libclc: Update f64 log implementations (#186048)
The log implementation was originally ported from rocm device libs way back in 44b6117dfde30d6cc292fabca8ecb0cef4657f7a. Update this to a version derived from the latest. Leaves the float and half cases alone.
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Matt Arsenault
GitHub
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285f2debff
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d2c9ebf369
@ -6,8 +6,12 @@
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//
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//===----------------------------------------------------------------------===//
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#include <clc/float/definitions.h>
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#include <clc/math/clc_ep.h>
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#include <clc/math/clc_fabs.h>
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#include <clc/math/clc_fma.h>
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#include <clc/math/clc_frexp.h>
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#include <clc/math/clc_ldexp.h>
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#include <clc/math/clc_mad.h>
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#include <clc/math/math.h>
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#include <clc/relational/clc_isinf.h>
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@ -176,129 +180,52 @@ __clc_log(float x)
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_CLC_OVERLOAD _CLC_DEF double
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#if defined(COMPILING_LOG2)
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__clc_log2(double x)
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__clc_log2(double a)
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#elif defined(COMPILING_LOG10)
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__clc_log10(double x)
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__clc_log10(double a)
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#else
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__clc_log(double x)
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__clc_log(double a)
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#endif
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{
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int a_exp;
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double m = __clc_frexp(a, &a_exp);
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int b = m < (2.0 / 3.0);
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m = __clc_ldexp(m, b);
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int e = a_exp - b;
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#ifndef COMPILING_LOG2
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// log2_lead and log2_tail sum to an extra-precise version of ln(2)
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const double log2_lead = 6.93147122859954833984e-01; /* 0x3fe62e42e0000000 */
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const double log2_tail = 5.76999904754328540596e-08; /* 0x3e6efa39ef35793c */
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#endif
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double2 x = __clc_ep_div(m - 1.0, __clc_ep_fast_add(1.0, m));
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double s = x.hi * x.hi;
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double p = __clc_mad(s, __clc_mad(s, __clc_mad(s,
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__clc_mad(s, __clc_mad(s, __clc_mad(s, 0x1.3ab76bf559e2bp-3, 0x1.385386b47b09ap-3),
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0x1.7474dd7f4df2ep-3), 0x1.c71c016291751p-3),
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0x1.249249b27acf1p-2), 0x1.99999998ef7b6p-2), 0x1.5555555555780p-1);
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double2 r = __clc_ep_fast_add(__clc_ep_ldexp(x, 1), s * x.hi * p);
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#if defined(COMPILING_LOG10)
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// log10e_lead and log10e_tail sum to an extra-precision version of log10(e)
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// (19 bits in lead)
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const double log10e_lead =
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4.34293746948242187500e-01; /* 0x3fdbcb7800000000 */
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const double log10e_tail =
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7.3495500964015109100644e-7; /* 0x3ea8a93728719535 */
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#elif defined(COMPILING_LOG2)
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// log2e_lead and log2e_tail sum to an extra-precision version of log2(e) (19
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// bits in lead)
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const double log2e_lead = 1.44269180297851562500E+00; /* 0x3FF7154400000000 */
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const double log2e_tail = 3.23791044778235969970E-06; /* 0x3ECB295C17F0BBBE */
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#endif
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// log_thresh1 = 9.39412117004394531250e-1 = 0x3fee0faa00000000
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// log_thresh2 = 1.06449508666992187500 = 0x3ff1082c00000000
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const double log_thresh1 = 0x1.e0faap-1;
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const double log_thresh2 = 0x1.1082cp+0;
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bool is_near = x >= log_thresh1 && x <= log_thresh2;
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// Near 1 code
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double r = x - 1.0;
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double u = r / (2.0 + r);
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double correction = r * u;
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u = u + u;
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double v = u * u;
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double r1 = r;
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const double ca_1 = 8.33333333333317923934e-02; /* 0x3fb55555555554e6 */
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const double ca_2 = 1.25000000037717509602e-02; /* 0x3f89999999bac6d4 */
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const double ca_3 = 2.23213998791944806202e-03; /* 0x3f62492307f1519f */
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const double ca_4 = 4.34887777707614552256e-04; /* 0x3f3c8034c85dfff0 */
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double r2 = __clc_fma(
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u * v, __clc_fma(v, __clc_fma(v, __clc_fma(v, ca_4, ca_3), ca_2), ca_1),
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-correction);
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#if defined(COMPILING_LOG10)
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r = r1;
