[Bug middle-end/51867] New: GCC generates inconsistent code for same sources calling builtin calls, like sqrtf

[Bug middle-end/51867] New: GCC generates inconsistent code for same sources calling builtin calls, like sqrtf

[amker.cheng at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51867

             Bug #: 51867
           Summary: GCC generates inconsistent code for same sources
                    calling builtin calls, like sqrtf
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: trivial
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: amker.cheng@gmail.com


compile following program:
----------------------------------------------
#include <math.h>
int a(float x) {
     return sqrtf(x);
}
int b(float x) {
     return sqrtf(x);
}

With command:
arm-none-eabi-gcc -mthumb -mhard-float -mfpu=fpv4-sp-d16
-mcpu=cortex-m4 -O0 -S a.c -o a.S

The generated assembly codes is like:
----------------------------------------------
a:
       @ args = 0, pretend = 0, frame = 8
       @ frame_needed = 1, uses_anonymous_args = 0
       push    {r7, lr}
       sub     sp, sp, #8
       add     r7, sp, #0
       fsts    s0, [r7, #4]
       flds    s15, [r7, #4]
       fsqrts  s15, s15
       fcmps   s15, s15
       fmstat
       beq     .L2
       flds    s0, [r7, #4]
       bl      sqrtf
       fcpys   s15, s0
.L2:
       ftosizs s15, s15
       fmrs    r3, s15 @ int
       mov     r0, r3
       add     r7, r7, #8
       mov     sp, r7
       pop     {r7, pc}
       .size   a, .-a
       .align  2
       .global b
       .thumb
       .thumb_func
       .type   b, %function
b:
       @ args = 0, pretend = 0, frame = 8
       @ frame_needed = 1, uses_anonymous_args = 0
       push    {r7, lr}
       sub     sp, sp, #8
       add     r7, sp, #0
       fsts    s0, [r7, #4]
       flds    s0, [r7, #4]
       bl      sqrtf
       fcpys   s15, s0
       ftosizs s15, s15
       fmrs    r3, s15 @ int
       mov     r0, r3
       add     r7, r7, #8
       mov     sp, r7
       pop     {r7, pc}
       .size   b, .-b

The problem exists on trunk and triggered only by O0 optimization.
The problem stands for x86 target too.

[Bug middle-end/51867] GCC generates inconsistent code for same sources calling builtin calls, like sqrtf

[amker.cheng at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51867

--- Comment #1 from amker.cheng <amker.cheng at gmail dot com> 2012-01-16 10:15:59 UTC ---
The cause is in function expand_builtin, gcc checks following conditions:
----------------------------------------------
 /* When not optimizing, generate calls to library functions for a certain
    set of builtins.  */
 if (!optimize
     && !called_as_built_in (fndecl)
     && DECL_ASSEMBLER_NAME_SET_P (fndecl)
     && fcode != BUILT_IN_ALLOCA
     && fcode != BUILT_IN_ALLOCA_WITH_ALIGN
     && fcode != BUILT_IN_FREE)
   return expand_call (exp, target, ignore);

The control flow is:
1, DECL_ASSEMBLER_NAME_SET_P (fndecl) is false at the first time when compiling
a;
2, It is then set in following codes when expanding sqrtf call in function a;
3, When compiling function b, gcc checks DECL_ASSEMBLER_NAME_SET_P (fndecl)
    again and this time it's true;

[Bug middle-end/51867] GCC generates inconsistent code for same sources calling builtin calls, like sqrtf

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51867

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-01-16
     Ever Confirmed|0                           |1

--- Comment #2 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-01-16 14:33:58 UTC ---
Confirmed.  That check is definitely bogus.

[Bug middle-end/51867] GCC generates inconsistent code for same sources calling builtin calls, like sqrtf

[amker.cheng at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51867

--- Comment #3 from amker.cheng <amker.cheng at gmail dot com> 2012-01-17 10:35:14 UTC ---
test case c-c++-common/dfp/signbit-2.c depends on this check.
the case is like:
---------------------------------------------------------------------
/* { dg-options "-O0" } */

/* Check that the compiler uses builtins for signbit; if not the link
   will fail because library functions are in libm.  */

#include "dfp-dbg.h"

volatile _Decimal32 sd = 2.3df;
volatile _Decimal64 dd = -4.5dd;
volatile _Decimal128 tf = 5.3dl;
volatile float f = 1.2f;
volatile double d = -7.8;
volatile long double ld = 3.4L;

EXTERN int signbitf (float);
EXTERN int signbit (double);
EXTERN int signbitl (long double);
EXTERN int signbitd32 (_Decimal32);
EXTERN int signbitd64 (_Decimal64);
EXTERN int signbitd128 (_Decimal128);

int
main ()
{
  if (signbitf (f) != 0) FAILURE
  if (signbit (d) == 0) FAILURE
  if (signbitl (ld) != 0) FAILURE
  if (signbitd32 (sd) != 0) FAILURE
  if (signbitd64 (dd) == 0) FAILURE
  if (signbitd128 (tf) != 0) FAILURE

  FINISH
}

It is compiled without optimization and will fail if no builtin_* functions are
used.
Not sure it is intended or not.

[Bug middle-end/51867] GCC generates inconsistent code for same sources calling builtin calls, like sqrtf

[amker at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51867

--- Comment #4 from amker at gcc dot gnu.org 2012-02-09 09:37:43 UTC ---
Author: amker
Date: Thu Feb  9 09:37:37 2012
New Revision: 184037

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=184037
Log:

    PR target/51867
    * builtins.c (expand_builtin): Don't check DECL_ASSEMBLER_NAME_SET_P.

    PR target/51867
    * testsuite/c-c++-common/dfp/signbit-2.c: Change '-O0' to '-O1'.
    * testsuite/gcc.dg/pr51867.c: New test.


Added:
    trunk/gcc/testsuite/gcc.dg/pr51867.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/builtins.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/c-c++-common/dfp/signbit-2.c

[Bug middle-end/51867] GCC generates inconsistent code for same sources calling builtin calls, like sqrtf

[amker.cheng at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51867

--- Comment #5 from amker.cheng <amker.cheng at gmail dot com> 2012-06-18 02:03:21 UTC ---
Should be fixed.

[Bug middle-end/51867] GCC generates inconsistent code for same sources calling builtin calls, like sqrtf

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51867

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
           Keywords|                            |missed-optimization
         Resolution|---                         |FIXED
   Target Milestone|---                         |4.7.0

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Fixed.