Enable s2n-bignum word_clz() on amd64.

The BN_num_bits_word() function is a hot path, being called more than
80 million times during a libcrypto regress run. The word_clz()
implementation uses five instructions to do the same as the generic code
that uses more than 60 instructions.

Discussed with tb@

1 files changed, 2 insertions, 1 deletions

diff --git a/src/lib/libcrypto/arch/amd64/Makefile.inc b/src/lib/libcrypto/arch/amd64/Makefile.inc
index 5e433b572d..e9c7732691 100644
--- a/src/lib/libcrypto/arch/amd64/Makefile.inc
+++ b/src/lib/libcrypto/arch/amd64/Makefile.inc
@@ -1,4 +1,4 @@
-# $OpenBSD: Makefile.inc,v 1.11 2023/01/29 14:00:41 jsing Exp $
+# $OpenBSD: Makefile.inc,v 1.12 2023/02/16 11:13:05 jsing Exp $
 
 # amd64-specific libcrypto build rules
 
@@ -39,6 +39,7 @@ SRCS += bignum_sqr.S
 SRCS += bignum_sqr_4_8_alt.S
 SRCS += bignum_sqr_8_16_alt.S
 SRCS += bignum_sub.S
+SRCS += word_clz.S
 
 # camellia
 SRCS+=  cmll_misc.c