X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fmovegen.cpp;h=cf938dadc27d89a93b78b780e6a884f8ccd03d5e;hp=f4ea0c6e9e5bb36d616039b858668c2c765fc951;hb=72289fcfab9750db76d9dab730a7f0c5f405a236;hpb=146bb2dfa730841d8c00c162076423437af1377d

diff --git a/src/movegen.cpp b/src/movegen.cpp
index f4ea0c6e..cf938dad 100644
--- a/src/movegen.cpp
+++ b/src/movegen.cpp
@@ -31,16 +31,37 @@
 ////
 
 namespace {
+
+  inline Bitboard forward_white(Bitboard b) { return b << 8; }
+  inline Bitboard forward_right_white(Bitboard b) { return b << 9; }
+  inline Bitboard forward_left_white(Bitboard b) { return b << 7; }
+
+  inline Bitboard forward_black(Bitboard b) { return b >> 8; }
+  inline Bitboard forward_right_black(Bitboard b) { return b >> 7; }
+  inline Bitboard forward_left_black(Bitboard b) { return b >> 9; }
+
+  struct PawnOffsets {
+
+      Bitboard Rank3BB, Rank8BB;
+      SquareDelta DELTA_N, DELTA_NE, DELTA_NW;
+      Color us, them;
+      typedef Bitboard (*Shift_fn)(Bitboard b);
+      Shift_fn forward, forward_left, forward_right;
+  };
+  const PawnOffsets WhitePawnOffsets = { Rank3BB, Rank8BB, DELTA_N, DELTA_NE, DELTA_NW, WHITE,
+                                         BLACK, &forward_white, forward_left_white, forward_right_white };
+
+  const PawnOffsets BlackPawnOffsets = { Rank6BB, Rank1BB, DELTA_S, DELTA_SE, DELTA_SW, BLACK,
+                                         WHITE, &forward_black, &forward_left_black, &forward_right_black };
   
-  int generate_white_pawn_captures(const Position&, MoveStack*);
-  int generate_black_pawn_captures(const Position&, MoveStack*);
-  int generate_white_pawn_noncaptures(const Position&, MoveStack*);
-  int generate_black_pawn_noncaptures(const Position&, MoveStack*);
+  int generate_pawn_captures(const PawnOffsets&, const Position&, MoveStack*);  
+  int generate_pawn_noncaptures(const PawnOffsets&, const Position&, MoveStack*);
+  int generate_pawn_checks(const PawnOffsets&, const Position&, Bitboard dc, Square ksq, MoveStack*, int n);
   int generate_piece_moves(PieceType, const Position&, MoveStack*, Color side, Bitboard t);
   int generate_castle_moves(const Position&, MoveStack*, Color us);
 
   int generate_piece_checks(PieceType pce, const Position& pos, Bitboard target,
-                            Bitboard dc, Square ksq, MoveStack* mlist);
+                            Bitboard dc, Square ksq, MoveStack* mlist, int n);
 }
 
 
@@ -62,9 +83,9 @@ int generate_captures(const Position& pos, MoveStack* mlist) {
   int n;
 
   if (us == WHITE)
-      n = generate_white_pawn_captures(pos, mlist);
+      n = generate_pawn_captures(WhitePawnOffsets, pos, mlist);
   else
-      n = generate_black_pawn_captures(pos, mlist);
+      n = generate_pawn_captures(BlackPawnOffsets, pos, mlist);
 
   for (PieceType pce = KNIGHT; pce <= KING; pce++)
       n += generate_piece_moves(pce, pos, mlist+n, us, target);
@@ -86,9 +107,9 @@ int generate_noncaptures(const Position& pos, MoveStack *mlist) {
   int n;
 
   if (us == WHITE)
-      n = generate_white_pawn_noncaptures(pos, mlist);
+      n = generate_pawn_noncaptures(WhitePawnOffsets, pos, mlist);
   else
-      n = generate_black_pawn_noncaptures(pos, mlist);
+      n = generate_pawn_noncaptures(BlackPawnOffsets, pos, mlist);
 
   for (PieceType pce = KNIGHT; pce <= KING; pce++)
       n += generate_piece_moves(pce, pos, mlist+n, us, target);
@@ -107,146 +128,45 @@ int generate_checks(const Position& pos, MoveStack* mlist, Bitboard dc) {
   assert(pos.is_ok());
   assert(!pos.is_check());
 
