From 0b44a0315b47dd8eced9f3b7f31580cf14bbfc01 Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Sat, 12 Feb 2011 00:22:29 -0500
Subject: initial check-in, version 0.5.0

---
 src/math/s_remquof.c | 118 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 118 insertions(+)
 create mode 100644 src/math/s_remquof.c

(limited to 'src/math/s_remquof.c')

diff --git a/src/math/s_remquof.c b/src/math/s_remquof.c
new file mode 100644
index 00000000..be2a561a
--- /dev/null
+++ b/src/math/s_remquof.c
@@ -0,0 +1,118 @@
+/* @(#)e_fmod.c 1.3 95/01/18 */
+/*-
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunSoft, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice 
+ * is preserved.
+ * ====================================================
+ */
+
+#include <math.h>
+#include "math_private.h"
+
+static const float Zero[] = {0.0, -0.0,};
+
+/*
+ * Return the IEEE remainder and set *quo to the last n bits of the
+ * quotient, rounded to the nearest integer.  We choose n=31 because
+ * we wind up computing all the integer bits of the quotient anyway as
+ * a side-effect of computing the remainder by the shift and subtract
+ * method.  In practice, this is far more bits than are needed to use
+ * remquo in reduction algorithms.
+ */
+float
+remquof(float x, float y, int *quo)
+{
+        int32_t n,hx,hy,hz,ix,iy,sx,i;
+        uint32_t q,sxy;
+
+        GET_FLOAT_WORD(hx,x);
+        GET_FLOAT_WORD(hy,y);
+        sxy = (hx ^ hy) & 0x80000000;
+        sx = hx&0x80000000;             /* sign of x */
+        hx ^=sx;                /* |x| */
+        hy &= 0x7fffffff;       /* |y| */
+
+    /* purge off exception values */
+        if(hy==0||hx>=0x7f800000||hy>0x7f800000) /* y=0,NaN;or x not finite */
+            return (x*y)/(x*y);
+        if(hx<hy) {
+            q = 0;
+            goto fixup; /* |x|<|y| return x or x-y */
+        } else if(hx==hy) {
+            *quo = 1;
+            return Zero[(uint32_t)sx>>31];     /* |x|=|y| return x*0*/
+        }
+
+    /* determine ix = ilogb(x) */
+        if(hx<0x00800000) {     /* subnormal x */
+            for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1;
+        } else ix = (hx>>23)-127;
+
+    /* determine iy = ilogb(y) */
+        if(hy<0x00800000) {     /* subnormal y */
+            for (iy = -126,i=(hy<<8); i>0; i<<=1) iy -=1;
+        } else iy = (hy>>23)-127;
+
+    /* set up {hx,lx}, {hy,ly} and align y to x */
+        if(ix >= -126)
+            hx = 0x00800000|(0x007fffff&hx);
+        else {          /* subnormal x, shift x to normal */
+            n = -126-ix;
+            hx <<= n;
+        }
+        if(iy >= -126)
+            hy = 0x00800000|(0x007fffff&hy);
+        else {          /* subnormal y, shift y to normal */
+            n = -126-iy;
+            hy <<= n;
+        }
+
+    /* fix point fmod */
+        n = ix - iy;
+        q = 0;
+        while(n--) {
+            hz=hx-hy;
+            if(hz<0) hx = hx << 1;
+            else {hx = hz << 1; q++;}
+            q <<= 1;
+        }
+        hz=hx-hy;
+        if(hz>=0) {hx=hz;q++;}
+
+    /* convert back to floating value and restore the sign */
+        if(hx==0) {                             /* return sign(x)*0 */
+            *quo = (sxy ? -q : q);
+            return Zero[(uint32_t)sx>>31];
+        }
+        while(hx<0x00800000) {          /* normalize x */
+            hx <<= 1;
+            iy -= 1;
+        }
+        if(iy>= -126) {         /* normalize output */
+            hx = ((hx-0x00800000)|((iy+127)<<23));
+        } else {                /* subnormal output */
+            n = -126 - iy;
+            hx >>= n;
+        }
+fixup:
+        SET_FLOAT_WORD(x,hx);
+        y = fabsf(y);
+        if (y < 0x1p-125f) {
+            if (x+x>y || (x+x==y && (q & 1))) {
+                q++;
+                x-=y;
+            }
+        } else if (x>0.5f*y || (x==0.5f*y && (q & 1))) {
+            q++;
+            x-=y;
+        }
+        GET_FLOAT_WORD(hx,x);
+        SET_FLOAT_WORD(x,hx^sx);
+        q &= 0x7fffffff;
+        *quo = (sxy ? -q : q);
+        return x;
+}
-- 
cgit 1.4.1