?? e_pow.s
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{ .mfi nop.m 999 fma.s1 POW_q = POW_Z3sq, POW_q, POW_Z3 nop.i 999};;// p8 TRUE ==> |Y(G + r)| >= 10// double// -2^10 -2^9 2^9 2^10// -----+-----+----+ ... +-----+-----+-----// p8 | p9 | p8// | | p10 | |// Form signexp of constants to indicate overflow{ .mfi mov pow_GR_big_pos = 0x103ff fma.s1 POW_ssq = POW_s, POW_s, f0 cmp.le p8,p9 = 10, pow_GR_true_exp_Y_Gpr}{ .mfi mov pow_GR_big_neg = 0x303ff fma.s1 POW_v4 = POW_s, POW_Q3, POW_Q2 andcm pow_GR_sign_Y_Gpr = pow_GR_signexp_Y_Gpr, pow_GR_17ones};;// Form big positive and negative constants to test for possible overflow{ .mfi setf.exp POW_big_pos = pow_GR_big_pos fma.s1 POW_v2 = POW_s, POW_Q1, POW_Q0_half(p9) cmp.le.unc p0,p10 = 9, pow_GR_true_exp_Y_Gpr}{ .mfb setf.exp POW_big_neg = pow_GR_big_neg fma.s1 POW_1ps = f1,f1,POW_s(p8) br.cond.spnt POW_OVER_UNDER_X_NOT_INF};;// f123 = f12*(e123+1) = f12*e123+f12{ .mfi nop.m 999 fma.s1 POW_f123 = POW_e123,POW_f12,POW_f12 nop.i 999};;{ .mfi nop.m 999 fma.s1 POW_T1T2 = POW_T1, POW_T2, f0 nop.i 999}{ .mfi nop.m 999 fma.s1 POW_v3 = POW_ssq, POW_Q4, POW_v4 cmp.ne p12,p13 = pow_GR_xneg_yodd, r0};;{ .mfi nop.m 999 fma.s1 POW_v21ps = POW_ssq, POW_v2, POW_1ps nop.i 999}{ .mfi nop.m 999 fma.s1 POW_s4 = POW_ssq, POW_ssq, f0 nop.i 999};;{ .mfi nop.m 999(p12) fnma.s1 POW_A = POW_2M, POW_f123, f0 nop.i 999}{ .mfi nop.m 999(p13) fma.s1 POW_A = POW_2M, POW_f123, f0 cmp.eq p14,p11 = r0,r0 // Initialize p14 on, p11 off};;{ .mfi nop.m 999 fmerge.s POW_abs_q = f0, POW_q // Form |q| so can test its size nop.i 999};;{ .mfi(p10) cmp.eq p0,p14 = r0,r0 // Turn off p14 if no overflow fma.s1 POW_es = POW_s4, POW_v3, POW_v21ps nop.i 999}{ .mfi nop.m 999 fma.s1 POW_A = POW_A, POW_T1T2, f0 nop.i 999};;{ .mfi// Test for |q| < 2^-63. If so then reverse last two steps of the result// to avoid monotonicity problems for results near 1.0 in round up/down/zero.// p11 will be set if need to reverse the order, p14 if not. nop.m 999(p10) fcmp.lt.s0 p11,p14 = POW_abs_q, POW_2toM63 // Test |q| <2^-63 nop.i 999};;.pred.rel "mutex",p11,p14{ .mfi nop.m 999(p14) fma.s1 POW_A = POW_A, POW_es, f0 nop.i 999}{ .mfi nop.m 999(p11) fma.s1 POW_A = POW_A, POW_q, POW_A nop.i 999};;// Dummy op to set inexact if |q| < 2^-63{ .mfi nop.m 999(p11) fma.d.s0 POW_tmp = POW_A, POW_q, POW_A nop.i 999};;{ .mfi nop.m 999(p14) fma.d.s0 f8 = POW_A, POW_q, POW_A nop.i 999}{ .mfb nop.m 999(p11) fma.d.s0 f8 = POW_A, POW_es, f0(p10) br.ret.sptk b0 // Exit main branch if no over/underflow};;// POSSIBLE_OVER_UNDER// p6 = TRUE ==> Y_Gpr negative// Result is already computed. We just need to know if over/underflow occurred.{ .mfb cmp.eq p0,p6 = pow_GR_sign_Y_Gpr, r0 nop.f 999(p6) br.cond.spnt POW_POSSIBLE_UNDER};;// POSSIBLE_OVER// We got an answer.// overflow is a possibility, not a certainty// We define an overflow when the answer with// WRE set// user-defined rounding mode// double// Largest double is 7FE (biased double)// 7FE - 3FF + FFFF = 103FE// Create + largest_double_plus_ulp// Create - largest_double_plus_ulp// Calculate answer with WRE set.