-  Color us, them;
-  Square ksq, from, to;
-  Bitboard empty, b1, b2, b3;
-  int n = 0;
-
-  us = pos.side_to_move();
-  them = opposite_color(us);
+  int n;
+  Color us = pos.side_to_move();
+  Square ksq = pos.king_square(opposite_color(us));
 
-  ksq = pos.king_square(them);
-  assert(pos.piece_on(ksq) == king_of_color(them));
+  assert(pos.piece_on(ksq) == king_of_color(opposite_color(us)));
 
   dc = pos.discovered_check_candidates(us);
-  empty = pos.empty_squares();
-  
-  // Pawn moves.  This is somewhat messy, and we use separate code for white
-  // and black, because we can't shift by negative numbers in C/C++.  :-(
-
-  if (us == WHITE)
-  {
-    // Pawn moves which give discovered check. This is possible only if the 
-    // pawn is not on the same file as the enemy king, because we don't 
-    // generate captures.
 
-    // Find all friendly pawns not on the enemy king's file
-    b1 = pos.pawns(us) & ~file_bb(ksq);
-
-    // Discovered checks, single pawn pushes
-    b2 = b3 = ((b1 & dc) << 8) & ~Rank8BB & empty;
-    while (b3)
-    {
-        to = pop_1st_bit(&b3);
-        mlist[n++].move = make_move(to - DELTA_N, to);
-    }
-
-    // Discovered checks, double pawn pushes
-    b3 = ((b2 & Rank3BB) << 8) & empty;
-    while (b3)
-    {
-        to = pop_1st_bit(&b3);
-        mlist[n++].move = make_move(to - DELTA_N - DELTA_N, to);
-    }
-
-    // Direct checks. These are possible only for pawns on neighboring files
-    // of the enemy king
-
-    b1 &= (~dc & neighboring_files_bb(ksq));
-
-    // Direct checks, single pawn pushes
-    b2 = (b1 << 8) & empty;
-    b3 = b2 & pos.black_pawn_attacks(ksq);
-    while(b3)
-    {
-        to = pop_1st_bit(&b3);
-        mlist[n++].move = make_move(to - DELTA_N, to);
-    }
-
-    // Direct checks, double pawn pushes
-    b3 = ((b2 & Rank3BB) << 8) & empty & pos.black_pawn_attacks(ksq);
-    while (b3)
-    {
-        to = pop_1st_bit(&b3);
-        mlist[n++].move = make_move(to - DELTA_N - DELTA_N, to);
-    }
-  }
-  else { // (us == BLACK)
-
-    // Pawn moves which give discovered check.  This is possible only if the 
-    // pawn is not on the same file as the enemy king, because we don't 
-    // generate captures.
-
-    // Find all friendly pawns not on the enemy king's file:
-    b1 = pos.pawns(us) & ~file_bb(ksq);
-
-    // Discovered checks, single pawn pushes
-    b2 = b3 = ((b1 & dc) >> 8) & ~Rank1BB & empty;
-    while (b3)
-    {
-        to = pop_1st_bit(&b3);
-        mlist[n++].move = make_move(to - DELTA_S, to);
-    }
-
-    // Discovered checks, double pawn pushes
-    b3 = ((b2 & Rank6BB) >> 8) & empty;
-    while (b3)
-    {
-        to = pop_1st_bit(&b3);
-        mlist[n++].move = make_move(to - DELTA_S - DELTA_S, to);
-    }
-
-    // Direct checks.  These are possible only for pawns on neighboring files
-    // of the enemy king
-
-    b1 &= (~dc & neighboring_files_bb(ksq));
-
-    // Direct checks, single pawn pushes:
-    b2 = (b1 >> 8) & empty;
-    b3 = b2 & pos.white_pawn_attacks(ksq);
-    while (b3)
-    {
-        to = pop_1st_bit(&b3);
-        mlist[n++].move = make_move(to - DELTA_S, to);
-    }
-
-    // Direct checks, double pawn pushes
-    b3 = ((b2 & Rank6BB) >> 8) & empty & pos.black_pawn_attacks(ksq);
-    while (b3)
-    {
-        to = pop_1st_bit(&b3);
-        mlist[n++].move = make_move(to - DELTA_S - DELTA_S, to);
-    }
-  }
+  // Pawn moves
+  if (us == WHITE)    
+     n = generate_pawn_checks(WhitePawnOffsets, pos, dc, ksq, mlist, 0);
+  else
+     n = generate_pawn_checks(BlackPawnOffsets, pos, dc, ksq, mlist, 0);
 
