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

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>

diff --git a/tools/regression/lib/msun/test-fenv.c b/tools/regression/lib/msun/test-fenv.c
index 71e8eedb3bc98d8a33bda46b3261dde7a19c107a..0ea6e42a7c8b7e2829202778e89ec8f2b552a9b9 100644 (file)
--- a/tools/regression/lib/msun/test-fenv.c
+++ b/tools/regression/lib/msun/test-fenv.c
@@ -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);
 }