From: Eric Biggers <ebiggers3@gmail.com>
Date: Sat, 6 Sep 2014 16:54:16 +0000 (-0500)
Subject: lz_copy(): Unroll first iteration
X-Git-Tag: v1.7.2~28
X-Git-Url: https://wimlib.net/git/?p=wimlib;a=commitdiff_plain;h=0158ecdaa9e7475a75799f369468f9af5a8ce4ea;hp=e02ea0a6b4aec8b3475ea24522f254affb6cfcd3

lz_copy(): Unroll first iteration

Most matches are short, so 1 iteration is the most common case.
Use separate branch for this.
---

diff --git a/include/wimlib/decompress_common.h b/include/wimlib/decompress_common.h
index da15fd1e..3f3742a0 100644
--- a/include/wimlib/decompress_common.h
+++ b/include/wimlib/decompress_common.h
@@ -277,13 +277,22 @@ lz_copy(u8 *dst, u32 length, u32 offset, const u8 *winend)
 			unsigned long v;
 		} _packed_attribute;
 
-		const u8 *end = dst + length;
-		do {
-			unsigned long v = ((struct ulong_wrapper *)src)->v;
-			((struct ulong_wrapper *)dst)->v = v;
-			dst += sizeof(unsigned long);
-			src += sizeof(unsigned long);
-		} while (dst < end);
+		const u8 * const end = dst + length;
+		unsigned long v;
+
+		v = ((struct ulong_wrapper *)src)->v;
+		((struct ulong_wrapper *)dst)->v = v;
+		dst += sizeof(unsigned long);
+		src += sizeof(unsigned long);
+
+		if (dst < end) {
+			do {
+				v = ((struct ulong_wrapper *)src)->v;
+				((struct ulong_wrapper *)dst)->v = v;
+				dst += sizeof(unsigned long);
+				src += sizeof(unsigned long);
+			} while (dst < end);
+		}
 
 		return;
 	}