Add likely/unlikely defines for using built-in function provided by GCC

amxmodx/amxmodx.cpp

@@ -43,7 +43,7 @@ static cell AMX_NATIVE_CALL get_xvar_id(AMX *amx, cell *params)
 
 	for (auto var : g_sInaccessibleXVars)
 	{
-		if (!strcmp(sName, var))
+		if (likely(!strcmp(sName, var)))
 		{
 			return -1;
 		}

amxmodx/amxmodx.h

@@ -53,6 +53,7 @@
 #include "CFrameAction.h"
 #include <amxmodx_version.h>
 #include <HLTypeConversion.h>
+#include "extdef.h"
 
 #define AMXXLOG_Log g_log.Log
 #define AMXXLOG_Error g_log.LogError

amxmodx/extdef.h

@@ -0,0 +1,10 @@
+#pragma once
+
+// Manual branch optimization for GCC 3.0.0 and newer
+#if !defined(__GNUC__) || __GNUC__ < 3
+#define likely(x) (x)
+#define unlikely(x) (x)
+#else
+#define likely(x) __builtin_expect(!!(x), 1)
+#define unlikely(x) __builtin_expect(!!(x), 0)
+#endif

amxmodx/msvc12/amxmodx_mm.vcxproj

@@ -429,6 +429,7 @@ md -p JIT 2>NUL
     <ClInclude Include="..\CVault.h" />
     <ClInclude Include="..\datastructs.h" />
     <ClInclude Include="..\debugger.h" />
+    <ClInclude Include="..\extdef.h" />
     <ClInclude Include="..\fakemeta.h" />
     <ClInclude Include="..\format.h" />
     <ClInclude Include="..\gameconfigs.h" />

amxmodx/msvc12/amxmodx_mm.vcxproj.filters

@@ -584,6 +584,9 @@
     <ClInclude Include="..\CFrameAction.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="..\extdef.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <ResourceCompile Include="..\version.rc">