Fix unused variables in bn/generic.c

bl and bh are never used by macros if either BN_UMULT_LOHI or
BN_UMULT_HIGH are defined.

Change-Id: I7fdd45014a6b78cc586b5223396e09bc213608a5
Reviewed-on: https://boringssl-review.googlesource.com/2105
Reviewed-by: Adam Langley <agl@google.com>

crypto/bn/generic.c

@@ -822,9 +822,9 @@ BN_ULONG bn_sub_words(BN_ULONG *r, const BN_ULONG *a, const BN_ULONG *b,
 #endif /* !BN_LLONG */
 
 void bn_mul_comba8(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b) {
-#ifdef BN_LLONG
+#if defined(BN_LLONG)
   BN_ULLONG t;
-#else
+#elif !defined(BN_UMULT_LOHI) && !defined(BN_UMULT_HIGH)
   BN_ULONG bl, bh;
 #endif
   BN_ULONG t1, t2;
@@ -930,9 +930,9 @@ void bn_mul_comba8(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b) {
 }
 
 void bn_mul_comba4(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b) {
-#ifdef BN_LLONG
+#if defined(BN_LLONG)
   BN_ULLONG t;
-#else
+#elif !defined(BN_UMULT_LOHI) && !defined(BN_UMULT_HIGH)
   BN_ULONG bl, bh;
 #endif
   BN_ULONG t1, t2;
@@ -974,9 +974,9 @@ void bn_mul_comba4(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b) {
 }
 
 void bn_sqr_comba8(BN_ULONG *r, const BN_ULONG *a) {
-#ifdef BN_LLONG
+#if defined(BN_LLONG)
   BN_ULLONG t, tt;
-#else
+#elif !defined(BN_UMULT_LOHI) && !defined(BN_UMULT_HIGH)
   BN_ULONG bl, bh;
 #endif
   BN_ULONG t1, t2;
@@ -1054,9 +1054,9 @@ void bn_sqr_comba8(BN_ULONG *r, const BN_ULONG *a) {
 }
 
 void bn_sqr_comba4(BN_ULONG *r, const BN_ULONG *a) {
-#ifdef BN_LLONG
+#if defined(BN_LLONG)
   BN_ULLONG t, tt;
-#else
+#elif !defined(BN_UMULT_LOHI) && !defined(BN_UMULT_HIGH)
   BN_ULONG bl, bh;
 #endif
   BN_ULONG t1, t2;