[XEN] Clean up long division code, fix for C99-mandated

truncation-towards-zero.
Signed-off-by: Keir Fraser <keir@xensource.com>

1 files changed, 291 insertions, 335 deletions

diff --git a/xen/common/lib.c b/xen/common/lib.c
index 661f76420d..c3e77d3cfa 100644
--- a/xen/common/lib.c
+++ b/xen/common/lib.c
@@ -1,41 +1,44 @@
 
 #include <xen/ctype.h>
 #include <xen/lib.h>
+#include <xen/types.h>
 
-
-/* for inc/ctype.h */
+/* for ctype.h */
 unsigned char _ctype[] = {
-_C,_C,_C,_C,_C,_C,_C,_C,                        /* 0-7 */
-_C,_C|_S,_C|_S,_C|_S,_C|_S,_C|_S,_C,_C,         /* 8-15 */
-_C,_C,_C,_C,_C,_C,_C,_C,                        /* 16-23 */
-_C,_C,_C,_C,_C,_C,_C,_C,                        /* 24-31 */
-_S|_SP,_P,_P,_P,_P,_P,_P,_P,                    /* 32-39 */
-_P,_P,_P,_P,_P,_P,_P,_P,                        /* 40-47 */
-_D,_D,_D,_D,_D,_D,_D,_D,                        /* 48-55 */
-_D,_D,_P,_P,_P,_P,_P,_P,                        /* 56-63 */
-_P,_U|_X,_U|_X,_U|_X,_U|_X,_U|_X,_U|_X,_U,      /* 64-71 */
-_U,_U,_U,_U,_U,_U,_U,_U,                        /* 72-79 */
-_U,_U,_U,_U,_U,_U,_U,_U,                        /* 80-87 */
-_U,_U,_U,_P,_P,_P,_P,_P,                        /* 88-95 */
-_P,_L|_X,_L|_X,_L|_X,_L|_X,_L|_X,_L|_X,_L,      /* 96-103 */
-_L,_L,_L,_L,_L,_L,_L,_L,                        /* 104-111 */
-_L,_L,_L,_L,_L,_L,_L,_L,                        /* 112-119 */
-_L,_L,_L,_P,_P,_P,_P,_C,                        /* 120-127 */
-0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,                /* 128-143 */
-0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,                /* 144-159 */
-_S|_SP,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,   /* 160-175 */
-_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,       /* 176-191 */
-_U,_U,_U,_U,_U,_U,_U,_U,_U,_U,_U,_U,_U,_U,_U,_U,       /* 192-207 */
-_U,_U,_U,_U,_U,_U,_U,_P,_U,_U,_U,_U,_U,_U,_U,_L,       /* 208-223 */
-_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,       /* 224-239 */
-_L,_L,_L,_L,_L,_L,_L,_P,_L,_L,_L,_L,_L,_L,_L,_L};      /* 240-255 */
-
-
-/* a couple of 64 bit operations ported from freebsd */
-
-/*-
+    _C,_C,_C,_C,_C,_C,_C,_C,                        /* 0-7 */
+    _C,_C|_S,_C|_S,_C|_S,_C|_S,_C|_S,_C,_C,         /* 8-15 */
+    _C,_C,_C,_C,_C,_C,_C,_C,                        /* 16-23 */
+    _C,_C,_C,_C,_C,_C,_C,_C,                        /* 24-31 */
+    _S|_SP,_P,_P,_P,_P,_P,_P,_P,                    /* 32-39 */
+    _P,_P,_P,_P,_P,_P,_P,_P,                        /* 40-47 */
+    _D,_D,_D,_D,_D,_D,_D,_D,                        /* 48-55 */
+    _D,_D,_P,_P,_P,_P,_P,_P,                        /* 56-63 */
+    _P,_U|_X,_U|_X,_U|_X,_U|_X,_U|_X,_U|_X,_U,      /* 64-71 */
+    _U,_U,_U,_U,_U,_U,_U,_U,                        /* 72-79 */
+    _U,_U,_U,_U,_U,_U,_U,_U,                        /* 80-87 */
+    _U,_U,_U,_P,_P,_P,_P,_P,                        /* 88-95 */
+    _P,_L|_X,_L|_X,_L|_X,_L|_X,_L|_X,_L|_X,_L,      /* 96-103 */
+    _L,_L,_L,_L,_L,_L,_L,_L,                        /* 104-111 */
+    _L,_L,_L,_L,_L,_L,_L,_L,                        /* 112-119 */
+    _L,_L,_L,_P,_P,_P,_P,_C,                        /* 120-127 */
+    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,                /* 128-143 */
+    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,                /* 144-159 */
+    _S|_SP,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,   /* 160-175 */
+    _P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,       /* 176-191 */
+    _U,_U,_U,_U,_U,_U,_U,_U,_U,_U,_U,_U,_U,_U,_U,_U,       /* 192-207 */
+    _U,_U,_U,_U,_U,_U,_U,_P,_U,_U,_U,_U,_U,_U,_U,_L,       /* 208-223 */
+    _L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,       /* 224-239 */
+    _L,_L,_L,_L,_L,_L,_L,_P,_L,_L,_L,_L,_L,_L,_L,_L};      /* 240-255 */
+
+/*
+ * A couple of 64 bit operations ported from FreeBSD.
+ * The code within the '#if BITS_PER_LONG == 32' block below, and no other
+ * code in this file, is distributed under the following licensing terms
+ * This is the modified '3-clause' BSD license with the obnoxious
+ * advertising clause removed, as permitted by University of California.
+ *
  * Copyright (c) 1992, 1993
- *	The Regents of the University of California.  All rights reserved.
+ * The Regents of the University of California.  All rights reserved.
  *
  * This software was developed by the Computer Systems Engineering group
  * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
@@ -49,11 +52,7 @@ _L,_L,_L,_L,_L,_L,_L,_P,_L,_L,_L,_L,_L,_L,_L,_L};      /* 240-255 */
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
- * 3. All advertising materials mentioning features or use of this software
- *    must display the following acknowledgement:
- *	This product includes software developed by the University of
- *	California, Berkeley and its contributors.
- * 4. Neither the name of the University nor the names of its contributors
+ * 3. Neither the name of the University nor the names of its contributors
  *    may be used to endorse or promote products derived from this software
  *    without specific prior written permission.
  *
@@ -68,12 +67,7 @@ _L,_L,_L,_L,_L,_L,_L,_P,_L,_L,_L,_L,_L,_L,_L,_L};      /* 240-255 */
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
- *
- * $FreeBSD: src/sys/libkern/divdi3.c,v 1.6 1999/08/28 00:46:31 peter Exp $
  */
-
-#include <asm/types.h>
-
 #if BITS_PER_LONG == 32
 
