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linux: reset to extended-precision fp before calling pow()

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This commit is contained in:
Matthew Flatt 2011-01-04 16:13:02 -07:00
parent e88c2142e6
commit dd0b41d974
1 changed files with 32 additions and 9 deletions
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41
src/racket/src/number.c
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@ -192,6 +192,23 @@ READ_ONLY Scheme_Object *scheme_single_inf_object, *scheme_single_minus_inf_obje
#include <machine/fpu.h>
#endif
#ifdef ASM_DBLPREC_CONTROL_87
/* Linux uses extended precision by default.
Make x87 computations double-precision instead of
extended-precision, so that if/when the JIT generates
x87 instructions, it's consistent with everything else. */
static void to_double_prec(void)
{
int _dblprec = 0x27F;
asm ("fldcw %0" : : "m" (_dblprec));
}
static void to_extended_prec(void)
{
int _dblprec = 0x37F;
asm ("fldcw %0" : : "m" (_dblprec));
}
#endif
void
scheme_init_number (Scheme_Env *env)
{
@ -247,13 +264,7 @@ scheme_init_number (Scheme_Env *env)
}
#endif
#ifdef ASM_DBLPREC_CONTROL_87
{
/* Make x87 computations double-precision instead of
extended-precision, so that if/when the JIT generates
x87 instructions, it's consistent with everything else. */
int _dblprec = 0x27F;
asm ("fldcw %0" : : "m" (_dblprec));
}
to_double_prec();
#endif
END_XFORM_SKIP;
@ -2450,8 +2461,20 @@ static double sch_pow(double x, double y)
return scheme_infinity_val;
}
}
} else
return pow(x, y);
} else {
#ifdef ASM_DBLPREC_CONTROL_87
/* libm's pow() implementation seems to rely on
extended precision in pow(), so reset the control
word while calling pow(); note that the x87 control
word is thread-specific */
to_extended_prec();
#endif
x = pow(x, y);
#ifdef ASM_DBLPREC_CONTROL_87
to_double_prec();
#endif
return x;
}
}
#endif