From: Andy Polyakov <appro@openssl.org>
Date: Mon, 21 Dec 2015 13:26:12 +0000 (+0100)
Subject: bn/asm/bn-c64xplus.asm: update commentary.
X-Git-Tag: OpenSSL_1_1_0-pre2~189
X-Git-Url: https://git.openssl.org/?p=openssl.git;a=commitdiff_plain;h=b859d70d4a04db2e3b39b5c86cb6750d3c5b9593

bn/asm/bn-c64xplus.asm: update commentary.

Reviewed-by: Rich Salz <rsalz@openssl.org>
---

diff --git a/crypto/bn/asm/bn-c64xplus.asm b/crypto/bn/asm/bn-c64xplus.asm
index 7cd58817e7..7b72bff4ac 100644
--- a/crypto/bn/asm/bn-c64xplus.asm
+++ b/crypto/bn/asm/bn-c64xplus.asm
@@ -284,8 +284,9 @@ _bn_mul_comba4:
 	.if	0
 	BNOP	sploopNxM?,3
 	;; Above mentioned m*2*(n+1)+10 does not apply in n=m=4 case,
-	;; because of read-after-write penalties, it's rather
-	;; n*2*(n+3)+10, or 66 cycles [plus various overheads]...
+	;; because of low-counter effect, when prologue phase finishes
+	;; before SPKERNEL instruction is reached. As result it's 25%
+	;; slower than expected...
 	MVK	4,B0		; N, RILC
 ||	MVK	4,A0		; M, outer loop counter
 ||	MV	ARG1,A5		; copy ap