Minor MIPS III/IV tune-up.

[openssl.git] / crypto / bn / bn_div.c

diff --git a/crypto/bn/bn_div.c b/crypto/bn/bn_div.c
index baff07040a3e9fd88c891786b71bb4cf8a7f27fe..6dd5d99ec4a8fac27d17b0db329d315c5d4ad86f 100644 (file)
--- a/crypto/bn/bn_div.c
+++ b/crypto/bn/bn_div.c
@@ -200,57 +200,99 @@ int BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor,
 
        for (i=0; i<loop-1; i++)
                {
-               BN_ULONG q,n0,n1;
-               BN_ULONG l0;
+               BN_ULONG q,l0;
+#ifdef BN_DIV3W
+               q=bn_div_3_words(wnump,d1,d0);
+#else
+
+#if !defined(NO_ASM) && !defined(PEDANTIC)
+# if defined(__GNUC__) && __GNUC__>=2
+#  if defined(__i386)
+   /*
+    * There were two reasons for implementing this template:
+    * - GNU C generates a call to a function (__udivdi3 to be exact)
+    *   in reply to ((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0 (I fail to
+    *   understand why...);
+    * - divl doesn't only calculate quotient, but also leaves
+    *   remainder in %edx which we can definitely use here:-)
+    *
+    *                                  <appro@fy.chalmers.se>
+    */
+#  define bn_div_words(n0,n1,d0)               \
+       ({  asm volatile (                      \
+               "divl   %4"                     \
+               : "=a"(q), "=d"(rem)            \
+               : "a"(n1), "d"(n0), "g"(d0)     \
+               : "cc");                        \
+           q;                                  \
+       })
+#  define REMINDER_IS_ALREADY_CALCULATED
+#  endif /* __<cpu> */
+# endif /* __GNUC__ */
+#endif /* NO_ASM */
+               BN_ULONG n0,n1,rem=0;
 
-               wnum.d--; wnum.top++;
                n0=wnump[0];
                n1=wnump[-1];
                if (n0 == d0)
                        q=BN_MASK2;
                else
+#if defined(BN_LLONG) && defined(BN_DIV2W) && !defined(bn_div_words)
+                       q=((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0;
+#else
                        q=bn_div_words(n0,n1,d0);
+#endif
                {
 #ifdef BN_LLONG
-               BN_ULLONG t1,t2,rem;
-               t1=((BN_ULLONG)n0<<BN_BITS2)|n1;
+               BN_ULLONG t2;
+
+#ifndef REMINDER_IS_ALREADY_CALCULATED
+               /*
+                * rem doesn't have to be BN_ULLONG. The least we
+                * know it's less that d0, isn't it?
+                */
+               rem=(n1-q*d0)&BN_MASK2;
+#endif
+               t2=(BN_ULLONG)d1*q;
+
                for (;;)
                        {
-                       t2=(BN_ULLONG)d1*q;
-                       rem=t1-(BN_ULLONG)q*d0;
-                       if ((rem>>BN_BITS2) ||
-                               (t2 <= ((BN_ULLONG)(rem<<BN_BITS2)+wnump[-2])))
+                        if (t2 <= ((((BN_ULLONG)rem)<<BN_BITS2)|wnump[-2]))
                                break;
                        q--;
+                       rem += d0;
+                       if (rem < d0) break; /* don't let rem overflow */
+                       t2 -= d1;
                        }
 #else
-               BN_ULONG t1l,t1h,t2l,t2h,t3l,t3h,ql,qh,t3t;
-               t1h=n0;
-               t1l=n1;
+               BN_ULONG t2l,t2h,ql,qh;
+
+#ifndef REMINDER_IS_ALREADY_CALCULATED
+               /*
+                * It's more than enough with the only multiplication.
+                * See the comment above in BN_LLONG section...
+                */
+               rem=(n1-q*d0)&BN_MASK2;
+#endif
+               t2l=LBITS(d1); t2h=HBITS(d1);
+               ql =LBITS(q);  qh =HBITS(q);
+               mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1*q; */
+
                for (;;)
                        {
-                       t2l=LBITS(d1); t2h=HBITS(d1);
-                       ql =LBITS(q);  qh =HBITS(q);
-                       mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1*q; */
-
-                       t3t=LBITS(d0); t3h=HBITS(d0);
-                       mul64(t3t,t3h,ql,qh); /* t3=t1-(BN_ULLONG)q*d0; */
-                       t3l=(t1l-t3t)&BN_MASK2;
-                       if (t3l > t1l) t3h++;
-                       t3h=(t1h-t3h)&BN_MASK2;
-
-                       /*if ((t3>>BN_BITS2) ||
-                               (t2 <= ((t3<<BN_BITS2)+wnump[-2])))
-                               break; */
-                       if (t3h) break;
-                       if (t2h < t3l) break;
-                       if ((t2h == t3l) && (t2l <= wnump[-2])) break;
-
+                       if ((t2h < rem) ||
+                               ((t2h == rem) && (t2l <= wnump[-2])))
+                               break;
                        q--;
+                       rem += d0;
+                       if (rem < d0) break; /* don't let rem overflow */
+                       if (t2l < d1) t2h--; t2l -= d1;
                        }
 #endif
                }
+#endif /* !BN_DIV3W */
                l0=bn_mul_words(tmp->d,sdiv->d,div_n,q);
+               wnum.d--; wnum.top++;
                tmp->d[div_n]=l0;
                for (j=div_n+1; j>0; j--)
                        if (tmp->d[j-1]) break;