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| /* -------------------------------------------------------------- */ |
| /* PROLOG END TAG zYx */ |
| #ifdef __SPU__ |
| |
| #ifndef _EXP2D2_H_ |
| #define _EXP2D2_H_ 1 |
| |
| #include <spu_intrinsics.h> |
| |
| |
| /* |
| * FUNCTION |
| * vector double _exp2d2(vector double x) |
| * |
| * DESCRIPTION |
| * _exp2d2 computes 2 raised to the input x for each |
| * of the double word elements of x. Computation is |
| * performed by observing the 2^(a+b) = 2^a * 2^b. |
| * We decompose x into a and b (above) by letting. |
| * a = ceil(x), b = x - a; |
| * |
| * 2^a is easily computed by placing a into the exponent |
| * or a floating point number whose mantissa is all zeros. |
| * |
| * 2^b is computed using the polynomial approximation. |
| * |
| * __13_ |
| * \ |
| * \ |
| * 2^x = / Ci*x^i |
| * /____ |
| * i=0 |
| * |
| * for x in the range 0.0 to 1.0. |
| * |
| */ |
| #define EXP_C00 1.0 |
| #define EXP_C01 6.93147180559945286227e-01 |
| #define EXP_C02 2.40226506959100694072e-01 |
| #define EXP_C03 5.55041086648215761801e-02 |
| #define EXP_C04 9.61812910762847687873e-03 |
| #define EXP_C05 1.33335581464284411157e-03 |
| #define EXP_C06 1.54035303933816060656e-04 |
| #define EXP_C07 1.52527338040598376946e-05 |
| #define EXP_C08 1.32154867901443052734e-06 |
| #define EXP_C09 1.01780860092396959520e-07 |
| #define EXP_C10 7.05491162080112087744e-09 |
| #define EXP_C11 4.44553827187081007394e-10 |
| #define EXP_C12 2.56784359934881958182e-11 |
| #define EXP_C13 1.36914888539041240648e-12 |
| |
| static __inline vector double _exp2d2(vector double vx) |
| { |
| vec_int4 ix, exp; |
| vec_uint4 overflow, underflow; |
| vec_float4 vxf; |
| vec_double2 p1, p2, x2, x4, x8; |
| vec_double2 vy, vxw, out_of_range; |
| |
| /* Compute: vxw = x - ceil(x) |
| */ |
| vxw = spu_add(vx, spu_splats(0.5)); |
| vxf = spu_roundtf(vxw); |
| ix = spu_convts(vxf, 0); |
| ix = spu_add(ix, (vec_int4)spu_andc(spu_cmpgt(spu_splats(0.0f), vxf), spu_cmpeq(ix, spu_splats((int)0x80000000)))); |
| vxf = spu_convtf(ix, 0); |
| vxw = spu_sub(vx, spu_extend(vxf)); |
| |
| /* Detect overflow and underflow. If overflow, force the result |
| * to infinity (at the end). |
| */ |
| exp = spu_shuffle(ix, ix, ((vec_uchar16) { 0,1,2,3, 0,1,2,3, 8,9,10,11, 8,9,10,11 })); |
| |
| overflow = spu_cmpgt(exp, 1023); |
| underflow = spu_cmpgt(exp, -1023); |
| out_of_range = (vec_double2)spu_and(overflow, ((vec_uint4) { 0x7FF00000, 0, 0x7FF00000, 0 })); |
| |
| /* Calculate the result by evaluating the 13th order polynomial. |
| * For efficiency, the polynomial is broken into two parts and |
| * evaluate then using nested |
| * |
| * result = (((((c13*x + c12)*x + c11)*x + c10)*x + c9)*x + c8)*x^8 + |
| * ((((((c7*x + c6)*x + c5)*x + c4)*x + c3)*x + c2)*x + c1)*x + c0 |
| */ |
| p2 = spu_madd(spu_splats(EXP_C07), vxw, spu_splats(EXP_C06)); |
| p1 = spu_madd(spu_splats(EXP_C13), vxw, spu_splats(EXP_C12)); |
| x2 = spu_mul(vxw, vxw); |
| p2 = spu_madd(vxw, p2, spu_splats(EXP_C05)); |
| p1 = spu_madd(vxw, p1, spu_splats(EXP_C11)); |
| x4 = spu_mul(x2, x2); |
| p2 = spu_madd(vxw, p2, spu_splats(EXP_C04)); |
| p1 = spu_madd(vxw, p1, spu_splats(EXP_C10)); |
| p2 = spu_madd(vxw, p2, spu_splats(EXP_C03)); |
| p1 = spu_madd(vxw, p1, spu_splats(EXP_C09)); |
| x8 = spu_mul(x4, x4); |
| p2 = spu_madd(vxw, p2, spu_splats(EXP_C02)); |
| p1 = spu_madd(vxw, p1, spu_splats(EXP_C08)); |
| p2 = spu_madd(vxw, p2, spu_splats(EXP_C01)); |
| p2 = spu_madd(vxw, p2, spu_splats(EXP_C00)); |
| vy = spu_madd(x8, p1, p2); |
| |
| /* Align the integer integer portion of x with the exponent. |
| */ |
| ix = spu_sl(ix, ((vec_uint4) { 20, 32, 20, 32 })); |
| vy = (vec_double2)spu_add((vec_int4)vy, ix); |
| |
| /* Select the result if not overflow or underflow. Otherwise select the |
| * the out of range value. |
| */ |
| return (spu_sel(vy, out_of_range, (vec_ullong2)spu_orc(overflow, underflow))); |
| } |
| |
| #endif /* _EXP2D2_H_ */ |
| #endif /* __SPU__ */ |