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* optimize x86 feclearexceptRich Felker2012-03-171-16/+20
| | | | | if all exception flags will be cleared, we can avoid the expensive store/reload of the environment and just use the fnclex instruction.
* minor 387 fenv optimizationsRich Felker2012-03-171-6/+5
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* fix i386 fegetround and make fesetround fasternsz2012-03-171-10/+10
| | | | | | | | | | | | | | | | | | | | | Note that the new fesetround has slightly different semantics: Storing the floating-point environment with fnstenv makes the next fldenv (or fldcw) "non-signaling", so unmasked and pending exceptions does not invoke the exception handler. (These are rare since exceptions are handled immediately and by default all exceptions are masked anyway. But if one manually unmasks an exception in the control word then either sets the corresponding exception flag in the status word or the execution of an exception raising floating-point operation gets interrupted then it may happen). So the old implementation did not trap in some rare cases where the new implementation traps. However POSIX does not specify anything like the x87 exception handling traps and the fnstenv/fldenv pair is significantly slower than the fnstcw/fldcw pair (new code is about 5x faster here and it's dominated by the function call overhead).
* use type directives for fenv asm functionsRich Felker2011-06-281-0/+7
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* fix fesetround - it was writing to status word instead of control wordRich Felker2011-06-131-3/+8
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* floating point environment, untestedRich Felker2011-06-121-0/+75
at present the i386 code does not support sse floating point, which is not part of the standard i386 abi. while it may be desirable to support it later, doing so will reduce performance and require some tricks to probe if sse support is present. this first commit is i386-only, but it should be trivial to port the asm to x86_64.