-  // Knight moves
-  b1 = pos.knights(us);
-  if (b1)
-      n += generate_piece_checks(KNIGHT, pos, b1, dc, ksq, mlist);
+  // Pieces moves
+  Bitboard b = pos.knights(us);
+  if (b)
+      n = generate_piece_checks(KNIGHT, pos, b, dc, ksq, mlist, n);
 
-  // Bishop moves
-  b1 = pos.bishops(us);
-  if (b1)
-      n += generate_piece_checks(BISHOP, pos, b1, dc, ksq, mlist);
+  b = pos.bishops(us);
+  if (b)
+      n = generate_piece_checks(BISHOP, pos, b, dc, ksq, mlist, n);
 
-  // Rook moves
-  b1 = pos.rooks(us);
-  if (b1)
-      n += generate_piece_checks(ROOK, pos, b1, dc, ksq, mlist);
+  b = pos.rooks(us);
+  if (b)
+      n = generate_piece_checks(ROOK, pos, b, dc, ksq, mlist, n);
 
-  // Queen moves
-  b1 = pos.queens(us);
-  if (b1)
-      n += generate_piece_checks(QUEEN, pos, b1, dc, ksq, mlist);
+  b = pos.queens(us);
+  if (b)
+      n = generate_piece_checks(QUEEN, pos, b, dc, ksq, mlist, n);
 
   // King moves
-  from = pos.king_square(us);
+  Square from = pos.king_square(us);
   if (bit_is_set(dc, from))
   {
-      b1 = pos.king_attacks(from) & empty & ~QueenPseudoAttacks[ksq];
-      while (b1)
+      b = pos.king_attacks(from) & pos.empty_squares() & ~QueenPseudoAttacks[ksq];
+      while (b)
       {
-          to = pop_1st_bit(&b1);
+          Square to = pop_1st_bit(&b);
           mlist[n++].move = make_move(from, to);
       }
   }
@@ -704,65 +624,68 @@ Move generate_move_if_legal(const Position &pos, Move m, Bitboard pinned) {
 
 namespace {
 
-  int generate_white_pawn_captures(const Position &pos, MoveStack *mlist) {
+  int generate_pawn_captures(const PawnOffsets& ofs, const Position& pos, MoveStack* mlist) {
 
-    Bitboard pawns = pos.pawns(WHITE);
-    Bitboard enemyPieces = pos.pieces_of_color(BLACK);
+    Bitboard pawns = pos.pawns(ofs.us);
+    Bitboard enemyPieces = pos.pieces_of_color(ofs.them);
     Square sq;
     int n = 0;
 
-    // Captures in the a1-h8 direction
-    Bitboard b1 = (pawns << 9) & ~FileABB & enemyPieces;
+    // Captures in the a1-h8 (a8-h1 for black) direction
+    Bitboard b1 = (ofs.forward_right)(pawns) & ~FileABB & enemyPieces;
 
