From c1954e6af6ec75d079ff94f7008cbe2da667392e Mon Sep 17 00:00:00 2001
From: Chris Vest <mr.chrisvest@gmail.com>
Date: Sun, 19 Mar 2017 09:11:08 +0100
Subject: [PATCH] Use branching for bounds checking

It turns out that branching code is faster than branch free code in this case.
CPUs are really good at branch prediction, I guess.
Measurements show the difference is very slight, but it is none the less there.
---
 .../impl/muninn/MuninnPageCursor.java         | 36 ++++++++++---------
 1 file changed, 20 insertions(+), 16 deletions(-)

diff --git a/community/io/src/main/java/org/neo4j/io/pagecache/impl/muninn/MuninnPageCursor.java b/community/io/src/main/java/org/neo4j/io/pagecache/impl/muninn/MuninnPageCursor.java
index d769380f1347..3e10541bfe14 100644
--- a/community/io/src/main/java/org/neo4j/io/pagecache/impl/muninn/MuninnPageCursor.java
+++ b/community/io/src/main/java/org/neo4j/io/pagecache/impl/muninn/MuninnPageCursor.java
@@ -392,19 +392,19 @@ long assertPagedFileStillMappedAndGetIdOfLastPage()
      */
     private long getBoundedPointer( int offset, int size )
     {
+        long p = pointer;
+        long can = p + offset;
         if ( boundsCheck )
         {
-            long can = pointer + offset;
-            long lim = pointer + pageSize - size;
-            long ref = Math.min( can, lim );
-            ref = Math.max( ref, pointer );
-            outOfBounds |= ref != can | lim < pointer;
-            return ref;
-        }
-        else
-        {
-            return pointer + offset;
+            if ( can + size > p + pageSize || can < p )
+            {
+                outOfBounds = true;
+                // Return the victim page when we are out of bounds, since at this point we can't tell if the pointer
+                // will be used for reading or writing.
+                return victimPage;
+            }
         }
+        return can;
     }
 
     /**
@@ -415,15 +415,19 @@ private long getBoundedPointer( int offset, int size )
      */
     private long nextBoundedPointer( int size )
     {
+        int offset = this.offset;
+        long can = pointer + offset;
         if ( boundsCheck )
         {
-            outOfBounds |= offset + size > pageSize;
-            return outOfBounds? pointer : pointer + offset;
-        }
-        else
-        {
-            return pointer + offset;
+            if ( offset + size > pageSize )
+            {
+                outOfBounds = true;
+                // Return the victim page when we are out of bounds, since at this point we can't tell if the pointer
+                // will be used for reading or writing.
+                return victimPage;
+            }
         }
+        return can;
     }
 
     @Override