Replace bn_sub_part_words() with bn_sub().

Now that bn_sub() handles word arrays with potentially different lengths,
we no longer need bn_sub_part_words() - call bn_sub() instead. This allows
us to entirely remove the unnecessarily complex bn_sub_part_words() code.

ok tb@

1 files changed, 17 insertions, 155 deletions

diff --git a/lib/libcrypto/bn/bn_mul.c b/lib/libcrypto/bn/bn_mul.c
index 1d56e57b76b..5e270b988f3 100644
--- a/lib/libcrypto/bn/bn_mul.c
+++ b/lib/libcrypto/bn/bn_mul.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_mul.c,v 1.33 2023/02/15 18:10:16 jsing Exp $ */
+/* $OpenBSD: bn_mul.c,v 1.34 2023/02/22 05:57:19 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -269,144 +269,6 @@ bn_mul_add_words(BN_ULONG *r, const BN_ULONG *a, int num, BN_ULONG w)
 }
 #endif
 
-#if defined(OPENSSL_NO_ASM) || !defined(OPENSSL_BN_ASM_PART_WORDS)
-/*
- * Here follows a specialised variant of bn_sub_words(), which has the property
- * performing operations on arrays of different sizes. The sizes of those arrays
- * is expressed through cl, which is the common length (basically,
- * min(len(a),len(b))), and dl, which is the delta between the two lengths,
- * calculated as len(a)-len(b). All lengths are the number of BN_ULONGs. For the
- * operations that require a result array as parameter, it must have the length
- * cl+abs(dl).
- */
-BN_ULONG
-bn_sub_part_words(BN_ULONG *r, const BN_ULONG *a, const BN_ULONG *b, int cl,
-    int dl)
-{
-	BN_ULONG c, t;
-
-	assert(cl >= 0);
-	c = bn_sub_words(r, a, b, cl);
-
-	if (dl == 0)
-		return c;
-
-	r += cl;
-	a += cl;
-	b += cl;
-
-	if (dl < 0) {
-		for (;;) {
-			t = b[0];
-			r[0] = (0 - t - c) & BN_MASK2;
-			if (t != 0)
-				c = 1;
-			if (++dl >= 0)
-				break;
-
-			t = b[1];
-			r[1] = (0 - t - c) & BN_MASK2;
-			if (t != 0)
-				c = 1;
-			if (++dl >= 0)
-				break;
-
-			t = b[2];
-			r[2] = (0 - t - c) & BN_MASK2;
-			if (t != 0)
-				c = 1;
-			if (++dl >= 0)
-				break;
-
-			t = b[3];
-			r[3] = (0 - t - c) & BN_MASK2;
-			if (t != 0)
-				c = 1;
-			if (++dl >= 0)
-				break;
-
-			b += 4;
-			r += 4;
-		}
-	} else {
-		int save_dl = dl;
-		while (c) {
-			t = a[0];
-			r[0] = (t - c) & BN_MASK2;
-			if (t != 0)
-				c = 0;
-			if (--dl <= 0)
-				break;
-
-			t = a[1];
-			r[1] = (t - c) & BN_MASK2;
-			if (t != 0)
-				c = 0;
-			if (--dl <= 0)
-				break;
-
-			t = a[2];
-			r[2] = (t - c) & BN_MASK2;
-			if (t != 0)
-				c = 0;
-			if (--dl <= 0)
-				break;
-
-			t = a[3];
-			r[3] = (t - c) & BN_MASK2;
-			if (t != 0)
-				c = 0;
-			if (--dl <= 0)
-				break;
-
-			save_dl = dl;
-			a += 4;
-			r += 4;
-		}
-		if (dl > 0) {
-			if (save_dl > dl) {
-				switch (save_dl - dl) {
-				case 1:
-					r[1] = a[1];
-					if (--dl <= 0)
-						break;
-				case 2:
-					r[2] = a[2];
-					if (--dl <= 0)
-						break;
-				case 3:
-					r[3] = a[3];
-					if (--dl <= 0)
-						break;
-				}
-				a += 4;
-				r += 4;
-			}
-		}
-		if (dl > 0) {
-			for (;;) {
-				r[0] = a[0];
-				if (--dl <= 0)
-					break;
-				r[1] = a[1];
-				if (--dl <= 0)
-					break;
-				r[2] = a[2];
-				if (--dl <= 0)
-					break;
-				r[3] = a[3];
-				if (--dl <= 0)
-					break;
-
-				a += 4;
-				r += 4;
-			}
-		}
-	}
-	return c;
-}
-#endif
-
 void
 bn_mul_normal(BN_ULONG *r, BN_ULONG *a, int na, BN_ULONG *b, int nb)
 {
@@ -504,15 +366,15 @@ bn_mul_recursive(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b, int n2, int dna,
 	zero = neg = 0;
 	switch (c1 * 3 + c2) {
 	case -4:
-		bn_sub_part_words(t, &(a[n]), a, tna, tna - n); /* - */
-		bn_sub_part_words(&(t[n]), b, &(b[n]), tnb, n - tnb); /* - */
+		bn_sub(t, n, &a[n], tna, a, n);	/* - */
+		bn_sub(&t[n], n, b, n, &b[n], tnb);	/* - */
 		break;
 	case -3:
 		zero = 1;
 		break;
 	case -2:
-		bn_sub_part_words(t, &(a[n]), a, tna, tna - n); /* - */
-		bn_sub_part_words(&(t[n]), &(b[n]), b, tnb, tnb - n); /* + */
+		bn_sub(t, n, &a[n], tna, a, n);	/* - */
+		bn_sub(&t[n], n, &b[n], tnb, b, n);	/* + */
 		neg = 1;
 		break;
 	case -1:
@@ -521,16 +383,16 @@ bn_mul_recursive(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b, int n2, int dna,
 		zero = 1;
 		break;
 	case 2:
-		bn_sub_part_words(t, a, &(a[n]), tna, n - tna); /* + */
-		bn_sub_part_words(&(t[n]), b, &(b[n]), tnb, n - tnb); /* - */
+		bn_sub(t, n, a, n, &a[n], tna);	/* + */
+		bn_sub(&t[n], n, b, n, &b[n], tnb);	/* - */
 		neg = 1;
 		break;
 	case 3:
 		zero = 1;
 		break;
 	case 4:
-		bn_sub_part_words(t, a, &(a[n]), tna, n - tna);
-		bn_sub_part_words(&(t[n]), &(b[n]), b, tnb, tnb - n);
+		bn_sub(t, n, a, n, &a[n], tna);
+		bn_sub(&t[n], n, &b[n], tnb, b, n);
 		break;
 	}
 