     // Capturing promotions
-    Bitboard b2 = b1 & Rank8BB;
+    Bitboard b2 = b1 & ofs.Rank8BB;
     while (b2)
     {
         sq = pop_1st_bit(&b2);
-        mlist[n++].move = make_promotion_move(sq - DELTA_NE, sq, QUEEN);
+        mlist[n++].move = make_promotion_move(sq - ofs.DELTA_NE, sq, QUEEN);
     }
 
     // Capturing non-promotions
-    b2 = b1 & ~Rank8BB;
+    b2 = b1 & ~ofs.Rank8BB;
     while (b2)
     {
         sq = pop_1st_bit(&b2);
-        mlist[n++].move = make_move(sq - DELTA_NE, sq);
+        mlist[n++].move = make_move(sq - ofs.DELTA_NE, sq);
     }
 
-    // Captures in the h1-a8 direction
-    b1 = (pawns << 7) & ~FileHBB & enemyPieces;
+    // Captures in the h1-a8 (h8-a1 for black) direction
+    b1 = (ofs.forward_left)(pawns) & ~FileHBB & enemyPieces;
 
     // Capturing promotions
-    b2 = b1 & Rank8BB;
+    b2 = b1 & ofs.Rank8BB;
     while (b2)
     {
         sq = pop_1st_bit(&b2);
-        mlist[n++].move = make_promotion_move(sq - DELTA_NW, sq, QUEEN);
+        mlist[n++].move = make_promotion_move(sq - ofs.DELTA_NW, sq, QUEEN);
     }
 
     // Capturing non-promotions
-    b2 = b1 & ~Rank8BB;
+    b2 = b1 & ~ofs.Rank8BB;
     while (b2)
     {
         sq = pop_1st_bit(&b2);
-        mlist[n++].move = make_move(sq - DELTA_NW, sq);
+        mlist[n++].move = make_move(sq - ofs.DELTA_NW, sq);
     }
 
     // Non-capturing promotions
-    b1 = (pawns << 8) & pos.empty_squares() & Rank8BB;
+    b1 = (ofs.forward)(pawns) & pos.empty_squares() & Rank8BB;
     while (b1)
     {
         sq = pop_1st_bit(&b1);
-        mlist[n++].move = make_promotion_move(sq - DELTA_N, sq, QUEEN);
+        mlist[n++].move = make_promotion_move(sq - ofs.DELTA_N, sq, QUEEN);
     }
 
     // En passant captures
     if (pos.ep_square() != SQ_NONE)
     {
-        assert(square_rank(pos.ep_square()) == RANK_6);
-        b1 = pawns & pos.black_pawn_attacks(pos.ep_square());
+        assert(ofs.us != WHITE || square_rank(pos.ep_square()) == RANK_6);
+        assert(ofs.us != BLACK || square_rank(pos.ep_square()) == RANK_3);
+
+        b1 = pawns & pos.pawn_attacks(ofs.them, pos.ep_square());
         assert(b1 != EmptyBoardBB);
+
         while (b1)
         {
             sq = pop_1st_bit(&b1);
@@ -773,176 +696,59 @@ namespace {
   }
 
 
-  int generate_black_pawn_captures(const Position &pos, MoveStack *mlist) {
+  int generate_pawn_noncaptures(const PawnOffsets& ofs, const Position& pos, MoveStack* mlist) {
 
-    Bitboard pawns = pos.pawns(BLACK);
-    Bitboard enemyPieces = pos.pieces_of_color(WHITE);
+    Bitboard pawns = pos.pawns(ofs.us);
+    Bitboard enemyPieces = pos.pieces_of_color(ofs.them);
+    Bitboard emptySquares = pos.empty_squares();
+    Bitboard b1, b2;
     Square sq;
     int n = 0;
 
