From: Ivan Maidanski <ivmai@mail.ru>
Date: Fri, 25 Aug 2017 06:53:07 +0000 (+0300)
Subject: Simplify THREAD_TABLE_INDEX expression for Win32/64
X-Git-Tag: v8.0.0~594
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=e897b41dcf36148f61ce5ab7e4ec60ab5dae15ce;p=gc

Simplify THREAD_TABLE_INDEX expression for Win32/64
(fix commit 85fce54)

Windows thread Id rarely has non-zero highest half of DWORD, so
it is OK to use only the lowest one for hash value computation.

* win32_threads.c (THREAD_TABLE_INDEX): Remove (id>>16) from the
expression.
---

diff --git a/win32_threads.c b/win32_threads.c
index 7befb9bb..3cbdc22c 100644
--- a/win32_threads.c
+++ b/win32_threads.c
@@ -321,7 +321,7 @@ STATIC volatile LONG GC_max_thread_index = 0;
 # define THREAD_TABLE_SZ 256    /* Power of 2 (for speed). */
 #endif
 #define THREAD_TABLE_INDEX(id) /* id is of DWORD type */ \
-                (int)((((id) >> 16) ^ ((id) >> 8) ^ (id)) % THREAD_TABLE_SZ)
+                (int)((((id) >> 8) ^ (id)) % THREAD_TABLE_SZ)
 STATIC GC_thread GC_threads[THREAD_TABLE_SZ];
 
 /* It may not be safe to allocate when we register the first thread.    */