From: Lasse Collin <lasse.collin@tukaani.org>
Date: Sun, 3 Aug 2014 18:32:25 +0000 (+0300)
Subject: liblzma: SHA-256: Optimize the Maj macro slightly.
X-Git-Tag: v5.1.4beta~8
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5dcffdbcc23a68abc3ac3539b30be71bc9b5af84;p=thirdparty%2Fxz.git

liblzma: SHA-256: Optimize the Maj macro slightly.

The Maj macro is used where multiple things are added
together, so making Maj a sum of two expressions allows
some extra freedom for the compiler to schedule the
instructions.

I learned this trick from
<http://www.hackersdelight.org/corres.txt>.
---

diff --git a/src/liblzma/check/sha256.c b/src/liblzma/check/sha256.c
index e0e2f10b..5eede5ce 100644
--- a/src/liblzma/check/sha256.c
+++ b/src/liblzma/check/sha256.c
@@ -36,7 +36,7 @@ rotr_32(uint32_t num, unsigned amount)
 		+ s0(W[(i - 15) & 15]))
 
 #define Ch(x, y, z) (z ^ (x & (y ^ z)))
-#define Maj(x, y, z) ((x & y) | (z & (x | y)))
+#define Maj(x, y, z) ((x & (y ^ z)) + (y & z))
 
 #define a(i) T[(0 - i) & 7]
 #define b(i) T[(1 - i) & 7]