed_1(16)>
  changed_28 = changed_6;
  return changed_28;

  <bb 18>:
  # kill_elt_39 = PHI <kill_elt_2(7)>
  if (b_elt_11(D) != 0B)
    goto <bb 10>;
  else
    goto <bb 14>;

  <bb 19>:
  # kill_elt_35 = PHI <0B(6)>
  goto <bb 14>;

VRP1 dump with patch:
   <bb 2>:
  goto <bb 15>;

  <bb 3>:
  if (b_elt_11(D) != 0B)
    goto <bb 4>;
  else
    goto <bb 8>;

  <bb 4>:
  # kill_elt_10 = PHI <kill_elt_4(3)>
  goto <bb 6>;

  <bb 5>:
  kill_elt_14 = kill_elt_2->next;

  <bb 6>:
  # kill_elt_2 = PHI <kill_elt_10(4), kill_elt_14(5)>
  if (kill_elt_2 != 0B)
    goto <bb 7>;
  else
    goto <bb 19>;

  <bb 7>:
  _12 = kill_elt_2->indx;
  _13 = b_elt_11(D)->indx;
  if (_12 < _13)
    goto <bb 5>;
  else
    goto <bb 20>;

  <bb 8>:
  # kill_elt_3 = PHI <kill_elt_4(3)>
  if (b_elt_11(D) != 0B)
    goto <bb 9>;
  else
    goto <bb 14>;

  <bb 9>:
  if (kill_elt_3 != 0B)
    goto <bb 10>;
  else
    goto <bb 14>;

  <bb 10>:
  # kill_elt_34 = PHI <kill_elt_3(9), kill_elt_37(20)>
  _15 = kill_elt_34->indx;
  _16 = b_elt_11(D)->indx;
  if (_15 == _16)
    goto <bb 11>;
  else
    goto <bb 14>;

  <bb 11>:
  if (a_elt_9(D) == 0B)
    goto <bb 13>;
  else
    goto <bb 12>;

  <bb 12>:
  _17 = a_elt_9(D)->indx;
  if (_16 <= _17)
    goto <bb 13>;
  else
    goto <bb 14>;

  <bb 13>:
  _20 = (int) changed_1;
  _25 = bitmap_elt_ior (dst_21(D), dst_elt_22(D), dst_prev_23(D), a_elt_9(D),
&tmp_elt, _20);
  changed_26 = (unsigned char) _25;
  tmp_elt ={v} {CLOBBER};

  <bb 14>:
  # changed_19 = PHI <changed_1(8), changed_1(18), changed_26(13),
changed_1(12), changed_1(10), changed_1(19), changed_1(20), changed_1(9)>
  # kill_elt_18 = PHI <kill_elt_3(8), 0B(18), kill_elt_34(13), kill_elt_34(12),
kill_elt_34(10), kill_elt_41(19), kill_elt_37(20), 0B(9)>

  <bb 15>:
  # changed_1 = PHI <changed_19(14), 0(2)>
  # kill_elt_4 = PHI <kill_elt_18(14), kill_elt_7(D)(2)>
  if (a_elt_9(D) != 0B)
    goto <bb 3>;
  else
    goto <bb 16>;

  <bb 16>:
  if (b_elt_11(D) != 0B)
    goto <bb 3>;
  else
    goto <bb 17>;

  <bb 17>:
  # changed_29 = PHI <changed_1(16)>
  changed_28 = changed_29;
  return changed_28;

  <bb 18>:
  goto <bb 14>;

  <bb 19>:
  # kill_elt_41 = PHI <0B(6)>
  if (b_elt_11(D) != 0B)
    goto <bb 18>;
  else
    goto <bb 14>;

  <bb 20>:
  # kill_elt_37 = PHI <kill_elt_2(7)>
  if (b_elt_11(D) != 0B)
    goto <bb 10>;
  else
    goto <bb 14>;

The problem part is as below:
  <bb 14>:
  # changed_19 = PHI <changed_1(8), changed_1(18), changed_26(13),
changed_1(12), changed_1(10), changed_1(19), changed_1(20), changed_1(9)>
  # kill_elt_18 = PHI <kill_elt_3(8), 0B(18), kill_elt_34(13), kill_elt_34(12),
kill_elt_34(10), kill_elt_41(19), kill_elt_37(20), 0B(9)>

...

  <bb 18>:
  goto <bb 14>;

  <bb 19>:
  # kill_elt_41 = PHI <0B(6)>
  if (b_elt_11(D) != 0B)
    goto <bb 18>;
  else
    goto <bb 14>;

Since PHI argument "kill_elt_41(19)" equals to "0B(18)", the bb18 is a
removable forward basic block. By removing bb18, bb19 can be simplified into a
single jump to bb14 too. This is exactly what GCC does without patch.

When CFGcleanup tries to remove bb18, it has to check that PHI arguments
"kill_elt_41(19)" and "0B(18)" are compatible. Unfortunately, CFGcleanup
doesn't evaluate value of ssa_name and it doesn't know that "kill_elt_41(19)"
equals to "0" along jump threading path "19->14".

Since jump threading is now a flow sensitive optimization, it knows very well
about that truth, so I come up below conclusion:
Jump threading adds PHI argument by copying existing one when duplicating basic
blocks along jump threading path. It’s very possible that a PHI argument has a
constant value along threading path, but jump threading doesn’t do any value
evaluation and just copies the ssa_name. If we copy the constant value instead
of ssa_name, cfgcleanup after jump threading can see more removable forward
basic blocks thus the issue is fixed.

