| File: | src/lib/libm/src/s_expm1f.c |
| Warning: | line 105, column 6 Value stored to 't' is never read |
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| 1 | /* s_expm1f.c -- float version of s_expm1.c. |
| 2 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
| 3 | */ |
| 4 | |
| 5 | /* |
| 6 | * ==================================================== |
| 7 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| 8 | * |
| 9 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
| 10 | * Permission to use, copy, modify, and distribute this |
| 11 | * software is freely granted, provided that this notice |
| 12 | * is preserved. |
| 13 | * ==================================================== |
| 14 | */ |
| 15 | |
| 16 | #include "math.h" |
| 17 | #include "math_private.h" |
| 18 | |
| 19 | static const volatile float huge = 1.0e+30, tiny = 1.0e-30; |
| 20 | |
| 21 | static const float |
| 22 | one = 1.0, |
| 23 | o_threshold = 8.8721679688e+01,/* 0x42b17180 */ |
| 24 | ln2_hi = 6.9313812256e-01,/* 0x3f317180 */ |
| 25 | ln2_lo = 9.0580006145e-06,/* 0x3717f7d1 */ |
| 26 | invln2 = 1.4426950216e+00,/* 0x3fb8aa3b */ |
| 27 | /* scaled coefficients related to expm1 */ |
| 28 | Q1 = -3.3333335072e-02, /* 0xbd088889 */ |
| 29 | Q2 = 1.5873016091e-03, /* 0x3ad00d01 */ |
| 30 | Q3 = -7.9365076090e-05, /* 0xb8a670cd */ |
| 31 | Q4 = 4.0082177293e-06, /* 0x36867e54 */ |
| 32 | Q5 = -2.0109921195e-07; /* 0xb457edbb */ |
| 33 | |
| 34 | float |
| 35 | expm1f(float x) |
| 36 | { |
| 37 | float y,hi,lo,c,t,e,hxs,hfx,r1; |
| 38 | int32_t k,xsb; |
| 39 | u_int32_t hx; |
| 40 | |
| 41 | GET_FLOAT_WORD(hx,x)do { ieee_float_shape_type gf_u; gf_u.value = (x); (hx) = gf_u .word; } while (0); |
| 42 | xsb = hx&0x80000000; /* sign bit of x */ |
| 43 | if(xsb==0) y=x; else y= -x; /* y = |x| */ |
| 44 | hx &= 0x7fffffff; /* high word of |x| */ |
| 45 | |
| 46 | /* filter out huge and non-finite argument */ |
| 47 | if(hx >= 0x4195b844) { /* if |x|>=27*ln2 */ |
| 48 | if(hx >= 0x42b17218) { /* if |x|>=88.721... */ |
| 49 | if(hx>0x7f800000) |
| 50 | return x+x; /* NaN */ |
| 51 | if(hx==0x7f800000) |
| 52 | return (xsb==0)? x:-1.0;/* exp(+-inf)={inf,-1} */ |
| 53 | if(x > o_threshold) return huge*huge; /* overflow */ |
| 54 | } |
| 55 | if(xsb!=0) { /* x < -27*ln2, return -1.0 with inexact */ |
| 56 | if(x+tiny<(float)0.0) /* raise inexact */ |
| 57 | return tiny-one; /* return -1 */ |
| 58 | } |
| 59 | } |
| 60 | |
| 61 | /* argument reduction */ |
| 62 | if(hx > 0x3eb17218) { /* if |x| > 0.5 ln2 */ |
| 63 | if(hx < 0x3F851592) { /* and |x| < 1.5 ln2 */ |
| 64 | if(xsb==0) |
| 65 | {hi = x - ln2_hi; lo = ln2_lo; k = 1;} |
| 66 | else |