 /*
@@ -81,10 +75,10 @@ _L,_L,_L,_L,_L,_L,_L,_P,_L,_L,_L,_L,_L,_L,_L,_L};      /* 240-255 */
  * one or more of the following formats.
  */
 union uu {
-        s64            q;              /* as a (signed) quad */
-        s64            uq;             /* as an unsigned quad */
-        long           sl[2];          /* as two signed longs */
-        unsigned long  ul[2];          /* as two unsigned longs */
+    s64            q;              /* as a (signed) quad */
+    s64            uq;             /* as an unsigned quad */
+    long           sl[2];          /* as two signed longs */
+    unsigned long  ul[2];          /* as two unsigned longs */
 };
 /* XXX RN: Yuck hardcoded endianess :) */
 #define _QUAD_HIGHWORD 1
@@ -122,31 +116,26 @@ union uu {
  * Multiprecision divide.  This algorithm is from Knuth vol. 2 (2nd ed),
  * section 4.3.1, pp. 257--259.
  */
-#define	B	(1 << HALF_BITS)	/* digit base */
+#define B (1 << HALF_BITS) /* digit base */
 
 /* Combine two `digits' to make a single two-digit number. */
-#define	COMBINE(a, b) (((u_long)(a) << HALF_BITS) | (b))
+#define COMBINE(a, b) (((u_long)(a) << HALF_BITS) | (b))
 
