From f4d02ecdbf54987a0bada20fe8f8537e90c051d8 Mon Sep 17 00:00:00 2001
From: Konstantin Ritt <ritt.ks@gmail.com>
Date: Tue, 10 Apr 2012 18:00:32 +0300
Subject: [PATCH] optimize canonicalOrderHelper() for generic case

if there is no need to swap codepoints A and B,
then we proceeding with advance to the next codepoint B
that becomes A, and some next codepoint C becomes B;
in such case we can easily skip the re-calculations for A
by using previously calculated results for B

Change-Id: I5c63589c274acaddf0f6a4cb1e0608d352a0c1b3
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>
---
 src/corelib/tools/qchar.cpp | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/src/corelib/tools/qchar.cpp b/src/corelib/tools/qchar.cpp
index e3d6c60..1730418 100644
--- a/src/corelib/tools/qchar.cpp
+++ b/src/corelib/tools/qchar.cpp
@@ -1526,10 +1526,14 @@ static void canonicalOrderHelper(QString *str, QChar::UnicodeVersion version, in
 {
     QString &s = *str;
     const int l = s.length()-1;
+
+    uint u1, u2;
+    ushort c1, c2;
+
     int pos = from;
     while (pos < l) {
         int p2 = pos+1;
-        uint u1 = s.at(pos).unicode();
+        u1 = s.at(pos).unicode();
         if (QChar(u1).isHighSurrogate()) {
             ushort low = s.at(p2).unicode();
             if (QChar(low).isLowSurrogate()) {
@@ -1539,7 +1543,10 @@ static void canonicalOrderHelper(QString *str, QChar::UnicodeVersion version, in
                 ++p2;
             }
         }
-        uint u2 = s.at(p2).unicode();
+        c1 = 0;
+
+    advance:
+        u2 = s.at(p2).unicode();
         if (QChar(u2).isHighSurrogate() && p2 < l) {
             ushort low = s.at(p2+1).unicode();
             if (QChar(low).isLowSurrogate()) {
@@ -1548,7 +1555,7 @@ static void canonicalOrderHelper(QString *str, QChar::UnicodeVersion version, in
             }
         }
 
-        ushort c2 = 0;
+        c2 = 0;
         {
             const QUnicodeTables::Properties *p = qGetProp(u2);
             if (p->unicodeVersion <= version && p->unicodeVersion != QChar::Unicode_Unassigned)
@@ -1559,8 +1566,7 @@ static void canonicalOrderHelper(QString *str, QChar::UnicodeVersion version, in
             continue;
         }
 
-        ushort c1 = 0;
-        {
+        if (c1 == 0) {
             const QUnicodeTables::Properties *p = qGetProp(u1);
             if (p->unicodeVersion <= version && p->unicodeVersion != QChar::Unicode_Unassigned)
                 c1 = p->combiningClass;
@@ -1590,6 +1596,16 @@ static void canonicalOrderHelper(QString *str, QChar::UnicodeVersion version, in
             ++pos;
             if (QChar::requiresSurrogates(u1))
                 ++pos;
+
+            u1 = u2;
+            c1 = c2; // != 0
+            p2 = pos + 1;
+            if (QChar::requiresSurrogates(u1))
+                ++p2;
+            if (p2 > l)
+                break;
+
+            goto advance;
         }
     }
 }
-- 
2.7.4