This is the mail archive of the gcc-bugs@gcc.gnu.org mailing list for the GCC project.

Index Nav:	[Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav:	[Date Prev] [Date Next]	[Thread Prev] [Thread Next]
Other format:	[Raw text]

optimization/8156: -mcpu=pentium4 generates wrong fp results in glibc-2.3

From: bregor at sf dot anu dot edu dot au
To: gcc-gnats at gcc dot gnu dot org
Date: 7 Oct 2002 03:04:04 -0000
Subject: optimization/8156: -mcpu=pentium4 generates wrong fp results in glibc-2.3
Reply-to: bregor at sf dot anu dot edu dot au

>Number:         8156
>Category:       optimization
>Synopsis:       -mcpu=pentium4 generates wrong fp results in glibc-2.3
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Sun Oct 06 20:06:01 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     Roger Brown
>Release:        gcc (GCC) 3.2.1 20021004 (prerelease)
>Organization:
>Environment:
Linux-2.4.19-pre10
HJL's binutils-2.13.90.0.4 
glibc-2.3 release source code
>Description:
*** This may be a duplicate report but the original seems
    to have got lost.

  After building the released source for glibc-2.3,
  with "gcc (GCC) 3.2.1 20021004 (prerelease)",  and the
  -mcpu=pentium4 -march=pentium4 switches, make check
 discovered many serious errors for the floating-point
 special functions (see below).  The same build, with
  -mcpu=i686 -march=i686 failed with an assembler error.
  With -mcpu and -march left at the default values, both
  the build and check are clean.

  Other software details: O/S linux-2.4.19-pre10 and
  HJL's Linux-binutils-2.13.90.0.4.

  The actual "check" failure was:

GCONV PATH=/Main/Glibc/glibc-2.3/Build/iconvdata LC ALL=C
/Main/Glibc/glibc-2.3/Build/elf/ld-linux.so.2 --library-path
/Main/Glibc/glibc-2.3/Build:/Main/Glibc/glibc-2.3/Build/math:
/Main/Glibc/glibc-2.3/Build/elf:/Main/Glibc/glibc-2.3/Build/dlfcn:
/Main/Glibc/glibc-2.3/Build/nss:/Main/Glibc/glibc-2.3/Build/nis:
/Main/Glibc/glibc-2.3/Build/rt:/Main/Glibc/glibc-2.3/Build/resolv:
/Main/Glibc/glibc-2.3/Build/crypt:/Main/Glibc/glibc-2.3/Build/linuxthreads
/Main/Glibc/glibc-2.3/Build/math/test-idouble  >
/Main/Glibc/glibc-2.3/Build/math/test-idouble.out
make[2]: *** [/Main/Glibc/glibc-2.3/Build/math/test-idouble.out] Error 139

 The errors reported in test-idouble.out are alarming !
 The first part reads:

testing double (without inline functions)
Failure: Test: cosh (0.75) == 1.29468328467684468784170818539018176
Result:
 is:          2.11700001661267478426e+00   0x1.0ef9db467dcf80000000p+1
 should be:   1.29468328467684479222e+00   0x1.4b705d1e5d6a80000000p+0
 difference:  8.22316731935829992040e-01   0x1.a506b2dd3c6900000000p-1
 ulp       :  3703385327526728.0000
 max.ulp   :  0.0000
Maximal error of `cosh'
 is      : 3703385327526728 ulp
 accepted: 0 ulp
Failure: sinh (-inf) == -inf: Exception "Invalid operation" set
Failure: Test: sinh (-inf) == -inf
Result:
 is:          nan   nan
 should be:  -inf  -inf
Failure: Test: sinh (0.75) == 0.822316731935829980703661634446913849

  and it gets much worse, much worse !!

 Specific *.i files etc can be provided.
>How-To-Repeat:
Build glibc-2.3 with  -mcpu=pentium4  -march=pentium4
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:

Index Nav:	[Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav:	[Date Prev] [Date Next]	[Thread Prev] [Thread Next]