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Reduce diff between msun/src/e_pow.c and msun/src/e_powf.c.

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Remove unnecessary casts, use integer literal constants instead of
floating point constants where possible, and introduce three const
static variables to hold 0.5, 0.25, and 1/3.

PR:		229420
Submitted by:	Steve Kargl <sgk@troutmask.apl.washington.edu>
MFC after:	1 week
This commit is contained in:
Mark Johnston 2018-07-08 16:33:58 +00:00
parent 46a846f791
commit 7525d42f70
2 changed files with 14 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
lib/msun/src/e_pow.c
View File

@ -65,6 +65,9 @@ bp[] = {1.0, 1.5,},
dp_h[] = { 0.0, 5.84962487220764160156e-01,}, /* 0x3FE2B803, 0x40000000 */
dp_l[] = { 0.0, 1.35003920212974897128e-08,}, /* 0x3E4CFDEB, 0x43CFD006 */
zero = 0.0,
half = 0.5,
qrtr = 0.25,
thrd = 3.3333333333333331e-01, /* 0x3fd55555, 0x55555555 */
one = 1.0,
two = 2.0,
two53 = 9007199254740992.0, /* 0x43400000, 0x00000000 */
@ -197,7 +200,7 @@ __ieee754_pow(double x, double y)
/* now |1-x| is tiny <= 2**-20, suffice to compute
log(x) by x-x^2/2+x^3/3-x^4/4 */
t = ax-one; /* t has 20 trailing zeros */
w = (t*t)*(0.5-t*(0.3333333333333333333333-t*0.25));
w = (t*t)*(half-t*(thrd-t*qrtr));
u = ivln2_h*t; /* ivln2_h has 21 sig. bits */
v = t*ivln2_l-w*ivln2;
t1 = u+v;
@ -234,9 +237,9 @@ __ieee754_pow(double x, double y)
r = s2*s2*(L1+s2*(L2+s2*(L3+s2*(L4+s2*(L5+s2*L6)))));
r += s_l*(s_h+ss);
s2 = s_h*s_h;
t_h = 3.0+s2+r;
t_h = 3+s2+r;
SET_LOW_WORD(t_h,0);
t_l = r-((t_h-3.0)-s2);
t_l = r-((t_h-3)-s2);
/* u+v = ss*(1+...) */
u = s_h*t_h;
v = s_l*t_h+t_l*ss;
@ -247,7 +250,7 @@ __ieee754_pow(double x, double y)
z_h = cp_h*p_h; /* cp_h+cp_l = 2/(3*log2) */
z_l = cp_l*p_h+p_l*cp+dp_l[k];
/* log2(ax) = (ss+..)*2/(3*log2) = n + dp_h + z_h + z_l */
t = (double)n;
t = n;
t1 = (((z_h+z_l)+dp_h[k])+t);
SET_LOW_WORD(t1,0);
t2 = z_l-(((t1-t)-dp_h[k])-z_h);

11
lib/msun/src/e_powf.c
View File

@ -24,6 +24,9 @@ bp[] = {1.0, 1.5,},
dp_h[] = { 0.0, 5.84960938e-01,}, /* 0x3f15c000 */
dp_l[] = { 0.0, 1.56322085e-06,}, /* 0x35d1cfdc */
zero = 0.0,
half = 0.5,
qrtr = 0.25,
thrd = 3.33333343e-01, /* 0x3eaaaaab */
one = 1.0,
two = 2.0,
two24 = 16777216.0, /* 0x4b800000 */
@ -138,7 +141,7 @@ __ieee754_powf(float x, float y)
/* now |1-x| is tiny <= 2**-20, suffice to compute
log(x) by x-x^2/2+x^3/3-x^4/4 */
t = ax-1; /* t has 20 trailing zeros */
w = (t*t)*((float)0.5-t*((float)0.333333333333-t*(float)0.25));
w = (t*t)*(half-t*(thrd-t*qrtr));
u = ivln2_h*t; /* ivln2_h has 16 sig. bits */
v = t*ivln2_l-w*ivln2;
t1 = u+v;
@ -177,10 +180,10 @@ __ieee754_powf(float x, float y)
r = s2*s2*(L1+s2*(L2+s2*(L3+s2*(L4+s2*(L5+s2*L6)))));
r += s_l*(s_h+s);
s2 = s_h*s_h;
t_h = (float)3.0+s2+r;
t_h = 3+s2+r;
GET_FLOAT_WORD(is,t_h);
SET_FLOAT_WORD(t_h,is&0xfffff000);
t_l = r-((t_h-(float)3.0)-s2);
t_l = r-((t_h-3)-s2);
/* u+v = s*(1+...) */
u = s_h*t_h;
v = s_l*t_h+t_l*s;
@ -192,7 +195,7 @@ __ieee754_powf(float x, float y)
z_h = cp_h*p_h; /* cp_h+cp_l = 2/(3*log2) */
z_l = cp_l*p_h+p_l*cp+dp_l[k];
/* log2(ax) = (s+..)*2/(3*log2) = n + dp_h + z_h + z_l */
t = (float)n;
t = n;
t1 = (((z_h+z_l)+dp_h[k])+t);
GET_FLOAT_WORD(is,t1);
SET_FLOAT_WORD(t1,is&0xfffff000);