-/* select a type for digits in base B: use unsigned short if they fit */
-#if ULONG_MAX == 0xffffffff && USHRT_MAX >= 0xffff
-typedef unsigned short digit;
-#else
+/* select a type for digits in base B */
 typedef u_long digit;
-#endif
 
 /*
  * Shift p[0]..p[len] left `sh' bits, ignoring any bits that
  * `fall out' the left (there never will be any such anyway).
  * We may assume len >= 0.  NOTE THAT THIS WRITES len+1 DIGITS.
  */
-static void
-shl(register digit *p, register int len, register int sh)
+static void shl(register digit *p, register int len, register int sh)
 {
-	register int i;
+    register int i;
 
-	for (i = 0; i < len; i++)
-		p[i] = LHALF(p[i] << sh) | (p[i + 1] >> (HALF_BITS - sh));
-	p[i] = LHALF(p[i] << sh);
+    for (i = 0; i < len; i++)
+        p[i] = LHALF(p[i] << sh) | (p[i + 1] >> (HALF_BITS - sh));
+    p[i] = LHALF(p[i] << sh);
 }
 
 /*
@@ -157,234 +146,222 @@ shl(register digit *p, register int len, register int sh)
  * divisor are 4 `digits' in this base (they are shorter if they have
  * leading zeros).
  */
-u64
-__qdivrem(u64 uq, u64 vq, u64 *arq)
+u64 __qdivrem(u64 uq, u64 vq, u64 *arq)
 {
-	union uu tmp;
-	digit *u, *v, *q;
-	register digit v1, v2;
-	u_long qhat, rhat, t;
-	int m, n, d, j, i;
-	digit uspace[5], vspace[5], qspace[5];
-
-	/*
-	 * Take care of special cases: divide by zero, and u < v.
-	 */
-	if (vq == 0) {
-		/* divide by zero. */
-		static volatile const unsigned int zero = 0;
-
-		tmp.ul[H] = tmp.ul[L] = 1 / zero;
-		if (arq)
-			*arq = uq;
-		return (tmp.q);
-	}
-	if (uq < vq) {
-		if (arq)
-			*arq = uq;
-		return (0);
-	}
-	u = &uspace[0];
-	v = &vspace[0];
-	q = &qspace[0];
-
-	/*
-	 * Break dividend and divisor into digits in base B, then
-	 * count leading zeros to determine m and n.  When done, we
-	 * will have:
-	 *	u = (u[1]u[2]...u[m+n]) sub B
-	 *	v = (v[1]v[2]...v[n]) sub B
-	 *	v[1] != 0
-	 *	1 < n <= 4 (if n = 1, we use a different division algorithm)
-	 *	m >= 0 (otherwise u < v, which we already checked)
-	 *	m + n = 4
-	 * and thus
-	 *	m = 4 - n <= 2
-	 */
-	tmp.uq = uq;
-	u[0] = 0;
-	u[1] = HHALF(tmp.ul[H]);
-	u[2] = LHALF(tmp.ul[H]);
-	u[3] = HHALF(tmp.ul[L]);
-	u[4] = LHALF(tmp.ul[L]);
-	tmp.uq = vq;
-	v[1] = HHALF(tmp.ul[H]);
-	v[2] = LHALF(tmp.ul[H]);
-	v[3] = HHALF(tmp.ul[L]);
-	v[4] = LHALF(tmp.ul[L]);
-	for (n = 4; v[1] == 0; v++) {
-		if (--n == 1) {
-			u_long rbj;	/* r*B+u[j] (not root boy jim) */
-			digit q1, q2, q3, q4;
-
-			/*
-			 * Change of plan, per exercise 16.
-			 *	r = 0;
-			 *	for j = 1..4:
-			 *		q[j] = floor((r*B + u[j]) / v),
-			 *		r = (r*B + u[j]) % v;
-			 * We unroll this completely here.
-			 */
-			t = v[2];	/* nonzero, by definition */
-			q1 = u[1] / t;
-			rbj = COMBINE(u[1] % t, u[2]);
-			q2 = rbj / t;
-			rbj = COMBINE(rbj % t, u[3]);
-			q3 = rbj / t;
-			rbj = COMBINE(rbj % t, u[4]);
-			q4 = rbj / t;
-			if (arq)
-				*arq = rbj % t;
-			tmp.ul[H] = COMBINE(q1, q2);
-			tmp.ul[L] = COMBINE(q3, q4);
-			return (tmp.q);
-		}
-	}
-
-	/*
-	 * By adjusting q once we determine m, we can guarantee that
-	 * there is a complete four-digit quotient at &qspace[1] when
-	 * we finally stop.
-	 */
-	for (m = 4 - n; u[1] == 0; u++)
-		m--;
-	for (i = 4 - m; --i >= 0;)
-		q[i] = 0;
-	q += 4 - m;
-
-	/*
-	 * Here we run Program D, translated from MIX to C and acquiring
-	 * a few minor changes.
-	 *
-	 * D1: choose multiplier 1 << d to ensure v[1] >= B/2.
-	 */
-	d = 0;
-	for (t = v[1]; t < B / 2; t <<= 1)
-		d++;
-	if (d > 0) {
-		shl(&u[0], m + n, d);		/* u <<= d */
-		shl(&v[1], n - 1, d);		/* v <<= d */
-	}
-	/*
-	 * D2: j = 0.
-	 */
-	j = 0;
-	v1 = v[1];	/* for D3 -- note that v[1..n] are constant */
-	v2 = v[2];	/* for D3 */
-	do {
-		register digit uj0, uj1, uj2;
-
-		/*
-		 * D3: Calculate qhat (\^q, in TeX notation).
-		 * Let qhat = min((u[j]*B + u[j+1])/v[1], B-1), and
-		 * let rhat = (u[j]*B + u[j+1]) mod v[1].