// single// Largest single is FE (biased double)// FE - 7F + FFFF = 1007E// Create + largest_single_plus_ulp// Create - largest_single_plus_ulp// Calculate answer with WRE set.// Cases when answer is ldn+1 are as follows:// ldn ldn+1// --+----------|----------+------------// |// +inf +inf -inf// RN RN// RZ// Put in s2 (td set, wre set){ .mfi nop.m 999 fsetc.s2 0x7F,0x42 nop.i 999};;{ .mfi nop.m 999 fma.d.s2 POW_wre_urm_f8 = POW_A, POW_q, POW_A nop.i 999};;// Return s2 to default{ .mfi nop.m 999 fsetc.s2 0x7F,0x40 nop.i 999};;// p7 = TRUE ==> yes, we have an overflow{ .mfi nop.m 999 fcmp.ge.s1 p7, p8 = POW_wre_urm_f8, POW_big_pos nop.i 999};;{ .mfi nop.m 999(p8) fcmp.le.s1 p7, p0 = POW_wre_urm_f8, POW_big_neg nop.i 999};;{ .mbb(p7) mov pow_GR_tag = 24(p7) br.cond.spnt __libm_error_region // Branch if overflow br.ret.sptk b0 // Exit if did not overflow};;// Here if |y*log(x)| < 2^(-11)// pow(x,y) ~ exp(d) ~ 1 + d + 0.5*d^2 + Q1*d^3 + Q2*d^4, where d = y*log(x).align 32POW_NEAR_ONE:{ .mfi nop.m 999 fma.s1 POW_d2 = POW_d, POW_d, f0 nop.i 999};;{ .mfi nop.m 999 fma.s1 POW_poly_d_hi = POW_d, POW_Q0_half, f1 nop.i 999}{ .mfi nop.m 999 fma.s1 POW_poly_d_lo = POW_d, POW_Q2, POW_Q1 nop.i 999};;{ .mfi nop.m 999 fma.s1 POW_poly_d = POW_d2, POW_poly_d_lo, POW_poly_d_hi nop.i 999};;{ .mfb nop.m 999 fma.d.s0 f8 = POW_d, POW_poly_d, f1 br.ret.sptk b0 // exit function for arguments |y*log(x)| < 2^(-11)};;POW_POSSIBLE_UNDER:// We got an answer. input was < -2^9 but > -2^10 (double)// We got an answer. input was < -2^6 but > -2^7 (float)// underflow is a possibility, not a certainty// We define an underflow when the answer with// ftz set// is zero (tiny numbers become zero)// Notice (from below) that if we have an unlimited exponent range,// then there is an extra machine number E between the largest denormal and// the smallest normal.// So if with unbounded exponent we round to E or below, then we are// tiny and underflow has occurred.// But notice that you can be in a situation where we are tiny, namely// rounded to E, but when the exponent is bounded we round to smallest// normal. So the answer can be the smallest normal with underflow.// E// -----+--------------------+--------------------+-----// | | |// 1.1...10 2^-3fff 1.1...11 2^-3fff 1.0...00 2^-3ffe// 0.1...11 2^-3ffe (biased, 1)// largest dn smallest normal// Put in s2 (td set, ftz set){ .mfi nop.m 999 fsetc.s2 0x7F,0x41 nop.i 999};;{ .mfi nop.m 999 fma.d.s2 POW_ftz_urm_f8 = POW_A, POW_q, POW_A nop.i 999};;// Return s2 to default{ .mfi nop.m 999 fsetc.s2 0x7F,0x40 nop.i 999};;// p7 = TRUE ==> yes, we have an underflow{ .mfi nop.m 999 fcmp.eq.s1 p7, p0 = POW_ftz_urm_f8, f0 nop.i 999};;{ .mbb(p7) mov pow_GR_tag = 25(p7) br.cond.spnt __libm_error_region // Branch if underflow br.ret.sptk b0 // Exit if did not underflow};;POW_X_DENORM:// Here if x unorm. Use the NORM_X for getf instructions, and then back// to normal path{ .mfi getf.exp pow_GR_signexp_X = POW_NORM_X nop.f 999 nop.i 999};;{ .mmi getf.sig pow_GR_sig_X = POW_NORM_X;; and pow_GR_exp_X = pow_GR_signexp_X, pow_GR_17ones nop.i 999};;{ .mib sub pow_G
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