| 67 | {hi = x + ln2_hi; lo = -ln2_lo; k = -1;} |
| 68 | } else { |
| 69 | k = invln2*x+((xsb==0)?(float)0.5:(float)-0.5); |
| 70 | t = k; |
| 71 | hi = x - t*ln2_hi; /* t*ln2_hi is exact here */ |
| 72 | lo = t*ln2_lo; |
| 73 | } |
| 74 | x = hi - lo; |
| 75 | c = (hi-x)-lo; |
| 76 | } |
| 77 | else if(hx < 0x33000000) { /* when |x|<2**-25, return x */ |
| 78 | t = huge+x; /* return x with inexact flags when x!=0 */ |
| 79 | return x - (t-(huge+x)); |
| 80 | } |
| 81 | else k = 0; |
| 82 | |
| 83 | /* x is now in primary range */ |
| 84 | hfx = (float)0.5*x; |
| 85 | hxs = x*hfx; |
| 86 | r1 = one+hxs*(Q1+hxs*(Q2+hxs*(Q3+hxs*(Q4+hxs*Q5)))); |
| 87 | t = (float)3.0-r1*hfx; |
| 88 | e = hxs*((r1-t)/((float)6.0 - x*t)); |
| 89 | if(k==0) return x - (x*e-hxs); /* c is 0 */ |
| 90 | else { |
| 91 | e = (x*(e-c)-c); |
| 92 | e -= hxs; |
| 93 | if(k== -1) return (float)0.5*(x-e)-(float)0.5; |
| 94 | if(k==1) { |
| 95 | if(x < (float)-0.25) return -(float)2.0*(e-(x+(float)0.5)); |
| 96 | else return one+(float)2.0*(x-e); |
| 97 | } |
| 98 | if (k <= -2 || k>56) { /* suffice to return exp(x)-1 */ |
| 99 | int32_t i; |
| 100 | y = one-(e-x); |
| 101 | GET_FLOAT_WORD(i,y)do { ieee_float_shape_type gf_u; gf_u.value = (y); (i) = gf_u .word; } while (0); |
| 102 | SET_FLOAT_WORD(y,i+(k<<23))do { ieee_float_shape_type sf_u; sf_u.word = (i+(k<<23) ); (y) = sf_u.value; } while (0); /* add k to y's exponent */ |
| 103 | return y-one; |
| 104 | } |
| 105 | t = one; |
Value stored to 't' is never read | |
| 106 | if(k<23) { |
| 107 | int32_t i; |
| 108 | SET_FLOAT_WORD(t,0x3f800000 - (0x1000000>>k))do { ieee_float_shape_type sf_u; sf_u.word = (0x3f800000 - (0x1000000 >>k)); (t) = sf_u.value; } while (0); /* t=1-2^-k */ |
| 109 | y = t-(e-x); |
| 110 | GET_FLOAT_WORD(i,y)do { ieee_float_shape_type gf_u; gf_u.value = (y); (i) = gf_u .word; } while (0); |
| 111 | SET_FLOAT_WORD(y,i+(k<<23))do { ieee_float_shape_type sf_u; sf_u.word = (i+(k<<23) ); (y) = sf_u.value; } while (0); /* add k to y's exponent */ |
| 112 | } else { |
| 113 | int32_t i; |
| 114 | SET_FLOAT_WORD(t,((0x7f-k)<<23))do { ieee_float_shape_type sf_u; sf_u.word = (((0x7f-k)<< 23)); (t) = sf_u.value; } while (0); /* 2^-k */ |
| 115 | y = x-(e+t); |
| 116 | y += one; |
| 117 | GET_FLOAT_WORD(i,y)do { ieee_float_shape_type gf_u; gf_u.value = (y); (i) = gf_u .word; } while (0); |
| 118 | SET_FLOAT_WORD(y,i+(k<<23))do { ieee_float_shape_type sf_u; sf_u.word = (i+(k<<23) ); (y) = sf_u.value; } while (0); /* add k to y's exponent */ |
| 119 | } |
| 120 | } |
| 121 | return y; |
| 122 | } |
| 123 | DEF_STD(expm1f)__asm__(".global " "expm1f" " ; " "expm1f" " = " "_libm_expm1f" ); |