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| Rev | Author | Line No. | Line |
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| 3362 | Serge | 1 | /* |
| 2 | * ==================================================== |
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| 3 | * Copyright (C) 1998, 2002 by Red Hat Inc. All rights reserved. |
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| 4 | * |
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| 5 | * Permission to use, copy, modify, and distribute this |
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| 6 | * software is freely granted, provided that this notice |
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| 7 | * is preserved. |
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| 8 | * ==================================================== |
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| 9 | */ |
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| 10 | |||
| 11 | #if !defined(_SOFT_FLOAT) |
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| 12 | |||
| 13 | /* |
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| 14 | Fast version of pow using Intel float instructions. |
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| 15 | |||
| 16 | float _f_powf (float x, float y); |
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| 17 | |||
| 18 | Function calculates x to power of y. |
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| 19 | The function optimizes the case where x is >0.0 and y is finite. |
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| 20 | In such a case, there is no error checking or setting of errno. |
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| 21 | All other cases defer to normal powf() function which will |
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| 22 | set errno as normal. |
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| 23 | */ |
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| 24 | |||
| 25 | #include |
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| 26 | #include |
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| 27 | #include "f_math.h" |
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| 28 | |||
| 29 | float _f_powf (float x, float y) |
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| 30 | { |
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| 31 | /* following sequence handles the majority of cases for pow() */ |
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| 32 | if (x > 0.0 && check_finitef(y)) |
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| 33 | { |
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| 34 | float result; |
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| 35 | /* calculate x ** y as 2 ** (y log2(x)). On Intel, can only |
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| 36 | raise 2 to an integer or a small fraction, thus, we have |
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| 37 | to perform two steps 2**integer portion * 2**fraction. */ |
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| 38 | asm ("fyl2x; fld %%st; frndint; fsub %%st,%%st(1);"\ |
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| 39 | "fxch; fchs; f2xm1; fld1; faddp; fxch; fld1; fscale; fstp %%st(1);"\ |
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| 40 | "fmulp" : "=t" (result) : "0" (x), "u" (y) : "st(1)" ); |
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| 41 | return result; |
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| 42 | } |
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| 43 | else /* all other strange cases, defer to normal pow() */ |
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| 44 | return powf (x,y); |
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| 45 | } |
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| 46 | |||
| 47 | #endif |