-    // Captures in the a8-h1 direction
-    Bitboard b1 = (pawns >> 7) & ~FileABB & enemyPieces;
-
-    // Capturing promotions
-    Bitboard b2 = b1 & Rank1BB;
-    while (b2)
+    // Underpromotion captures in the a1-h8 (a8-h1 for black) direction
+    b1 = ofs.forward_right(pawns) & ~FileABB & enemyPieces & ofs.Rank8BB;
+    while (b1)
     {
-        sq = pop_1st_bit(&b2);
-        mlist[n++].move = make_promotion_move(sq - DELTA_SE, sq, QUEEN);
+        sq = pop_1st_bit(&b1);
+        mlist[n++].move = make_promotion_move(sq - ofs.DELTA_NE, sq, ROOK);
+        mlist[n++].move = make_promotion_move(sq - ofs.DELTA_NE, sq, BISHOP);
+        mlist[n++].move = make_promotion_move(sq - ofs.DELTA_NE, sq, KNIGHT);
     }
 
-    // Capturing non-promotions
-    b2 = b1 & ~Rank1BB;
-    while (b2)
+    // Underpromotion captures in the h1-a8 (h8-a1 for black) direction
+    b1 = ofs.forward_left(pawns) & ~FileHBB & enemyPieces & ofs.Rank8BB;
+    while (b1)
     {
-        sq = pop_1st_bit(&b2);
-        mlist[n++].move = make_move(sq - DELTA_SE, sq);
+        sq = pop_1st_bit(&b1);
+        mlist[n++].move = make_promotion_move(sq - ofs.DELTA_NW, sq, ROOK);
+        mlist[n++].move = make_promotion_move(sq - ofs.DELTA_NW, sq, BISHOP);
+        mlist[n++].move = make_promotion_move(sq - ofs.DELTA_NW, sq, KNIGHT);
     }
 
-    // Captures in the h8-a1 direction
-    b1 = (pawns >> 9) & ~FileHBB & enemyPieces;
-
-    // Capturing promotions
-    b2 = b1 & Rank1BB;
+    // Single pawn pushes
+    b1 = ofs.forward(pawns) & emptySquares;
+    b2 = b1 & ofs.Rank8BB;
     while (b2)
     {
-        sq = pop_1st_bit(&b2);
-        mlist[n++].move = make_promotion_move(sq - DELTA_SW, sq, QUEEN);
+      sq = pop_1st_bit(&b2);
+      mlist[n++].move = make_promotion_move(sq - ofs.DELTA_N, sq, ROOK);
+      mlist[n++].move = make_promotion_move(sq - ofs.DELTA_N, sq, BISHOP);
+      mlist[n++].move = make_promotion_move(sq - ofs.DELTA_N, sq, KNIGHT);
     }
-
-    // Capturing Non-promotions
-    b2 = b1 & ~Rank1BB;
+    b2 = b1 & ~ofs.Rank8BB;
     while (b2)
     {
         sq = pop_1st_bit(&b2);
-        mlist[n++].move = make_move(sq - DELTA_SW, sq);
-    }
-
-    // Non-capturing promotions
-    b1 = (pawns >> 8) & pos.empty_squares() & Rank1BB;
-    while (b1)
-    {
-        sq = pop_1st_bit(&b1);
-        mlist[n++].move = make_promotion_move(sq - DELTA_S, sq, QUEEN);
+        mlist[n++].move = make_move(sq - ofs.DELTA_N, sq);
     }
 
