The fpcr value seen in a process running in a VM comes from the Linux
kernel, file linux/arch/alpha/kernel/process.c, function flush_thread():
/* Arrange for each exec'ed process to start off with a clean slate
with respect to the FPU. This is all exceptions disabled. */
current_thread_info()->ieee_state = 0;
wrfpcr(FPCR_DYN_NORMAL | ieee_swcr_to_fpcr(0));
where FPCR_DYN_NORMAL is 0x2UL << 58 /* towards nearest */
Where do we go from here? As far as I understand, qemu-alpha ought to
initialize the DYN bits to FPCR_DYN_NORMAL. Where in the code should
this be done? I see code in target/alpha/cpu.c, function
alpha_cpu_initfn, that initializes the DYN bits to FPCR_DYN_NORMAL. Is
this at the wrong place? Is it insufficient for another reason?
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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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