[POSIX] Use access() instead of stat() in FileSystem::fileExists()

https://bugs.webkit.org/show_bug.cgi?id=185882

Reviewed by Geoffrey Garen.

Use access() instead of stat() in FileSystem::fileExists(). stat() returns a lot of information we
do not leverage and local benchmarking on macOS shows access() being > 80% faster than stat():
stat: 0.31567 (lower is better)
access: 0.16074 (lower is better)
stat: 0.303665 (lower is better)
access: 0.165468 (lower is better)

* platform/posix/FileSystemPOSIX.cpp:
(WebCore::FileSystem::fileExists):


Canonical link: https://commits.webkit.org/201337@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@232088 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Source/WebCore/ChangeLog

@@ -1,3 +1,20 @@
+2018-05-22  Chris Dumez  <cdumez@apple.com>
+
+        [POSIX] Use access() instead of stat() in FileSystem::fileExists()
+        https://bugs.webkit.org/show_bug.cgi?id=185882
+
+        Reviewed by Geoffrey Garen.
+
+        Use access() instead of stat() in FileSystem::fileExists(). stat() returns a lot of information we
+        do not leverage and local benchmarking on macOS shows access() being > 80% faster than stat():
+        stat: 0.31567 (lower is better)
+        access: 0.16074 (lower is better)
+        stat: 0.303665 (lower is better)
+        access: 0.165468 (lower is better)
+
+        * platform/posix/FileSystemPOSIX.cpp:
+        (WebCore::FileSystem::fileExists):
+
 2018-05-22  Brent Fulgham  <bfulgham@apple.com>
 
         Avoid keeping FormState alive longer than necessary

Source/WebCore/platform/posix/FileSystemPOSIX.cpp

@@ -58,10 +58,7 @@ bool fileExists(const String& path)
     if (!fsRep.data() || fsRep.data()[0] == '\0')
         return false;
 
-    struct stat fileInfo;
-
-    // stat(...) returns 0 on successful stat'ing of the file, and non-zero in any case where the file doesn't exist or cannot be accessed
-    return !stat(fsRep.data(), &fileInfo);
+    return access(fsRep.data(), F_OK) != -1;
 }
 
 bool deleteFile(const String& path)