For this specific case, jump threading should be able to add argument "0(19)"
rather than "kill_elt_41(19)" to bb14, like:
  <bb 14>:
  # changed_19 = PHI <changed_1(8), changed_1(18), changed_26(13),
changed_1(12), changed_1(10), changed_1(19), changed_1(20), changed_1(9)>
  # kill_elt_18 = PHI <kill_elt_3(8), 0B(18), kill_elt_34(13), kill_elt_34(12),
kill_elt_34(10), 0(19), kill_elt_37(20), 0B(9)>


I worked out a patch fixing the issue, will send it for review.
>From gcc-bugs-return-446664-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Tue Mar 18 10:11:58 2014
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From: "skrll at netbsd dot org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/60039] sh3 optimisation bug with -O2
Date: Tue, 18 Mar 2014 10:11:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id`039

--- Comment #8 from Nick Hudson <skrll at netbsd dot org> ---
On 03/18/14 02:34, kkojima at gcc dot gnu.org wrote:
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id`039
>
> --- Comment #7 from Kazumoto Kojima <kkojima at gcc dot gnu.org> ---
> Ugh, then this is an old problem and we've missed to give a correct
> clobber information to udivsi3_i1 insn for PIC.  Does the patch
> below fix the issue?
>
> --- gcc/config/sh/sh.md.orig    2013-09-13 17:38:22.000000000 +0900
> +++ gcc/config/sh/sh.md    2014-03-18 11:08:19.868887133 +0900
> @@ -2152,6 +2152,7 @@
>       (udiv:SI (reg:SI R4_REG) (reg:SI R5_REG)))
>      (clobber (reg:SI T_REG))
>      (clobber (reg:SI PR_REG))
> +   (clobber (reg:SI R1_REG))
>      (clobber (reg:SI R4_REG))
>      (use (match_operand:SI 1 "arith_reg_operand" "r"))]
>     "TARGET_SH1 && TARGET_DIVIDE_CALL_DIV1"
>
yes, this patch helps ld.elf_so.

I seem to have a different problem in libc now.

Thanks,
Nick

[Bug target/60562] [4.9 Regression] FAIL: gcc.target/i386/excess-precision-3.c execution test on x86_64-apple-darwin13

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60562

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.9.0
            Summary|’4.9 Regression] FAIL:      |[4.9 Regression] FAIL:
                   |gcc.target/i386/excess-prec |gcc.target/i386/excess-prec
                   |ision-3.c execution test on |ision-3.c execution test on
                   |x86_64-apple-darwin13       |x86_64-apple-darwin13
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From: "sworddragon2 at aol dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/55896] Annoying compiler warning
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idU896

--- Comment #3 from sworddragon2 at aol dot com ---
> why aren't you using strlen???

Because of this bug (if it should be still valid):
https://bugs.launchpad.net/ubuntu/+source/gcc-4.7/+bug/1035321

[Bug target/60562] [4.9 Regression] FAIL: gcc.target/i386/excess-precision-3.c execution test after r208587

[dominiq at lps dot ens.fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60562

Dominique d'Humieres <dominiq at lps dot ens.fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|x86_64-apple-darwin1*       |
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-03-18
               Host|x86_64-apple-darwin1*       |
            Summary|[4.9 Regression] FAIL:      |[4.9 Regression] FAIL:
                   |gcc.target/i386/excess-prec |gcc.target/i386/excess-prec
                   |ision-3.c execution test on |ision-3.c execution test
                   |x86_64-apple-darwin13       |after r208587
     Ever confirmed|0                           |1
              Build|x86_64-apple-darwin1*       |

--- Comment #1 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
Also seen on linux:

http://gcc.gnu.org/ml/gcc-regression/2014-03/msg00088.html

[Bug target/60562] [4.9 Regression] FAIL: gcc.target/i386/excess-precision-3.c execution test after r208587

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60562

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Reduced testcase:
int
main ()
{
  volatile int i1 = 0x40000001;
  if ((float)i1 != 0x1.0p30f)
    __builtin_abort ();
  return 0;
}

[Bug target/60562] [4.9 Regression] FAIL: gcc.target/i386/excess-precision-3.c execution test after r208587

[rth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60562

Richard Henderson <rth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |rth at gcc dot gnu.org

--- Comment #3 from Richard Henderson <rth at gcc dot gnu.org> ---
Mine.

[Bug target/60562] [4.9 Regression] FAIL: gcc.target/i386/excess-precision-3.c execution test after r208587

[rth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60562

--- Comment #6 from Richard Henderson <rth at gcc dot gnu.org> ---
Author: rth
Date: Tue Mar 18 20:24:29 2014
New Revision: 208666

URL: http://gcc.gnu.org/viewcvs?rev=208666&root=gcc&view=rev
Log:
PR target/60562

        * config/i386/i386.md (*float<SWI48><MODEF>2_sse): Check
    X87_ENABLE_FLOAT for alternative 0.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/i386/i386.md

[Bug target/60562] [4.9 Regression] FAIL: gcc.target/i386/excess-precision-3.c execution test after r208587

[rth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60562

Richard Henderson <rth at gcc dot gnu.org> changed:

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

--- Comment #7 from Richard Henderson <rth at gcc dot gnu.org> ---
Fixed.

[Bug target/60562] [4.9 Regression] FAIL: gcc.target/i386/excess-precision-3.c execution test after r208587

[dominiq at lps dot ens.fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60562

--- Comment #8 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
> Fixed.

Thanks for the quick fix!