From 2bfe61c33b99bd5ebb2e4616a6e8ac5790ff4c4f Mon Sep 17 00:00:00 2001
From: Marco Costalba <mcostalba@gmail.com>
Date: Mon, 7 Apr 2014 16:02:24 +0200
Subject: [PATCH] Add PEXT software implementation

For development/debug purposes.

No functional change.
---
 src/bitboard.cpp | 17 +++++++++++++++++
 src/bitboard.h   |  2 ++
 2 files changed, 19 insertions(+)

diff --git a/src/bitboard.cpp b/src/bitboard.cpp
index bfacc412..27ba6574 100644
--- a/src/bitboard.cpp
+++ b/src/bitboard.cpp
@@ -79,6 +79,23 @@ namespace {
   }
 }
 
+
+/// Intel PEXT (parallel extraction) software implementation
+Bitboard pext(Bitboard b, Bitboard mask) {
+
+  Bitboard res = 0;
+
+  for (Bitboard bb = 1; mask; bb += bb)
+  {
+      if (b & mask & -mask)
+          res |= bb;
+
+      mask &= mask - 1;
+  }
+  return res;
+}
+
+
 /// lsb()/msb() finds the least/most significant bit in a non-zero bitboard.
 /// pop_lsb() finds and clears the least significant bit in a non-zero bitboard.
 
diff --git a/src/bitboard.h b/src/bitboard.h
index 3ff0408a..140867fa 100644
--- a/src/bitboard.h
+++ b/src/bitboard.h
@@ -23,6 +23,8 @@
 
 #include "types.h"
 
+extern Bitboard pext(Bitboard b, Bitboard mask);
+
 namespace Bitboards {
 
 void init();
-- 
2.39.2