-		 * While rhat < B and v[2]*qhat > rhat*B+u[j+2],
-		 * decrement qhat and increase rhat correspondingly.
-		 * Note that if rhat >= B, v[2]*qhat < rhat*B.
-		 */
-		uj0 = u[j + 0];	/* for D3 only -- note that u[j+...] change */
-		uj1 = u[j + 1];	/* for D3 only */
-		uj2 = u[j + 2];	/* for D3 only */
-		if (uj0 == v1) {
-			qhat = B;
-			rhat = uj1;
-			goto qhat_too_big;
-		} else {
-			u_long nn = COMBINE(uj0, uj1);
-			qhat = nn / v1;
-			rhat = nn % v1;
-		}
-		while (v2 * qhat > COMBINE(rhat, uj2)) {
-	qhat_too_big:
-			qhat--;
-			if ((rhat += v1) >= B)
-				break;
-		}
-		/*
-		 * D4: Multiply and subtract.
-		 * The variable `t' holds any borrows across the loop.
-		 * We split this up so that we do not require v[0] = 0,
-		 * and to eliminate a final special case.
-		 */
-		for (t = 0, i = n; i > 0; i--) {
-			t = u[i + j] - v[i] * qhat - t;
-			u[i + j] = LHALF(t);
-			t = (B - HHALF(t)) & (B - 1);
-		}
-		t = u[j] - t;
-		u[j] = LHALF(t);
-		/*
-		 * D5: test remainder.
-		 * There is a borrow if and only if HHALF(t) is nonzero;
-		 * in that (rare) case, qhat was too large (by exactly 1).
-		 * Fix it by adding v[1..n] to u[j..j+n].
-		 */
-		if (HHALF(t)) {
-			qhat--;
-			for (t = 0, i = n; i > 0; i--) { /* D6: add back. */
-				t += u[i + j] + v[i];
-				u[i + j] = LHALF(t);
-				t = HHALF(t);
-			}
-			u[j] = LHALF(u[j] + t);
-		}
-		q[j] = qhat;
-	} while (++j <= m);		/* D7: loop on j. */
-
-	/*
-	 * If caller wants the remainder, we have to calculate it as
-	 * u[m..m+n] >> d (this is at most n digits and thus fits in
-	 * u[m+1..m+n], but we may need more source digits).
-	 */
-	if (arq) {
-		if (d) {
-			for (i = m + n; i > m; --i)
-				u[i] = (u[i] >> d) |
-				    LHALF(u[i - 1] << (HALF_BITS - d));
-			u[i] = 0;
-		}
-		tmp.ul[H] = COMBINE(uspace[1], uspace[2]);
-		tmp.ul[L] = COMBINE(uspace[3], uspace[4]);
-		*arq = tmp.q;
-	}
-
-	tmp.ul[H] = COMBINE(qspace[1], qspace[2]);
-	tmp.ul[L] = COMBINE(qspace[3], qspace[4]);
-	return (tmp.q);
+    union uu tmp;
+    digit *u, *v, *q;
+    register digit v1, v2;
+    u_long qhat, rhat, t;
+    int m, n, d, j, i;
+    digit uspace[5], vspace[5], qspace[5];
+
+    /*
+     * Take care of special cases: divide by zero, and u < v.
+     */
+    if (vq == 0) {
+        /* divide by zero. */
+        static volatile const unsigned int zero = 0;
+
+        tmp.ul[H] = tmp.ul[L] = 1 / zero;
+        if (arq)
+            *arq = uq;
+        return (tmp.q);
+    }
+    if (uq < vq) {
+        if (arq)
+            *arq = uq;
+        return (0);
+    }
+    u = &uspace[0];
+    v = &vspace[0];
+    q = &qspace[0];
+
+    /*
+     * Break dividend and divisor into digits in base B, then
+     * count leading zeros to determine m and n.  When done, we
+     * will have:
+     * u = (u[1]u[2]...u[m+n]) sub B
+     * v = (v[1]v[2]...v[n]) sub B
+     * v[1] != 0
+     * 1 < n <= 4 (if n = 1, we use a different division algorithm)
+     * m >= 0 (otherwise u < v, which we already checked)
+     * m + n = 4
+     * and thus
+     * m = 4 - n <= 2
+     */
+    tmp.uq = uq;
+    u[0] = 0;
+    u[1] = HHALF(tmp.ul[H]);
+    u[2] = LHALF(tmp.ul[H]);
+    u[3] = HHALF(tmp.ul[L]);
+    u[4] = LHALF(tmp.ul[L]);
+    tmp.uq = vq;
+    v[1] = HHALF(tmp.ul[H]);
+    v[2] = LHALF(tmp.ul[H]);
+    v[3] = HHALF(tmp.ul[L]);
+    v[4] = LHALF(tmp.ul[L]);
+    for (n = 4; v[1] == 0; v++) {
+        if (--n == 1) {
+            u_long rbj; /* r*B+u[j] (not root boy jim) */
+            digit q1, q2, q3, q4;
+
+            /*
+             * Change of plan, per exercise 16.
+             * r = 0;
+             * for j = 1..4:
+             *  q[j] = floor((r*B + u[j]) / v),
+             *  r = (r*B + u[j]) % v;
+             * We unroll this completely here.
+             */
+            t = v[2]; /* nonzero, by definition */
+            q1 = u[1] / t;
