From: Marco Costalba <mcostalba@gmail.com>
Date: Mon, 15 Jul 2013 18:50:24 +0000 (+0200)
Subject: Better annotate unlikely conditions
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=cbb1a8ed31679fe32d2694448a10b031390a32b3

Better annotate unlikely conditions

And in case of gcc we win also a small
speed optimization due to better branch
prediction.

No functional change.
---

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 8bbd0bff..bb9a2f97 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -823,7 +823,7 @@ Value do_evaluate(const Position& pos, Value& margin) {
                 // If there is an enemy rook or queen attacking the pawn from behind,
                 // add all X-ray attacks by the rook or queen. Otherwise consider only
                 // the squares in the pawn's path attacked or occupied by the enemy.
-                if (   (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN)) // Unlikely
+                if (    unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
                     && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
                     unsafeSquares = squaresToQueen;
                 else
diff --git a/src/search.cpp b/src/search.cpp
index f47e601b..eae2ea27 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1454,7 +1454,7 @@ moves_loop: // When in check and at SpNode search starts from here
                        | (attacks_bb<BISHOP>(m2to, occ) & pos.pieces(color_of(pc), QUEEN, BISHOP));
 
         // Verify attackers are triggered by our move and not already existing
-        if (xray && (xray & ~pos.attacks_from<QUEEN>(m2to))) // Unlikely xray
+        if (unlikely(xray) && (xray & ~pos.attacks_from<QUEEN>(m2to)))
             return true;
     }
 
diff --git a/src/types.h b/src/types.h
index 444d7afd..8eb99455 100644
--- a/src/types.h
+++ b/src/types.h
@@ -71,6 +71,14 @@
 #  define FORCE_INLINE  inline
 #endif
 
+#ifdef __GNUC__
+#  define likely(x)   __builtin_expect(!!(x), 1)
+#  define unlikely(x) __builtin_expect(!!(x), 0)
+#else
+#  define likely(x)   (x)
+#  define unlikely(x) (x)
+#endif
+
 #if defined(USE_POPCNT)
 const bool HasPopCnt = true;
 #else