-    // En passant captures
-    if (pos.ep_square() != SQ_NONE)
+    // Double pawn pushes
+    b2 = (ofs.forward(b1 & ofs.Rank3BB)) & emptySquares;
+    while (b2)
     {
-        assert(square_rank(pos.ep_square()) == RANK_3);
-        b1 = pawns & pos.white_pawn_attacks(pos.ep_square());
-        assert(b1 != EmptyBoardBB);
-        while (b1)
-        {
-            sq = pop_1st_bit(&b1);
-            mlist[n++].move = make_ep_move(sq, pos.ep_square());
-        }
-    }
-    return n;
-  }
-
-
-  int generate_white_pawn_noncaptures(const Position &pos, MoveStack *mlist) {
-
-    Bitboard pawns = pos.pawns(WHITE);
-    Bitboard enemyPieces = pos.pieces_of_color(BLACK);
-    Bitboard emptySquares = pos.empty_squares();
-    Bitboard b1, b2;
-    Square sq;
-    int n = 0;
-
-    // Underpromotion captures in the a1-h8 direction:
-    b1 = (pawns << 9) & ~FileABB & enemyPieces & Rank8BB;
-    while(b1) {
-      sq = pop_1st_bit(&b1);
-      mlist[n++].move = make_promotion_move(sq - DELTA_NE, sq, ROOK);
-      mlist[n++].move = make_promotion_move(sq - DELTA_NE, sq, BISHOP);
-      mlist[n++].move = make_promotion_move(sq - DELTA_NE, sq, KNIGHT);
-    }
-
-    // Underpromotion captures in the h1-a8 direction:
-    b1 = (pawns << 7) & ~FileHBB & enemyPieces & Rank8BB;
-    while(b1) {
-      sq = pop_1st_bit(&b1);
-      mlist[n++].move = make_promotion_move(sq - DELTA_NW, sq, ROOK);
-      mlist[n++].move = make_promotion_move(sq - DELTA_NW, sq, BISHOP);
-      mlist[n++].move = make_promotion_move(sq - DELTA_NW, sq, KNIGHT);
-    }
-
-    // Single pawn pushes:
-    b1 = (pawns << 8) & emptySquares;
-    b2 = b1 & Rank8BB;
-    while(b2) {
-      sq = pop_1st_bit(&b2);
-      mlist[n++].move = make_promotion_move(sq - DELTA_N, sq, ROOK);
-      mlist[n++].move = make_promotion_move(sq - DELTA_N, sq, BISHOP);
-      mlist[n++].move = make_promotion_move(sq - DELTA_N, sq, KNIGHT);
-    }
-    b2 = b1 & ~Rank8BB;
-    while(b2) {
-      sq = pop_1st_bit(&b2);
-      mlist[n++].move = make_move(sq - DELTA_N, sq);
-    }
-
-    // Double pawn pushes:
-    b2 = ((b1 & Rank3BB) << 8) & emptySquares;
-    while(b2) {
-      sq = pop_1st_bit(&b2);
-      mlist[n++].move = make_move(sq - DELTA_N - DELTA_N, sq);
-    }
-
-    return n;
-  }
-
-
-  int generate_black_pawn_noncaptures(const Position &pos, MoveStack *mlist) {
-    Bitboard pawns = pos.pawns(BLACK);
-    Bitboard enemyPieces = pos.pieces_of_color(WHITE);
-    Bitboard emptySquares = pos.empty_squares();
-    Bitboard b1, b2;
-    Square sq;
-    int n = 0;
-
-    // Underpromotion captures in the a8-h1 direction:
-    b1 = (pawns >> 7) & ~FileABB & enemyPieces & Rank1BB;
-    while(b1) {
-      sq = pop_1st_bit(&b1);
-      mlist[n++].move = make_promotion_move(sq - DELTA_SE, sq, ROOK);
-      mlist[n++].move = make_promotion_move(sq - DELTA_SE, sq, BISHOP);
-      mlist[n++].move = make_promotion_move(sq - DELTA_SE, sq, KNIGHT);
-    }
-
-    // Underpromotion captures in the h8-a1 direction:
-    b1 = (pawns >> 9) & ~FileHBB & enemyPieces & Rank1BB;
-    while(b1) {
-      sq = pop_1st_bit(&b1);
-      mlist[n++].move = make_promotion_move(sq - DELTA_SW, sq, ROOK);
-      mlist[n++].move = make_promotion_move(sq - DELTA_SW, sq, BISHOP);
-      mlist[n++].move = make_promotion_move(sq - DELTA_SW, sq, KNIGHT);
-    }
-
-    // Single pawn pushes:
-    b1 = (pawns >> 8) & emptySquares;
-    b2 = b1 & Rank1BB;
-    while(b2) {
-      sq = pop_1st_bit(&b2);
-      mlist[n++].move = make_promotion_move(sq - DELTA_S, sq, ROOK);
-      mlist[n++].move = make_promotion_move(sq - DELTA_S, sq, BISHOP);
-      mlist[n++].move = make_promotion_move(sq - DELTA_S, sq, KNIGHT);
-    }
-    b2 = b1 & ~Rank1BB;
-    while(b2) {
-      sq = pop_1st_bit(&b2);
-      mlist[n++].move = make_move(sq - DELTA_S, sq);
-    }
-    
-    // Double pawn pushes:
-    b2 = ((b1 & Rank6BB) >> 8) & emptySquares;
-    while(b2) {
       sq = pop_1st_bit(&b2);
-      mlist[n++].move = make_move(sq - DELTA_S - DELTA_S, sq);
+      mlist[n++].move = make_move(sq - ofs.DELTA_N - ofs.DELTA_N, sq);
     }
-
     return n;
   }
 