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r1 = __clc_as_double(__clc_as_ulong(r1) & 0xffffffff00000000);
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r2 = r2 + (r - r1);
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double ret_near = __clc_fma(
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log10e_lead, r1,
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__clc_fma(log10e_lead, r2, __clc_fma(log10e_tail, r1, log10e_tail * r2)));
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#elif defined(COMPILING_LOG2)
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r = r1;
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r1 = __clc_as_double(__clc_as_ulong(r1) & 0xffffffff00000000);
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r2 = r2 + (r - r1);
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double ret_near = __clc_fma(
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log2e_lead, r1,
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__clc_fma(log2e_lead, r2, __clc_fma(log2e_tail, r1, log2e_tail * r2)));
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#if defined COMPILING_LOG2
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r = __clc_ep_add(
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(double)e,
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__clc_ep_mul(
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__clc_ep_make_pair(0x1.71547652b82fep+0, 0x1.777d0ffda0d24p-56), r));
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#elif defined COMPILING_LOG10
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r = __clc_ep_add(
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__clc_ep_mul(
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__clc_ep_make_pair(0x1.34413509f79ffp-2, -0x1.9dc1da994fd21p-59),
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(double)e),
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__clc_ep_mul(
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__clc_ep_make_pair(0x1.bcb7b1526e50ep-2, 0x1.95355baaafad3p-57), r));
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#else
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double ret_near = r1 + r2;
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r = __clc_ep_add(__clc_ep_mul(__clc_ep_make_pair(0x1.62e42fefa39efp-1,
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0x1.abc9e3b39803fp-56),
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(double)e),
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r);
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#endif
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// This is the far from 1 code
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double ret = r.hi;
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// Deal with subnormal
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ulong ux = __clc_as_ulong(x);
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ulong uxs =
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__clc_as_ulong(__clc_as_double(0x03d0000000000000UL | ux) - 0x1.0p-962);
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int c = ux < IMPBIT_DP64;
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ux = c ? uxs : ux;
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int expadjust = c ? 60 : 0;
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ret = __clc_isinf(a) ? a : ret;
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ret = a < 0.0 ? DBL_NAN : ret;
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ret = a == 0.0 ? -INFINITY : ret;
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int xexp = ((__clc_as_int2(ux).hi >> 20) & 0x7ff) - EXPBIAS_DP64 - expadjust;
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double f = __clc_as_double(HALFEXPBITS_DP64 | (ux & MANTBITS_DP64));
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int index = __clc_as_int2(ux).hi >> 13;
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index = ((0x80 | (index & 0x7e)) >> 1) + (index & 0x1);
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double z1 = __CLC_USE_TABLE(ln_tbl_lo, index - 64);
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double q = __CLC_USE_TABLE(ln_tbl_hi, index - 64);
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double f1 = index * 0x1.0p-7;
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double f2 = f - f1;
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u = f2 / __clc_fma(f2, 0.5, f1);
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v = u * u;
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const double cb_1 = 8.33333333333333593622e-02; /* 0x3fb5555555555557 */
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const double cb_2 = 1.24999999978138668903e-02; /* 0x3f89999999865ede */
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const double cb_3 = 2.23219810758559851206e-03; /* 0x3f6249423bd94741 */
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double poly = v * __clc_fma(v, __clc_fma(v, cb_3, cb_2), cb_1);
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double z2 = q + __clc_fma(u, poly, u);
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double dxexp = (double)xexp;
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#if defined(COMPILING_LOG10)
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// Add xexp * log(2) to z1,z2 to get log(x)
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r1 = __clc_fma(dxexp, log2_lead, z1);
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r2 = __clc_fma(dxexp, log2_tail, z2);
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double ret_far = __clc_fma(
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log10e_lead, r1,
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__clc_fma(log10e_lead, r2, __clc_fma(log10e_tail, r1, log10e_tail * r2)));
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#elif defined(COMPILING_LOG2)
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r1 = __clc_fma(log2e_lead, z1, dxexp);
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r2 = __clc_fma(log2e_lead, z2, __clc_fma(log2e_tail, z1, log2e_tail * z2));
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double ret_far = r1 + r2;
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#else
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r1 = __clc_fma(dxexp, log2_lead, z1);
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r2 = __clc_fma(dxexp, log2_tail, z2);
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double ret_far = r1 + r2;
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#endif
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double ret = is_near ? ret_near : ret_far;
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ret = __clc_isinf(x) ? __clc_as_double(PINFBITPATT_DP64) : ret;
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ret = (__clc_isnan(x) | (x < 0.0)) ? __clc_as_double(QNANBITPATT_DP64) : ret;
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ret = x == 0.0 ? __clc_as_double(NINFBITPATT_DP64) : ret;
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return ret;
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}
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