From: Denys Vlasenko <vda.linux@googlemail.com>
Date: Mon, 18 Jan 2010 04:22:34 +0000 (+0100)
Subject: diff: defeat gcc's optimization
X-Git-Tag: 1_16_0~31
X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=032bf6553346537cb02d0406c05548c8aa23c81f;p=oweals%2Fbusybox.git

diff: defeat gcc's optimization

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
---

diff --git a/editors/diff.c b/editors/diff.c
index af6917a03..b89bbc1dc 100644
--- a/editors/diff.c
+++ b/editors/diff.c
@@ -435,7 +435,10 @@ static int *create_J(FILE_and_pos_t ft[2], int nlen[2], off_t *ix[2])
 			tok = read_token(&ft[i], tok);
 			if (!(tok & TOK_EMPTY)) {
 				/* Hash algorithm taken from Robert Sedgewick, Algorithms in C, 3d ed., p 578. */
-				hash = hash * 128 - hash + TOK2CHAR(tok);
+				/*hash = hash * 128 - hash + TOK2CHAR(tok);
+				 * gcc insists on optimizing above to "hash * 127 + ...", thus... */
+				unsigned o = hash - TOK2CHAR(tok);
+				hash = hash * 128 - o; /* we want SPEED here */
 				continue;
 			}
 			if (nlen[i]++ == sz) {