[Qemu-devel] [Bug 1701835] Re: floating-point operation bugs in qemu-alpha

[Stefan Ring]

Run this:

#include <stdio.h>
#include <string.h>

double get_fpcr()
{
    double x;
    asm ("mf_fpcr %0": "=f" (x));
    return x;
}

int main()
{
    double fpcr = get_fpcr();
    unsigned long l;
    memcpy(&l, &fpcr, 8);
    printf("%016lx\n", l);
    return 0;
}

Under qemu-system-alpha I get 680e800000000000.

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https://bugs.launchpad.net/bugs/1701835

Title:
  floating-point operation bugs in qemu-alpha

Status in QEMU:
  New

Bug description:
  When running the gnulib testsuite, I'm seeing test failures in the tests for 
libm functions
    cbrt
    cbrtf
    ceil
    ceilf
    coshf
    exp2
    exp2f
    floor
    floorf
    fma
    fmaf
    fmal
    frexp
    frexpf
    hypot
    hypotf
    hypotl
    ilogb
    ilogbf
    isfinite
    isinf
    isnan
    isnand
    isnanf
    ldexp
    ldexpf
    ldexpl
    log1p
    log1pf
    log2
    log2f
    logb
    logbf
    logbl
    rint
    rintf
    rintl
    signbit
    sqrt
    sqrtf
    strtod
  that I don't see when running the same (statically linked) executables in a 
VM, through qemu-system-alpha.

  How to reproduce:
  - Using gnulib, run ./gnulib-tool --create-testdir --dir=../testdir-math 
--single-configure cbrt cbrtf ceil ceilf coshf exp2 exp2f float floor floorf 
fma fmaf fmal frexp frexpf hypot hypotf hypotl ilogb ilogbf isfinite isinf 
isnan isnand isnanf ldexp ldexpf ldexpl log1p log1pf log2 log2f logb logbf 
logbl math printf-frexp rint rintf rintl round roundf signbit sqrt sqrtf strtod 
trunc truncf
  - Copy the resulting directory to a VM running Linux 2.6.26 with 
qemu-system-alpha.
  - There, configure and build the package:
    mkdir build-native-static; cd build-native-static; ../configure 
CPPFLAGS="-Wall" LDFLAGS="-static"; make; make check
    Only 4 tests fail.
  - Copy the resulting binaries back to the original x86_64 machine.
  - Set environment variables for using qemu-alpha.
  - Here, 50 tests fail that did not fail originally:

  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-cbrt
  ../../gltests/test-cbrt.h:39: assertion 'err > - L_(4.0) * L_(16.0) / 
TWO_MANT_DIG && err < L_(4.0) * L_(16.0) / TWO_MANT_DIG' failed
  Aborted (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-ceil1
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-ceil2
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-ceilf1
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-ceilf2
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-coshf 
  ../../gltests/test-coshf.c:37: assertion 'y >= 1.1854652f && y <= 1.1854653f' 
failed
  Aborted (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-float
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-floor1
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-floor2
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-floorf1
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-floorf2
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-fma1   
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-fma2
  ../../gltests/test-fma2.h:116: assertion 'result == expected' failed
  Aborted (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-fmaf1
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-fmaf2
  ../../gltests/test-fma2.h:116: assertion 'result == expected' failed
  Aborted (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-fmal2
  ../../gltests/test-fma2.h:116: assertion 'result == expected' failed
  Aborted (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-frexp
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-frexpf
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-hypot 
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-hypotf
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-hypotl
  ../../gltests/test-hypot.h:41: assertion 'z == HUGEVAL' failed
  Aborted (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-ilogb 
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-ilogbf
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-isfinite
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-isinf   
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-isnan
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-isnand-nolibm
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-isnand       
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-isnanf-nolibm
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-isnanf       
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-ldexp 
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-ldexpf
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-ldexpl
  ../../gltests/test-ldexp.h:99: assertion 'y == expected' failed
  Aborted (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-log1p 
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-log1pf
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-log2  
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-log2f
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-logb 
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-logbf
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-math 
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-printf-frexp
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-rint        
  ../../gltests/test-rint.c:63: assertion 'rint (0.7) == 1.0' failed
  Aborted (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-rintf
  ../../gltests/test-rintf.c:63: assertion 'rintf (0.7f) == 1.0f' failed
  Aborted (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-rintl
  ../../gltests/test-rintl.c:68: assertion 'rintl (0.7L) == 1.0L' failed
  Aborted (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-round1
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-roundf1
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-signbit
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-sqrt   
  ../../gltests/test-sqrt.h:40: assertion 'err > - L_(16.0) / TWO_MANT_DIG && 
err < L_(16.0) / TWO_MANT_DIG' failed
  Aborted (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-trunc1
  Floating point exception (core dumped)
  $ ~/inst-qemu/2.9.0/bin/qemu-alpha test-truncf1
  Floating point exception (core dumped)

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