Rename bn_umul_hilo() to bn_mulw().

This keeps the naming consistent with the other bignum primitives that have
been recently introduced. Also, use 1/0 intead of h/l (e.g. a1 instead of
ah), as this keeps consistency with other primitives and allows for naming
that works with double word, triple word and quadruple word inputs/outputs.

Discussed with tb@

1 files changed, 59 insertions, 55 deletions

diff --git a/src/lib/libcrypto/bn/bn_internal.h b/src/lib/libcrypto/bn/bn_internal.h
index 64240555d1..2872e21185 100644
--- a/src/lib/libcrypto/bn/bn_internal.h
+++ b/src/lib/libcrypto/bn/bn_internal.h
@@ -1,4 +1,4 @@
-/*      $OpenBSD: bn_internal.h,v 1.6 2023/02/16 10:02:02 jsing Exp $ */
+/*      $OpenBSD: bn_internal.h,v 1.7 2023/02/16 10:41:03 jsing Exp $ */
 /*
  * Copyright (c) 2023 Joel Sing <jsing@openbsd.org>
  *
@@ -159,17 +159,21 @@ bn_subw_subw(BN_ULONG a, BN_ULONG b, BN_ULONG c, BN_ULONG *out_borrow,
 }
 #endif
 
-#ifndef HAVE_BN_UMUL_HILO
+/*
+ * bn_mulw() computes (r1:r0) = a * b, where both inputs are single words,
+ * producing a double word result.
+ */
+#ifndef HAVE_BN_MULW
 #ifdef BN_LLONG
 static inline void
-bn_umul_hilo(BN_ULONG a, BN_ULONG b, BN_ULONG *out_h, BN_ULONG *out_l)
+bn_mulw(BN_ULONG a, BN_ULONG b, BN_ULONG *out_r1, BN_ULONG *out_r0)
 {
         BN_ULLONG r;
 
         r = (BN_ULLONG)a * (BN_ULLONG)b;
 
-        *out_h = r >> BN_BITS2;
-        *out_l = r & BN_MASK2;
+        *out_r1 = r >> BN_BITS2;
+        *out_r0 = r & BN_MASK2;
 }
 
 #else /* !BN_LLONG */
@@ -193,38 +197,38 @@ bn_umul_hilo(BN_ULONG a, BN_ULONG b, BN_ULONG *out_h, BN_ULONG *out_l)
  */
 #if 1
 static inline void
-bn_umul_hilo(BN_ULONG a, BN_ULONG b, BN_ULONG *out_h, BN_ULONG *out_l)
+bn_mulw(BN_ULONG a, BN_ULONG b, BN_ULONG *out_r1, BN_ULONG *out_r0)
 {
-        BN_ULONG ah, al, bh, bl, h, l, x, c1, c2;
+        BN_ULONG a1, a0, b1, b0, r1, r0, c1, c2, x;
 
-        ah = a >> BN_BITS4;
-        al = a & BN_MASK2l;
-        bh = b >> BN_BITS4;
-        bl = b & BN_MASK2l;
+        a1 = a >> BN_BITS4;
+        a0 = a & BN_MASK2l;
+        b1 = b >> BN_BITS4;
+        b0 = b & BN_MASK2l;
 
-        h = ah * bh;
-        l = al * bl;
+        r1 = a1 * b1;
+        r0 = a0 * b0;
 
-        /* (ah * bl) << BN_BITS4, partition the result across h:l with carry. */
-        x = ah * bl;
-        h += x >> BN_BITS4;
+        /* (a1 * b0) << BN_BITS4, partition the result across r1:r0 with carry. */
+        x = a1 * b0;
+        r1 += x >> BN_BITS4;
         x <<= BN_BITS4;
-        c1 = l | x;
-        c2 = l & x;
-        l += x;
-        h += ((c1 & ~l) | c2) >> (BN_BITS2 - 1); /* carry */
-
-        /* (bh * al) << BN_BITS4, partition the result across h:l with carry. */
-        x = bh * al;
-        h += x >> BN_BITS4;
+        c1 = r0 | x;
+        c2 = r0 & x;
+        r0 += x;
+        r1 += ((c1 & ~r0) | c2) >> (BN_BITS2 - 1); /* carry */
+
+        /* (b1 * a0) << BN_BITS4, partition the result across r1:r0 with carry. */
+        x = b1 * a0;
+        r1 += x >> BN_BITS4;
         x <<= BN_BITS4;
-        c1 = l | x;
-        c2 = l & x;
-        l += x;
-        h += ((c1 & ~l) | c2) >> (BN_BITS2 - 1); /* carry */
+        c1 = r0 | x;
+        c2 = r0 & x;
+        r0 += x;
+        r1 += ((c1 & ~r0) | c2) >> (BN_BITS2 - 1); /* carry */
 
