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movegen: cleanup + change casling/king moves handling

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This commit is contained in:
Bruno Raoult
2024-06-24 09:00:24 +02:00
parent cfa8b42077
commit d1cc7a8066
1 changed files with 34 additions and 36 deletions
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70
src/move-gen.c
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@@ -26,7 +26,6 @@
#include "attack.h" #include "attack.h"
#include "move-gen.h" #include "move-gen.h"
/** /**
* pseudo_is_legal() - check if a move is legal. * pseudo_is_legal() - check if a move is legal.
* @pos: position * @pos: position
@@ -36,13 +35,18 @@
*/ */
bool pseudo_is_legal(const pos_t *pos, const move_t move) bool pseudo_is_legal(const pos_t *pos, const move_t move)
{ {
color_t us = pos->turn, them = OPPONENT(us); color_t us = pos->turn;
square_t from = move_from(move), to = move_to(move); color_t them = OPPONENT(us);
square_t king = pos->king[us]; square_t from = move_from(move);
square_t to = move_to(move);
square_t kingsq = pos->king[us];
square_t ep = pos->en_passant;
bitboard_t kingbb = pos->bb[us][KING]; bitboard_t kingbb = pos->bb[us][KING];
bitboard_t occ = pos_occ(pos); bitboard_t occ = pos_occ(pos);
u64 pinned = BIT(from) & pos->blockers; u64 pinned = BIT(from) & pos->blockers;
u64 checkers = pos->checkers; u64 checkers = pos->checkers;
bug_on(pos->board[from] == NO_PIECE || COLOR(pos->board[from]) != us);
/* (1) - Castling & King /* (1) - Castling & King
* For castling, we need to check intermediate squares attacks only. * For castling, we need to check intermediate squares attacks only.
@@ -50,60 +54,52 @@ bool pseudo_is_legal(const pos_t *pos, const move_t move)
* king from occupation bitboard (to catch king moving away from checker * king from occupation bitboard (to catch king moving away from checker
* on same line) ! * on same line) !
*/ */
if (unlikely(from == king)) { if (is_castle(move)) {
if (unlikely(is_castle(move))) { int dir = to > from? 1: -1;
square_t dir = to > from? 1: -1; if (sq_is_attacked(pos, occ, from + dir, them))
if (sq_is_attacked(pos, occ, from + dir, them)) return false;
return false; }
} if (from == kingsq) {
return !sq_is_attacked(pos, occ ^ kingbb, to, them); return !sq_is_attacked(pos, occ ^ kingbb, to, them);
} }
/* (2) - King is in check /* (2) - King is in check
* Double-check is already handled in (1), as only K moves were generated * Double-check is already handled in (1), as only K moves were generated
* by pseudo legal move generator. * by pseudo legal move generator.
* Here, allowed dest squares are only on King-checker line, or on checker * Special cases (illegal):
* square. * - e.p., if the grabbed pawn is *not* giving check
* attacker. * - piece is pinned
* Special cases:
* e.p., legal if the grabbed pawn is giving check
* pinned piece: always illegal
*/ */
if (checkers) { if (checkers) {
if (pinned) if (pinned)
return false; return false;
if (bb_multiple(checkers))
return false;
square_t checker = ctz64(checkers);
if (is_enpassant(move)) { if (is_enpassant(move)) {
return pos->en_passant + sq_up(them) == checker; return ep + sq_up(them) == ctz64(checkers);
} }
return true; return true;
//bitboard_t between = bb_between[king][checker] | pos->checkers;
//return mask(to) & between;
} }
/* (3) - pinned pieces /* (3) - pinned pieces
* We verify here that pinned piece P stays on line King-P. * We verify here that pinned piece P stays on line between K & dest square.
*/ */
if (BIT(from) & pos->blockers) { if (pinned) {
return bb_line[from][king] & BIT(to); /* is to on pinner line ? */ return bb_line[from][kingsq] & BIT(to); /* is to on pinner line ? */
} }
/* (4) - En-passant /* (4) - En-passant
* pinned pieces are handled in pinned section. * pinned piece is already handled in (3).
* One case not handled anywhere else: when the two "disappearing" pawns * One case not handled anywhere else: when the two "disappearing" pawns
* would discover a R/Q horizontal check. * would discover a R/Q horizontal check.
* Note: grabbed pawn *cannot* discover a check (impossible position).
*/ */
if (unlikely(is_enpassant(move))) { if (is_enpassant(move)) {
bitboard_t rank5 = bb_rel_rank(RANK_5, us); bitboard_t rank5 = bb_rel_rank(RANK_5, us);
if (unlikely((pos->bb[us][KING] & rank5))) { if (kingbb & rank5) {
bitboard_t exclude = BIT(pos->en_passant - sq_up(us)) | BIT(from); bitboard_t exclude = BIT(ep + sq_up(them)) | BIT(from);
bitboard_t rooks = (pos->bb[them][ROOK] | pos->bb[them][QUEEN]) & rank5; bitboard_t rooks = (pos->bb[them][ROOK] | pos->bb[them][QUEEN]) & rank5;
if (hyperbola_rank_moves(occ ^ exclude, king) & rooks) return !(hyperbola_rank_moves(occ ^ exclude, kingsq) & rooks);
return false;
} }
} }
return true; return true;
@@ -349,12 +345,12 @@ movelist_t *pos_gen_pseudo(pos_t *pos, movelist_t *movelist)
bitboard_t dest_squares = ~my_pieces; bitboard_t dest_squares = ~my_pieces;
bitboard_t occ = my_pieces | enemy_pieces; bitboard_t occ = my_pieces | enemy_pieces;
bitboard_t empty = ~occ; bitboard_t empty = ~occ;
move_t *moves = movelist->move;
square_t king = pos->king[us];
bitboard_t from_bb, to_bb; bitboard_t from_bb, to_bb;
bitboard_t tmp_bb; bitboard_t tmp_bb;
move_t *moves = movelist->move;
square_t from, to; square_t from, to;
square_t king = pos->king[us];
/* king - MUST BE FIRST */ /* king - MUST BE FIRST */
to_bb = bb_king_moves(dest_squares, king); to_bb = bb_king_moves(dest_squares, king);
@@ -379,6 +375,8 @@ movelist_t *pos_gen_pseudo(pos_t *pos, movelist_t *movelist)
* To square attack check will be done in gen_is_legal. * To square attack check will be done in gen_is_legal.
*/ */
if (can_oo(pos->castle, us)) { if (can_oo(pos->castle, us)) {
/* CHANGE HERE, either with bitmask >> or direct sq check */
bitboard_t occmask = rel_rank1 & (FILE_Fbb | FILE_Gbb); bitboard_t occmask = rel_rank1 & (FILE_Fbb | FILE_Gbb);
if (!(occ & occmask)) { if (!(occ & occmask)) {
*moves++ = move_make_flags(king, king + 2, M_CASTLE_K); *moves++ = move_make_flags(king, king + 2, M_CASTLE_K);