@@ -630,14 +492,14 @@ bn_mul_part_recursive(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b, int n, int tna,
 	neg = 0;
 	switch (c1 * 3 + c2) {
 	case -4:
-		bn_sub_part_words(t, &(a[n]), a, tna, tna - n); /* - */
-		bn_sub_part_words(&(t[n]), b, &(b[n]), tnb, n - tnb); /* - */
+		bn_sub(t, n, &a[n], tna, a, n);		/* - */
+		bn_sub(&t[n], n, b, n, &b[n], tnb);	/* - */
 		break;
 	case -3:
 		/* break; */
 	case -2:
-		bn_sub_part_words(t, &(a[n]), a, tna, tna - n); /* - */
-		bn_sub_part_words(&(t[n]), &(b[n]), b, tnb, tnb - n); /* + */
+		bn_sub(t, n, &a[n], tna, a, n);		/* - */
+		bn_sub(&t[n], n, &b[n], tnb, b, n);	/* + */
 		neg = 1;
 		break;
 	case -1:
@@ -645,15 +507,15 @@ bn_mul_part_recursive(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b, int n, int tna,
 	case 1:
 		/* break; */
 	case 2:
-		bn_sub_part_words(t, a, &(a[n]), tna, n - tna); /* + */
-		bn_sub_part_words(&(t[n]), b, &(b[n]), tnb, n - tnb); /* - */
+		bn_sub(t, n, a, n, &a[n], tna);		/* + */
+		bn_sub(&t[n], n, b, n, &b[n], tnb);	/* - */
 		neg = 1;
 		break;
 	case 3:
 		/* break; */
 	case 4:
-		bn_sub_part_words(t, a, &(a[n]), tna, n - tna);
-		bn_sub_part_words(&(t[n]), &(b[n]), b, tnb, tnb - n);
+		bn_sub(t, n, a, n, &a[n], tna);
+		bn_sub(&t[n], n, &b[n], tnb, b, n);
 		break;
 	}
 		/* The zero case isn't yet implemented here. The speedup