-        *out_h = h;
-        *out_l = l;
+        *out_r1 = r1;
+        *out_r0 = r0;
 }
 #else
 
@@ -236,62 +240,62 @@ bn_umul_hilo(BN_ULONG a, BN_ULONG b, BN_ULONG *out_h, BN_ULONG *out_l)
  * implementations should eventually be removed.
  */
 static inline void
-bn_umul_hilo(BN_ULONG a, BN_ULONG b, BN_ULONG *out_h, BN_ULONG *out_l)
+bn_mulw(BN_ULONG a, BN_ULONG b, BN_ULONG *out_r1, BN_ULONG *out_r0)
 {
-        BN_ULONG ah, bh, al, bl, x, h, l;
+        BN_ULONG a1, a0, b1, b0, r1, r0, x;
         BN_ULONG acc0, acc1, acc2, acc3;
 
-        ah = a >> BN_BITS4;
-        bh = b >> BN_BITS4;
-        al = a & BN_MASK2l;
-        bl = b & BN_MASK2l;
+        a1 = a >> BN_BITS4;
+        b1 = b >> BN_BITS4;
+        a0 = a & BN_MASK2l;
+        b0 = b & BN_MASK2l;
 
-        h = ah * bh;
-        l = al * bl;
+        r1 = a1 * b1;
+        r0 = a0 * b0;
 
-        acc0 = l & BN_MASK2l;
-        acc1 = l >> BN_BITS4;
-        acc2 = h & BN_MASK2l;
-        acc3 = h >> BN_BITS4;
+        acc0 = r0 & BN_MASK2l;
+        acc1 = r0 >> BN_BITS4;
+        acc2 = r1 & BN_MASK2l;
+        acc3 = r1 >> BN_BITS4;
 
-        /* (ah * bl) << BN_BITS4, partition the result across h:l. */
-        x = ah * bl;
+        /* (a1 * b0) << BN_BITS4, partition the result across r1:r0. */
+        x = a1 * b0;
         acc1 += x & BN_MASK2l;
         acc2 += (acc1 >> BN_BITS4) + (x >> BN_BITS4);
         acc1 &= BN_MASK2l;
         acc3 += acc2 >> BN_BITS4;
         acc2 &= BN_MASK2l;
 
-        /* (bh * al) << BN_BITS4, partition the result across h:l. */
-        x = bh * al;
+        /* (b1 * a0) << BN_BITS4, partition the result across r1:r0. */
+        x = b1 * a0;
         acc1 += x & BN_MASK2l;
         acc2 += (acc1 >> BN_BITS4) + (x >> BN_BITS4);
         acc1 &= BN_MASK2l;
         acc3 += acc2 >> BN_BITS4;
         acc2 &= BN_MASK2l;
 
-        *out_h = (acc3 << BN_BITS4) | acc2;
-        *out_l = (acc1 << BN_BITS4) | acc0;
+        *out_r1 = (acc3 << BN_BITS4) | acc2;
+        *out_r0 = (acc1 << BN_BITS4) | acc0;
 }
 #endif
 #endif /* !BN_LLONG */
 #endif
 
-#ifndef HAVE_BN_UMUL_LO
+#ifndef HAVE_BN_MULW_LO
 static inline BN_ULONG
-bn_umul_lo(BN_ULONG a, BN_ULONG b)
+bn_mulw_lo(BN_ULONG a, BN_ULONG b)
 {
         return a * b;
 }
 #endif
 
-#ifndef HAVE_BN_UMUL_HI
+#ifndef HAVE_BN_MULW_HI
 static inline BN_ULONG
-bn_umul_hi(BN_ULONG a, BN_ULONG b)
+bn_mulw_hi(BN_ULONG a, BN_ULONG b)
 {
         BN_ULONG h, l;
 
-        bn_umul_hilo(a, b, &h, &l);
+        bn_mulw(a, b, &h, &l);
 
         return h;
 }
@@ -308,7 +312,7 @@ bn_mulw_addw(BN_ULONG a, BN_ULONG b, BN_ULONG c, BN_ULONG *out_r1,
 {
         BN_ULONG carry, r1, r0;
 
-        bn_umul_hilo(a, b, &r1, &r0);
+        bn_mulw(a, b, &r1, &r0);
         bn_addw(r0, c, &carry, &r0);
         r1 += carry;
 
@@ -350,7 +354,7 @@ bn_mulw_addtw(BN_ULONG a, BN_ULONG b, BN_ULONG c2, BN_ULONG c1, BN_ULONG c0,
 {
         BN_ULONG carry, r2, r1, r0, x1, x0;
 
-        bn_umul_hilo(a, b, &x1, &x0);
+        bn_mulw(a, b, &x1, &x0);
         bn_addw(c0, x0, &carry, &r0);
         x1 += carry;
         bn_addw(c1, x1, &carry, &r1);