From 38c3945de300851757d0dd76182ee28aaf8253a4 Mon Sep 17 00:00:00 2001
From: Nick Terrell <terrelln@fb.com>
Date: Tue, 30 Jul 2019 23:40:58 -0700
Subject: [PATCH] [lz4hc] Only allow chain swapping forwards

When the match is very long and found quickly, we can do
matchLength * nbCompares iterations through the chain
swapping, which can really slow down compression.
---
 lib/lz4hc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/lz4hc.c b/lib/lz4hc.c
index 596888a..0608ec6 100644
--- a/lib/lz4hc.c
+++ b/lib/lz4hc.c
@@ -314,7 +314,7 @@ LZ4HC_InsertAndGetWiderMatch (
             if (matchIndex + (U32)longest <= ipIndex) {
                 U32 distanceToNextMatch = 1;
                 int pos;
-                for (pos = 0; pos <= longest - MINMATCH; ++pos) {
+                for (pos = matchChainPos; pos <= longest - MINMATCH; ++pos) {
                     U32 const candidateDist = DELTANEXTU16(chainTable, matchIndex + (U32)pos);
                     if (candidateDist > distanceToNextMatch) {
                         distanceToNextMatch = candidateDist;
-- 
2.7.4