Speed up ScriptRun::getPairIndex

Noted as a hot spot in the callgrind of
test-files/loperf/091_fdo#39372.odt

The idea for the lookup tables is credited to mjayfrancis.

This takes it from 1.8 billion instructions to 1.1 billion instructions.

This change has been submitted upstream (along with other changes
to these source files that have not yet been pushed there)
in ICU ticket:
    http://bugs.icu-project.org/trac/ticket/11577

Change-Id: I917bdea4263320f9e88207657b7f3140d95ae2b8
Reviewed-on: https://gerrit.libreoffice.org/14834Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

vcl/generic/glyphs/scrptrun.cxx

@@ -33,103 +33,98 @@
  *   created on: 10/17/2001
  *   created by: Eric R. Mader
  */
-
+/**
+  * This file is largely copied from the ICU project,
+  * under folder source/extra/scrptrun/scrptrun.cpp
+  */
 #include "unicode/utypes.h"
 #include "unicode/uscript.h"
 
 #include "scrptrun.h"
+#include <algorithm>
 
-#define ARRAY_SIZE(array) (sizeof array  / sizeof array[0])
-
-namespace vcl {
-
-const char ScriptRun::fgClassID=0;
-
-UChar32 ScriptRun::pairedChars[] = {
-    0x0028, 0x0029, // ascii paired punctuation
-    0x003c, 0x003e,
-    0x005b, 0x005d,
-    0x007b, 0x007d,
-    0x00ab, 0x00bb, // guillemets
-    0x2018, 0x2019, // general punctuation
-    0x201c, 0x201d,
-    0x2039, 0x203a,
-    0x3008, 0x3009, // chinese paired punctuation
-    0x300a, 0x300b,
-    0x300c, 0x300d,
-    0x300e, 0x300f,
-    0x3010, 0x3011,
-    0x3014, 0x3015,
-    0x3016, 0x3017,
-    0x3018, 0x3019,
-    0x301a, 0x301b
-};
-
-const int32_t ScriptRun::pairedCharCount = ARRAY_SIZE(pairedChars);
-const int32_t ScriptRun::pairedCharPower = 1 << highBit(pairedCharCount);
-const int32_t ScriptRun::pairedCharExtra = pairedCharCount - pairedCharPower;
+namespace {
 
-int8_t ScriptRun::highBit(int32_t value)
+struct PairIndices
 {
-    if (value <= 0) {
-        return -32;
-    }
-
-    int8_t bit = 0;
-
-    if (value >= 1 << 16) {
-        value >>= 16;
-        bit += 16;
-    }
-
-    if (value >= 1 << 8) {
-        value >>= 8;
-        bit += 8;
-    }
+    int8_t ma00[0xff];
+    int8_t ma20[0x7f];
+    int8_t ma30[0x7f];
 
-    if (value >= 1 << 4) {
-        value >>= 4;
-        bit += 4;
-    }
-
-    if (value >= 1 << 2) {
-        value >>= 2;
-        bit += 2;
+    PairIndices()
+    {
+        std::fill_n(ma00, 0xff, -1);
+        std::fill_n(ma20, 0x7f, -1);
+        std::fill_n(ma30, 0x7f, -1);
+
+        // characters in the range 0x0000 - 0x007e (inclusive)
+        // ascii paired punctuation
+        ma00[0x28] =  0;
+        ma00[0x29] =  1;
+        ma00[0x3c] =  2;
+        ma00[0x3e] =  3;
+        ma00[0x5b] =  4;
+        ma00[0x5d] =  5;
+        ma00[0x7b] =  6;
+        ma00[0x7d] =  7;
+        // guillemets
+        ma00[0xab] =  8;
+        ma00[0xbb] =  9;
+
+        // characters in the range 0x2000 - 0x207e (inclusive)
+        // general punctuation
+        ma20[0x18] = 10;
+        ma20[0x19] = 11;
+        ma20[0x1c] = 12;
+        ma20[0x1d] = 13;
+        ma20[0x39] = 14;
+        ma20[0x3a] = 15;
+
+        // characters in the range 0x3000 - 0x307e (inclusive)
+        // chinese paired punctuation
+        ma30[0x08] = 16;
+        ma30[0x09] = 17;
+        ma30[0x0a] = 18;
+        ma30[0x0b] = 19;
+        ma30[0x0c] = 20;
+        ma30[0x0d] = 21;
+        ma30[0x0e] = 22;
+        ma30[0x0f] = 23;
+        ma30[0x10] = 24;
+        ma30[0x11] = 25;
+        ma30[0x14] = 26;
+        ma30[0x15] = 27;
+        ma30[0x16] = 28;
+        ma30[0x17] = 29;
+        ma30[0x18] = 30;
+        ma30[0x19] = 31;
+        ma30[0x1a] = 32;
+        ma30[0x1b] = 33;
+    }
+
+    inline int32_t getPairIndex(UChar32 ch) const
+    {
+        if (ch < 0xff)
+            return ma00[ch];
+        if (ch >= 0x2000 && ch < 0x207f)
+            return ma20[ch - 0x2000];
+        if (ch >= 0x3000 && ch < 0x307f)
+            return ma30[ch - 0x3000];
+        return -1;
     }
 
-    if (value >= 1 << 1) {
-        value >>= 1;
-        bit += 1;
-    }
+};
 
-    return bit;
 }
 
-int32_t ScriptRun::getPairIndex(UChar32 ch)
-{
-    int32_t probe = pairedCharPower;
-    int32_t index = 0;
-
-    if (ch >= pairedChars[pairedCharExtra]) {
-        index = pairedCharExtra;
-    }
+static const PairIndices gPairIndices;
 
-    while (probe > (1 << 0)) {
-        probe >>= 1;
 
-        if (ch >= pairedChars[index + probe]) {
-            index += probe;
-        }
-    }
-
-    if (pairedChars[index] != ch) {
-        index = -1;
-    }
+namespace vcl {
 
-    return index;
-}
+const char ScriptRun::fgClassID=0;
 
-UBool ScriptRun::sameScript(int32_t scriptOne, int32_t scriptTwo)
+static inline UBool sameScript(int32_t scriptOne, int32_t scriptTwo)
 {
     return scriptOne <= USCRIPT_INHERITED || scriptTwo <= USCRIPT_INHERITED || scriptOne == scriptTwo;
 }
@@ -165,7 +160,7 @@ UBool ScriptRun::next()
         }
 
         UScriptCode sc = uscript_getScript(ch, &error);
-        int32_t pairIndex = getPairIndex(ch);
+        int32_t pairIndex = gPairIndices.getPairIndex(ch);
 
         // Paired character handling:
 

vcl/generic/glyphs/scrptrun.h

@@ -103,8 +103,6 @@ public:
 
 private:
 
-    static UBool sameScript(int32_t scriptOne, int32_t scriptTwo);
-
     int32_t charStart;
     int32_t charLimit;
     const UChar *charArray;
@@ -116,14 +114,6 @@ private:
     std::vector<ParenStackEntry> parenStack;
     int32_t parenSP;
 
-    static int8_t highBit(int32_t value);
-    static int32_t getPairIndex(UChar32 ch);
-
-    static UChar32 pairedChars[];
-    static const int32_t pairedCharCount;
-    static const int32_t pairedCharPower;
-    static const int32_t pairedCharExtra;
-
     /**
      * The address of this static class variable serves as this class's ID
      * for ICU "poor man's RTTI".