Use more common (and readable) names for branch prediction hints

bson/bson-inl.h

@@ -172,7 +172,7 @@ namespace mongo {
     }
 
     inline BSONObj BSONElement::embeddedObjectUserCheck() const {
-        MONGOIF ( isABSONObj() )
+        if ( MONGO_likely(isABSONObj()) )
             return BSONObj(value());
         stringstream ss;
         ss << "invalid parameter: expected an object (" << fieldName() << ")";

bson/bsonobjiterator.h

@@ -37,7 +37,7 @@ namespace mongo {
         */
         BSONObjIterator(const BSONObj& jso) {
             int sz = jso.objsize();
-            MONGO_IF ( sz == 0 ) {
+            if ( MONGO_unlikely(sz == 0) ) {
                 _pos = _theend = 0;
                 return;
             }

bson/inline_decls.h

@@ -37,11 +37,11 @@ namespace mongo {
 
 #if !defined(__GNUC__)
 
-// branch prediction.  indicate we expect to enter the if statement body
-# define MONGOIF(x) if( (x) )
+// branch prediction.  indicate we expect to be true
+# define MONGO_likely(x) ((bool)(x))
 
-// branch prediction.  indicate we expect to not enter the if statement body
-# define MONGO_IF(x) if( (x) )
+// branch prediction.  indicate we expect to be false
+# define MONGO_unlikely(x) ((bool)(x))
 
 # if defined(_WIN32)
     // prefetch data from memory
@@ -56,8 +56,8 @@ namespace mongo {
 
 #else
 
-# define MONGOIF(x) if( __builtin_expect((x), 1) )
-# define MONGO_IF(x) if( __builtin_expect((x), 0) )
+# define MONGO_likely(x) ( __builtin_expect((bool)(x), 1) )
+# define MONGO_unlikely(x) ( __builtin_expect((bool)(x), 0) )
 
     inline void prefetch(void *p) { 
         __builtin_prefetch(p);

db/dur_preplogbuffer.cpp

@@ -60,7 +60,7 @@ namespace mongo {
             size_t ofs = 1;
             MongoMMF *mmf = findMMF_inlock(i->start(), /*out*/ofs);
 
-            _IF( !mmf->willNeedRemap() ) {
+            if( unlikely(!mmf->willNeedRemap()) ) {
                 // tag this mmf as needed a remap of its private view later.
                 // usually it will already be dirty/already set, so we do the if above first
                 // to avoid possibility of cpu cache line contention
@@ -97,7 +97,7 @@ namespace mongo {
 #endif
             bb.appendBuf(i->start(), e.len);
 
-            _IF (e.len != (unsigned)i->length()) {
+            if (unlikely(e.len != (unsigned)i->length())) {
                 log() << "journal info splitting prepBasicWrite at boundary" << endl;
 
                 // This only happens if we write to the last byte in a file and

db/ops/query.cpp

@@ -101,7 +101,7 @@ namespace mongo {
         int start = 0;
         int n = 0;
 
-        _IF ( !cc ) {
+        if ( unlikely(!cc) ) {
             log() << "getMore: cursorid not found " << ns << " " << cursorid << endl;
             cursorid = 0;
             resultFlags = ResultFlag_CursorNotFound;

server.h

@@ -13,9 +13,9 @@
 
 /* Note: do not clutter code with these -- ONLY use in hot spots / significant loops. */
 
-// branch prediction.  indicate we expect to enter the if statement body
-#define IF MONGOIF
+// branch prediction.  indicate we expect to be true
+#define likely MONGO_likely
 
-// branch prediction.  indicate we expect to not enter the if statement body
-#define _IF MONGO_IF
+// branch prediction.  indicate we expect to be false
+#define unlikely MONGO_unlikely
 

util/alignedbuilder.h

@@ -101,7 +101,7 @@ namespace mongo {
         inline char* grow(unsigned by) {
             unsigned oldlen = _len;
             _len += by;
-            MONGO_IF ( _len > _p._size ) {
+            if (MONGO_unlikely( _len > _p._size )) {
                 growReallocate(oldlen);
             }
             return _p._data + oldlen;

util/concurrency/rwlock.h

@@ -175,7 +175,7 @@ namespace mongo {
         pthread_rwlock_t _lock;
         const int _lowPriorityWaitMS;    
         static void check( int x ) {
-            MONGOIF( x == 0 )
+            if( likely(x == 0) )
                 return;
             log() << "pthread rwlock failed: " << x << endl;
             assert( x == 0 );

util/log.h

@@ -345,7 +345,7 @@ namespace mongo {
         return Logstream::get().prolog();
     }
 
-#define MONGO_LOG(level) MONGO_IF ( logLevel >= (level) ) log( level )
+#define MONGO_LOG(level) if ( MONGO_unlikely(logLevel >= (level)) ) log( level )
 #define LOG MONGO_LOG
 
     inline Nullstream& log( LogLevel l ) {