From 1d5ba3bb5a3f55e10db05219638cfcd967d65417 Mon Sep 17 00:00:00 2001 From: Szabolcs Nagy Date: Sat, 18 May 2013 12:34:00 +0000 Subject: math: tan cleanups * use unsigned arithmetics on the representation * store arg reduction quotient in unsigned (so n%2 would work like n&1) * use different convention to pass the arg reduction bit to __tan (this argument used to be 1 for even and -1 for odd reduction which meant obscure bithacks, the new n&1 is cleaner) * raise inexact and underflow flags correctly for small x (tanl(x) may still raise spurious underflow for small but normal x) (this exception raising code increases codesize a bit, similar fixes are needed in many other places, it may worth investigating at some point if the inexact and underflow flags are worth raising correctly as this is not strictly required by the standard) * tanf manual reduction optimization is kept for now * tanl code path is cleaned up to follow similar logic to tan and tanf --- src/math/tanf.c | 32 +++++++++++++++++--------------- 1 file changed, 17 insertions(+), 15 deletions(-) (limited to 'src/math/tanf.c') diff --git a/src/math/tanf.c b/src/math/tanf.c index 8b0dfb20..aba19777 100644 --- a/src/math/tanf.c +++ b/src/math/tanf.c @@ -26,37 +26,39 @@ t4pio2 = 4*M_PI_2; /* 0x401921FB, 0x54442D18 */ float tanf(float x) { double y; - int32_t n, hx, ix; + uint32_t ix; + unsigned n, sign; - GET_FLOAT_WORD(hx, x); - ix = hx & 0x7fffffff; + GET_FLOAT_WORD(ix, x); + sign = ix >> 31; + ix &= 0x7fffffff; if (ix <= 0x3f490fda) { /* |x| ~<= pi/4 */ - if (ix < 0x39800000) /* |x| < 2**-12 */ - /* return x and raise inexact if x != 0 */ - if ((int)x == 0) - return x; - return __tandf(x, 1); + if (ix < 0x39800000) { /* |x| < 2**-12 */ + /* raise inexact if x!=0 and underflow if subnormal */ + FORCE_EVAL(ix < 0x00800000 ? x/0x1p120f : x+0x1p120f); + return x; + } + return __tandf(x, 0); } if (ix <= 0x407b53d1) { /* |x| ~<= 5*pi/4 */ if (ix <= 0x4016cbe3) /* |x| ~<= 3pi/4 */ - return __tandf((hx > 0 ? x-t1pio2 : x+t1pio2), -1); + return __tandf((sign ? x+t1pio2 : x-t1pio2), 1); else - return __tandf((hx > 0 ? x-t2pio2 : x+t2pio2), 1); + return __tandf((sign ? x+t2pio2 : x-t2pio2), 0); } if (ix <= 0x40e231d5) { /* |x| ~<= 9*pi/4 */ if (ix <= 0x40afeddf) /* |x| ~<= 7*pi/4 */ - return __tandf((hx > 0 ? x-t3pio2 : x+t3pio2), -1); + return __tandf((sign ? x+t3pio2 : x-t3pio2), 1); else - return __tandf((hx > 0 ? x-t4pio2 : x+t4pio2), 1); + return __tandf((sign ? x+t4pio2 : x-t4pio2), 0); } /* tan(Inf or NaN) is NaN */ if (ix >= 0x7f800000) return x - x; - /* general argument reduction needed */ + /* argument reduction */ n = __rem_pio2f(x, &y); - /* integer parameter: n even: 1; n odd: -1 */ - return __tandf(y, 1-((n&1)<<1)); + return __tandf(y, n&1); } -- cgit v1.2.1