@@ -970,68 +776,74 @@ namespace {
 
 
   int generate_castle_moves(const Position &pos, MoveStack *mlist, Color us) {
+
     int n = 0;
 
-    if(pos.can_castle(us)) {
-      Color them = opposite_color(us);
-      Square ksq = pos.king_square(us);
-      assert(pos.piece_on(ksq) == king_of_color(us));
-      
-      if(pos.can_castle_kingside(us)) {
-        Square rsq = pos.initial_kr_square(us);
-        Square g1 = relative_square(us, SQ_G1);
-        Square f1 = relative_square(us, SQ_F1);
-        Square s;
-        bool illegal = false;
+    if (pos.can_castle(us))
+    {
+        Color them = opposite_color(us);
+        Square ksq = pos.king_square(us);        
 
-        assert(pos.piece_on(rsq) == rook_of_color(us));
+        assert(pos.piece_on(ksq) == king_of_color(us));
 
-        for(s = Min(ksq, g1); s <= Max(ksq, g1); s++)
-          if((s != ksq && s != rsq && pos.square_is_occupied(s))
-             || pos.square_is_attacked(s, them))
-            illegal = true;
-        for(s = Min(rsq, f1); s <= Max(rsq, f1); s++)
-          if(s != ksq && s != rsq && pos.square_is_occupied(s))
-            illegal = true;
+        if (pos.can_castle_kingside(us))
+        {
+            Square rsq = pos.initial_kr_square(us);
+            Square g1 = relative_square(us, SQ_G1);
+            Square f1 = relative_square(us, SQ_F1);
+            Square s;
+            bool illegal = false;
 
-        if(!illegal)
-          mlist[n++].move = make_castle_move(ksq, rsq);
-      }
+            assert(pos.piece_on(rsq) == rook_of_color(us));
 
-      if(pos.can_castle_queenside(us)) {
-        Square rsq = pos.initial_qr_square(us);
-        Square c1 = relative_square(us, SQ_C1);
-        Square d1 = relative_square(us, SQ_D1);
-        Square s;
-        bool illegal = false;
+            for (s = Min(ksq, g1); s <= Max(ksq, g1); s++)
+                if (  (s != ksq && s != rsq && pos.square_is_occupied(s))
+                    || pos.square_is_attacked(s, them))
+                    illegal = true;
 
-        assert(pos.piece_on(rsq) == rook_of_color(us));
+            for (s = Min(rsq, f1); s <= Max(rsq, f1); s++)
+                if (s != ksq && s != rsq && pos.square_is_occupied(s))
+                    illegal = true;
 