+            rbj = COMBINE(u[1] % t, u[2]);
+            q2 = rbj / t;
+            rbj = COMBINE(rbj % t, u[3]);
+            q3 = rbj / t;
+            rbj = COMBINE(rbj % t, u[4]);
+            q4 = rbj / t;
+            if (arq)
+                *arq = rbj % t;
+            tmp.ul[H] = COMBINE(q1, q2);
+            tmp.ul[L] = COMBINE(q3, q4);
+            return (tmp.q);
+        }
+    }
+
+    /*
+     * By adjusting q once we determine m, we can guarantee that
+     * there is a complete four-digit quotient at &qspace[1] when
+     * we finally stop.
+     */
+    for (m = 4 - n; u[1] == 0; u++)
+        m--;
+    for (i = 4 - m; --i >= 0;)
+        q[i] = 0;
+    q += 4 - m;
+
+    /*
+     * Here we run Program D, translated from MIX to C and acquiring
+     * a few minor changes.
+     *
+     * D1: choose multiplier 1 << d to ensure v[1] >= B/2.
+     */
+    d = 0;
+    for (t = v[1]; t < B / 2; t <<= 1)
+        d++;
+    if (d > 0) {
+        shl(&u[0], m + n, d);  /* u <<= d */
+        shl(&v[1], n - 1, d);  /* v <<= d */
+    }
+    /*
+     * D2: j = 0.
+     */
+    j = 0;
+    v1 = v[1]; /* for D3 -- note that v[1..n] are constant */
+    v2 = v[2]; /* for D3 */
+    do {
+        register digit uj0, uj1, uj2;
+
+        /*
+         * D3: Calculate qhat (\^q, in TeX notation).
+         * Let qhat = min((u[j]*B + u[j+1])/v[1], B-1), and
+         * let rhat = (u[j]*B + u[j+1]) mod v[1].
+         * While rhat < B and v[2]*qhat > rhat*B+u[j+2],
+         * decrement qhat and increase rhat correspondingly.
+         * Note that if rhat >= B, v[2]*qhat < rhat*B.
+         */
+        uj0 = u[j + 0]; /* for D3 only -- note that u[j+...] change */
+        uj1 = u[j + 1]; /* for D3 only */
+        uj2 = u[j + 2]; /* for D3 only */
+        if (uj0 == v1) {
+            qhat = B;
+            rhat = uj1;
+            goto qhat_too_big;
+        } else {
+            u_long nn = COMBINE(uj0, uj1);
+            qhat = nn / v1;
+            rhat = nn % v1;
+        }
+        while (v2 * qhat > COMBINE(rhat, uj2)) {
+        qhat_too_big:
+            qhat--;
+            if ((rhat += v1) >= B)
+                break;
+        }
+        /*
+         * D4: Multiply and subtract.
+         * The variable `t' holds any borrows across the loop.
+         * We split this up so that we do not require v[0] = 0,
+         * and to eliminate a final special case.
+         */
+        for (t = 0, i = n; i > 0; i--) {
+            t = u[i + j] - v[i] * qhat - t;
+            u[i + j] = LHALF(t);
+            t = (B - HHALF(t)) & (B - 1);
+        }
+        t = u[j] - t;
+        u[j] = LHALF(t);
+        /*
+         * D5: test remainder.
+         * There is a borrow if and only if HHALF(t) is nonzero;
+         * in that (rare) case, qhat was too large (by exactly 1).
+         * Fix it by adding v[1..n] to u[j..j+n].
+         */
+        if (HHALF(t)) {
+            qhat--;
+            for (t = 0, i = n; i > 0; i--) { /* D6: add back. */
+                t += u[i + j] + v[i];
+                u[i + j] = LHALF(t);
+                t = HHALF(t);
+            }
+            u[j] = LHALF(u[j] + t);
+        }
+        q[j] = qhat;
+    } while (++j <= m);  /* D7: loop on j. */
+
+    /*
+     * If caller wants the remainder, we have to calculate it as
+     * u[m..m+n] >> d (this is at most n digits and thus fits in
+     * u[m+1..m+n], but we may need more source digits).
+     */
+    if (arq) {
+        if (d) {
+            for (i = m + n; i > m; --i)
+                u[i] = (u[i] >> d) |
+                    LHALF(u[i - 1] << (HALF_BITS - d));
+            u[i] = 0;
+        }
+        tmp.ul[H] = COMBINE(uspace[1], uspace[2]);
+        tmp.ul[L] = COMBINE(uspace[3], uspace[4]);
+        *arq = tmp.q;
+    }
+
+    tmp.ul[H] = COMBINE(qspace[1], qspace[2]);
+    tmp.ul[L] = COMBINE(qspace[3], qspace[4]);
+    return (tmp.q);
 }
 
