From: Andy Polyakov <appro@openssl.org>
Date: Wed, 20 Aug 2014 22:13:55 +0000 (+0200)
Subject: sha1-mb-x86_64.pl: add commentary.
X-Git-Tag: OpenSSL_1_0_2-beta3~102
X-Git-Url: https://git.openssl.org/?p=openssl.git;a=commitdiff_plain;h=a89adc148ec1ba86da9528a759030095a4010d08

sha1-mb-x86_64.pl: add commentary.

Reviewed-by: Emilia Kasper <emilia@openssl.org>
(cherry picked from commit e608273a8094a95a5703c26a428a007497e74392)
---

diff --git a/crypto/sha/asm/sha1-mb-x86_64.pl b/crypto/sha/asm/sha1-mb-x86_64.pl
index e9bc8e5c47..a8ee075eaa 100644
--- a/crypto/sha/asm/sha1-mb-x86_64.pl
+++ b/crypto/sha/asm/sha1-mb-x86_64.pl
@@ -107,6 +107,19 @@ my ($i,$a,$b,$c,$d,$e)=@_;
 my $j=$i+1;
 my $k=$i+2;
 
+# Loads are performed 2+3/4 iterations in advance. 3/4 means that out
+# of 4 words you would expect to be loaded per given iteration one is
+# spilled to next iteration. In other words indices in four input
+# streams are distributed as following:
+#
+# $i==0:	0,0,0,0,1,1,1,1,2,2,2,
+# $i==1:	2,3,3,3,
+# $i==2:	3,4,4,4,
+# ...
+# $i==13:	14,15,15,15,
+# $i==14:	15
+# 
+# Then at $i==15 Xupdate is applied one iteration in advance...
 $code.=<<___ if ($i==0);
 	movd		(@ptr[0]),@Xi[0]
 	 lea		`16*4`(@ptr[0]),@ptr[0]