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Fix test-fenv:test_dfl_env when run on some amd64 CPUs

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Compare the fields that the AMD [1] and Intel [2] specs say will be
set once fnstenv returns.

Not all amd64 capable processors zero out the env.__x87.__other field
(example: AMD Opteron 6308). The AMD64/x64 specs aren't explicit on what the
env.__x87.__other field will contain after fnstenv is executed, so the values
in env.__x87.__other could be filled with arbitrary data depending on how the
CPU-specific implementation of fnstenv.

1. http://support.amd.com/TechDocs/26569_APM_v5.pdf
2. http://www.intel.com/Assets/en_US/PDF/manual/253666.pdf

Discussed with: kib, Anton Rang <anton.rang@isilon.com>
Reviewed by: Daniel O'Connor <darius@dons.net.au> (earlier patch; pre-generalization)
MFC after: 1 week
Sponsored by: EMC / Isilon Storage Division
Reported by: Bill Morchin <wmorchin@isilon.com>
This commit is contained in:
Enji Cooper 2015-10-14 20:22:12 +00:00
parent b9b3f1e65a
commit d63d2d29cb
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=289332
1 changed files with 27 additions and 0 deletions
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27
tools/regression/lib/msun/test-fenv.c
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@ -133,7 +133,34 @@ test_dfl_env(void)
fenv_t env;
fegetenv(&env);
#ifdef __amd64__
/*
* Compare the fields that the AMD [1] and Intel [2] specs say will be
* set once fnstenv returns.
*
* Not all amd64 capable processors implement the fnstenv instruction
* by zero'ing out the env.__x87.__other field (example: AMD Opteron
* 6308). The AMD64/x64 specs aren't explicit on what the
* env.__x87.__other field will contain after fnstenv is executed, so
* the values in env.__x87.__other could be filled with arbitrary
* data depending on how the CPU implements fnstenv.
*
* 1. http://support.amd.com/TechDocs/26569_APM_v5.pdf
* 2. http://www.intel.com/Assets/en_US/PDF/manual/253666.pdf
*/
assert(memcmp(&env.__mxcsr, &FE_DFL_ENV->__mxcsr,
sizeof(env.__mxcsr)) == 0);
assert(memcmp(&env.__x87.__control, &FE_DFL_ENV->__x87.__control,
sizeof(env.__x87.__control)) == 0);
assert(memcmp(&env.__x87.__status, &FE_DFL_ENV->__x87.__status,
sizeof(env.__x87.__status)) == 0);
assert(memcmp(&env.__x87.__tag, &FE_DFL_ENV->__x87.__tag,
sizeof(env.__x87.__tag)) == 0);
#else
assert(memcmp(&env, FE_DFL_ENV, sizeof(env)) == 0);
#endif
#endif
assert(fetestexcept(FE_ALL_EXCEPT) == 0);
}