 /*
  * Divide two signed quads.
- * ??? if -1/2 should produce -1 on this machine, this code is wrong
- * (Grzegorz Milos) Note for the above: -1/2 is 0. And so it should.
+ * Truncates towards zero, as required by C99.
  */
-s64
-__divdi3(s64 a, s64 b)
+s64 __divdi3(s64 a, s64 b)
 {
-	u64 ua, ub, uq;
-	int neg;
-
-	if (a < 0)
-		ua = -(u64)a, neg = 1;
-	else
-		ua = a, neg = 0;
-	if (b < 0)
-		ub = -(u64)b, neg ^= 1;
-	else
-		ub = b;
-	uq = __qdivrem(ua, ub, (u64 *)0);
-	return (neg ? -uq : uq);
+    u64 ua, ub, uq;
+    int neg = (a < 0) ^ (b < 0);
+    ua = (a < 0) ? -(u64)a : a;
+    ub = (b < 0) ? -(u64)b : b;
+    uq = __qdivrem(ua, ub, (u64 *)0);
+    return (neg ? -uq : uq);
 }
 
 
 /*
  * Divide two unsigned quads.
  */
-u64
-__udivdi3(u64 a, u64 b)
+u64 __udivdi3(u64 a, u64 b)
 {
-
-        return (__qdivrem(a, b, (u64 *)0));
+    return __qdivrem(a, b, (u64 *)0);
 }
 