-        for(s = Min(ksq, c1); s <= Max(ksq, c1); s++)
-          if((s != ksq && s != rsq && pos.square_is_occupied(s))
-             || pos.square_is_attacked(s, them))
-            illegal = true;
-        for(s = Min(rsq, d1); s <= Max(rsq, d1); s++)
-          if(s != ksq && s != rsq && pos.square_is_occupied(s))
+            if (!illegal)
+                mlist[n++].move = make_castle_move(ksq, rsq);
+      }
+
+      if (pos.can_castle_queenside(us))
+      {
+          Square rsq = pos.initial_qr_square(us);
+          Square c1 = relative_square(us, SQ_C1);
+          Square d1 = relative_square(us, SQ_D1);
+          Square s;
+          bool illegal = false;        
+
+          assert(pos.piece_on(rsq) == rook_of_color(us));
+
+          for (s = Min(ksq, c1); s <= Max(ksq, c1); s++)
+              if (  (s != ksq && s != rsq && pos.square_is_occupied(s))
+                  || pos.square_is_attacked(s, them))
+                  illegal = true;
+
+          for (s = Min(rsq, d1); s <= Max(rsq, d1); s++)
+              if (s != ksq && s != rsq && pos.square_is_occupied(s))
+                  illegal = true;
+
+        if (   square_file(rsq) == FILE_B
+            && (   pos.piece_on(relative_square(us, SQ_A1)) == rook_of_color(them)
+                || pos.piece_on(relative_square(us, SQ_A1)) == queen_of_color(them)))
             illegal = true;
-        if(square_file(rsq) == FILE_B &&
-           (pos.piece_on(relative_square(us, SQ_A1)) == rook_of_color(them) ||
-            pos.piece_on(relative_square(us, SQ_A1)) == queen_of_color(them)))
-           illegal = true;
                          
-        if(!illegal)
-          mlist[n++].move = make_castle_move(ksq, rsq);
+        if (!illegal)
+            mlist[n++].move = make_castle_move(ksq, rsq);
       }
     }
-
     return n;
   }
 
   int generate_piece_checks(PieceType pce, const Position& pos, Bitboard target,
-                          Bitboard dc, Square ksq, MoveStack* mlist) {
+                          Bitboard dc, Square ksq, MoveStack* mlist, int n) {
 
     const Piece_attacks_fn mem_fn = piece_attacks_fn[pce];
-    int n = 0;
 
     // Discovered checks
     Bitboard b = target & dc;
@@ -1061,4 +873,54 @@ namespace {
     }
     return n;
   }
+
+  int generate_pawn_checks(const PawnOffsets& ofs, const Position& pos, Bitboard dc, Square ksq, MoveStack* mlist, int n)
+  {
+    // Pawn moves which give discovered check. This is possible only if the 
+    // pawn is not on the same file as the enemy king, because we don't 
+    // generate captures.
+    Bitboard empty = pos.empty_squares();
+
+    // Find all friendly pawns not on the enemy king's file
+    Bitboard b1 = pos.pawns(pos.side_to_move()) & ~file_bb(ksq), b2, b3;
+
+    // Discovered checks, single pawn pushes
+    b2 = b3 = (ofs.forward)(b1 & dc) & ~ofs.Rank8BB & empty;
+    while (b3)
+    {
+        Square to = pop_1st_bit(&b3);
+        mlist[n++].move = make_move(to - ofs.DELTA_N, to);
+    }
+
+    // Discovered checks, double pawn pushes
+    b3 = (ofs.forward)(b2 & ofs.Rank3BB) & empty;
+    while (b3)
+    {
+        Square to = pop_1st_bit(&b3);
+        mlist[n++].move = make_move(to - ofs.DELTA_N - ofs.DELTA_N, to);
+    }
+
+    // Direct checks. These are possible only for pawns on neighboring files
+    // of the enemy king
+
+    b1 &= (~dc & neighboring_files_bb(ksq)); // FIXME why ~dc ??
+
+    // Direct checks, single pawn pushes
+    b2 = (ofs.forward)(b1) & empty;
+    b3 = b2 & pos.pawn_attacks(ofs.them, ksq);
+    while (b3)
+    {
+        Square to = pop_1st_bit(&b3);
+        mlist[n++].move = make_move(to - ofs.DELTA_N, to);
+    }
+
+    // Direct checks, double pawn pushes
+    b3 = (ofs.forward)(b2 & ofs.Rank3BB) & empty & pos.pawn_attacks(ofs.them, ksq);
+    while (b3)
+    {
+        Square to = pop_1st_bit(&b3);
+        mlist[n++].move = make_move(to - ofs.DELTA_N - ofs.DELTA_N, to);
+    }
+    return n;
+  }
 }