Date: Sat, 19 Sep 2020 17:25:06 -0700 From: Steve Kargl <sgk@troutmask.apl.washington.edu> To: freebsd-hackers@freebsd.org, freebsd-current@freebsd.org Subject: [PATCH] libm -- optimize __ldexp_cexp[f] Message-ID: <20200920002506.GA47948@troutmask.apl.washington.edu>
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The following patch is an opimization for he kernels used by cexp(x) and cexpf(x). . Use sincos[f] instead of a call to cos[f] and a call to sin[f]. . While here, alphabetize declaration. --- /usr/src/lib/msun/src/k_exp.c 2019-02-23 07:45:03.879997000 -0800 +++ src/k_exp.c 2019-12-26 08:15:30.109189000 -0800 @@ -88,7 +88,7 @@ double complex __ldexp_cexp(double complex z, int expt) { - double x, y, exp_x, scale1, scale2; + double c, exp_x, s, scale1, scale2, x, y; int ex_expt, half_expt; x = creal(z); @@ -105,6 +105,7 @@ half_expt = expt - half_expt; INSERT_WORDS(scale2, (0x3ff + half_expt) << 20, 0); - return (CMPLX(cos(y) * exp_x * scale1 * scale2, - sin(y) * exp_x * scale1 * scale2)); + sincos(y, &s, &c); + return (CMPLX(c * exp_x * scale1 * scale2, + s * exp_x * scale1 * scale2)); } --- /usr/src/lib/msun/src/k_expf.c 2019-02-23 07:45:03.881215000 -0800 +++ src/k_expf.c 2019-12-26 08:15:30.109818000 -0800 @@ -71,7 +71,7 @@ float complex __ldexp_cexpf(float complex z, int expt) { - float x, y, exp_x, scale1, scale2; + float c, exp_x, s, scale1, scale2, x, y; int ex_expt, half_expt; x = crealf(z); @@ -84,6 +84,7 @@ half_expt = expt - half_expt; SET_FLOAT_WORD(scale2, (0x7f + half_expt) << 23); - return (CMPLXF(cosf(y) * exp_x * scale1 * scale2, - sinf(y) * exp_x * scale1 * scale2)); + sincosf(y, &s, &c); + return (CMPLXF(c * exp_x * scale1 * scale2, + s * exp_x * scale1 * scale2)); } -- Steve
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