 /*
@@ -392,87 +369,66 @@ __udivdi3(u64 a, u64 b)
  */
 u64 __umoddi3(u64 a, u64 b)
 {
-	u64 rem;
-	__qdivrem(a, b, &rem);
-	return rem;
+    u64 rem;
+    __qdivrem(a, b, &rem);
+    return rem;
 }
 
 /*
  * Remainder of signed quad division.
- * The result of mod is not always equal to division
- * remainder. The following example shows the result for all
- * four possible cases:
+ * Truncates towards zero, as required by C99:
  *  11 %  5 =  1
- * -11 %  5 =  4
- *  11 % -5 = -4
- * -11 % -5 = -1
+ * -11 %  5 = -1
+ *  11 % -5 =  1
+ * -11 % -5 =  1
  */
 s64 __moddi3(s64 a, s64 b)
 {
-	u64 ua, ub, urem;
-	int neg1, neg2;
-
-	if (a < 0)
-		ua = -(u64)a, neg1 = 1;
-	else
-		ua = a, neg1 = 0;
-        
-	if (b < 0)
-		ub = -(u64)b, neg2 = 1;
-	else
-		ub = b, neg2 = 0;
-	__qdivrem(ua, ub, &urem);
-    
-	/* There 4 different cases: */
-	if (neg1) {
-		if (neg2)
-			return -urem;
-		else
-			return ub - urem;
-	} else {
-		if (neg2)
-			return -ub + urem;
-		else
-			return urem;
-	}
+    u64 ua, ub, urem;
+    int neg = (a < 0);
+    ua = neg ? -(u64)a : a;
+    ub = (b < 0) ? -(u64)b : b;
+    __qdivrem(ua, ub, &urem);
+    return (neg ? -urem : urem);
 }
 
 #endif /* BITS_PER_LONG == 32 */
 
 unsigned long long parse_size_and_unit(const char *s, const char **ps)
 {
-	unsigned long long ret;
-	const char *s1;
-
-	ret = simple_strtoull(s, &s1, 0);
-
-	switch (*s1) {
-	case 'G': case 'g':
-		ret <<= 10;
-	case 'M': case 'm':
-		ret <<= 10;
-	case 'K': case 'k':
-		ret <<= 10;
-	case 'B': case 'b':
-		s1++;
-		break;
-	default:
-		ret <<= 10; /* default to kB */
-		break;
-	}
-
-	if (ps != NULL)
-		*ps = s1;
-
-	return ret;
+    unsigned long long ret;
+    const char *s1;
+
+    ret = simple_strtoull(s, &s1, 0);
+
+    switch ( *s1 )
+    {
+    case 'G': case 'g':
+        ret <<= 10;
+    case 'M': case 'm':
+        ret <<= 10;
+    case 'K': case 'k':
+        ret <<= 10;
+    case 'B': case 'b':
+        s1++;
+        break;
+    default:
+        ret <<= 10; /* default to kB */
+        break;
+    }
+
+    if ( ps != NULL )
+        *ps = s1;
+
+    return ret;
 }
 
 /*
  * Local variables:
  * mode: C
  * c-set-style: "BSD"
- * c-basic-offset: 8
- * tab-width: 8
- * indent-tabs-mode: t
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
  * End:
  */