Make bitboard move generation unconditional; delete the mailbox fallback

All GENERATE_*_BITBOARD/EXPOSESCHECK_BITBOARD/ISATTACKED_BITBOARD/
UNBLOCKED_BITBOARD flags were already default-on (ifndef
DISABLE_BITBOARD_MOVEGEN); this removes that opt-out entirely (GNUmakefile)
and deletes the mailbox-era code the flags used to toggle between, since
there's no longer a build configuration that still needs it:

- generate.c: the mailbox per-piece generators and escape-generators
  (GenerateKnight/GenerateWhiteKnight/GenerateBishop/GenerateRook/
  GenerateQueen/GenerateBlackKing/GenerateWhiteKing/GenerateWhitePawn/
  GenerateBlackPawn and their SaveMe* escape-generator counterparts),
  _FindUnblockedSquares and its DEBUG-build cross-check inside
  _FindUnblockedSquaresBB, and the dispatch-table #if/#else pairs that
  chose between mailbox and bitboard functions (now unconditionally
  bitboard). WouldGiveCheck simplified to its UNBLOCKED_BITBOARD-only
  body. g_iBDeltas/g_iRDeltas (orphaned once their only consumers were
  deleted) removed; g_iNDeltas (still used by data.c's InitMagic) moved
  there, next to its real consumer.
- movesup.c: mailbox FasterExposesCheck/ExposesCheck/ExposesCheckEp/
  IsAttacked/InCheck deleted; chess.h's three-way macro choice
  simplified to a direct #define onto the BB versions (ExposesCheckBB/
  IsAttackedBB/etc. are simply "the" implementation now).
- testsee.c/testgenerate.c: deleted the mailbox-vs-BB comparison/speed
  harnesses that only existed to validate code just removed
  (TestIsAttackedBB, TestGenerateKnightSpeed/KingSpeed/RookSpeed/
  BishopSpeed/QueenSpeed, TestFindUnblockedSquaresSpeed's mailbox arm).
  TestGetAttacks and the _GenerateAllMoves-vs-_GenerateAllMovesBB
  dispatch-overhead benchmark are unaffected -- GetAttacks' mailbox/asm
  predecessors were already retired independently, and that pair
  compares two still-live BB-only dispatch strategies, not mailbox vs
  BB.

Verified: clean release build and a clean DEBUG=1 TEST=1 self-test run
(move generation, perft-style legal-move checks, SAN/ICS parsing,
search smoke test) with no assertion failures.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

1 files changed, 10 insertions, 122 deletions

diff --git a/src/chess.h b/src/chess.h
index 85b4bd7..2942f0a 100755
--- a/src/chess.h
+++ b/src/chess.h
@@ -950,17 +950,12 @@ MOVE_STACK;
 #define GENERATE_DONT_SCORE            (5)
 
 // generate.c's _GenerateCapturesAndPromotions (GENERATE_CAPTURES_PROMS's
-// direct, non-filtered generator) exists only when every piece type is
-// on its bitboard generator -- see that function's block comment in
-// generate.c. Declared here, not in generate.c, so every translation
-// unit that needs to know whether it exists (main.c's test-registration
-// list, testgenerate.c's own tests) sees the same answer generate.c's
-// GenerateMoves dispatch does.
-#if defined(GENERATE_KNIGHT_BITBOARD) && defined(GENERATE_BISHOP_BITBOARD) && \
-    defined(GENERATE_ROOK_BITBOARD) && defined(GENERATE_QUEEN_BITBOARD) && \
-    defined(GENERATE_KING_BITBOARD) && defined(GENERATE_PAWN_BITBOARD)
+// direct, non-filtered generator) -- every piece type is always on its
+// bitboard generator now, so this is unconditional; kept as a named
+// macro (rather than inlined away) so main.c's test-registration list
+// and testgenerate.c's own tests keep one clearly-named thing to guard
+// on, matching generate.c's own #if there.
 #define CAPTURES_PROMS_BITBOARD_PATH 1
-#endif
 
 #ifdef TEST
 #define GENERATE_ALL_MOVES_CHECK_OK    (6)
@@ -3446,24 +3441,9 @@ DumpMove(ULONG u);
 #define MOVE_TO_INDEX(mv)  (((mv).uMove & 0xFFFF) + \
                             (0x10000 * GET_COLOR(mv.pMoved)))
 
-COOR
-FasterExposesCheck(POSITION *pos,
-                   COOR cRemove,
-                   COOR cLocation);
-
-COOR
-ExposesCheck(POSITION *pos,
-             COOR cRemove,
-             COOR cLocation);
-
-COOR
-ExposesCheckEp(POSITION *pos,
-               COOR cTest,
-               COOR cIgnore,
-               COOR cBlock,
-               COOR cKing);
-
-// board_representation/MOVEGEN_MIGRATION.md section 6b
+// board_representation/MOVEGEN_MIGRATION.md section 6b. The mailbox
+// originals (and the three-way #ifdef choice between them and these)
+// are retired -- these are simply the real implementations now.
 COOR
 FasterExposesCheckBB(POSITION *pos,
                      COOR cRemove,
@@ -3481,29 +3461,9 @@ ExposesCheckEpBB(POSITION *pos,
                  COOR cBlock,
                  COOR cKing);
 
-// Three-way choice matching GetAttacks's own pattern (MIGRATION.md
-// section 6): EXPOSESCHECK_BITBOARD defined -> the BB versions above;
-// else the mailbox versions declared right above this block.
-#if defined(EXPOSESCHECK_BITBOARD)
 #define ExposesCheck ExposesCheckBB
 #define FasterExposesCheck FasterExposesCheckBB
 #define ExposesCheckEp ExposesCheckEpBB
-#endif
-
-// Real mailbox declarations first, unconditionally, so the plain names
-// "IsAttacked"/"InCheck" are always genuinely declared -- the #define
-// below only affects *later* call sites in files that include this
-// header after this point, matching GetAttacks's own three-way-choice
-// pattern (chess.h, `GetAttacks` block) exactly. Declaring these after
-// the #define instead (an earlier mistake here, caught by testsee.c's
-// TestIsAttackedBB needing to call the real mailbox function by name)
-// would macro-substitute this very declaration too, leaving the real
-// name never actually declared anywhere.
-FLAG
-IsAttacked(COOR cTest, POSITION *pos, ULONG uSide);
-
-FLAG
-InCheck(POSITION *pos, ULONG uSide);
 
 FLAG
 IsAttackedBB(COOR cTest, POSITION *pos, ULONG uSide);
@@ -3511,13 +3471,8 @@ IsAttackedBB(COOR cTest, POSITION *pos, ULONG uSide);
 FLAG FORCEINLINE
 InCheckBB(POSITION *pos, ULONG uSide);
 
-// ISATTACKED_BITBOARD defined -> the BB versions above resolve plain
-// "IsAttacked"/"InCheck" call sites from here on; else the mailbox
-// versions declared just above stay live.
-#if defined(ISATTACKED_BITBOARD)
 #define IsAttacked IsAttackedBB
 #define InCheck InCheckBB
-#endif
 
 FLAG
 SanityCheckMove(POSITION *pos, MOVE mv);
@@ -3675,8 +3630,6 @@ TestMakeUnmakeMove(void);
 
 extern const int g_iQKDeltas[9];
 extern const int g_iNDeltas[9];
-extern const int g_iBDeltas[5];
-extern const int g_iRDeltas[5];
 
 void
 GenerateMoves(SEARCHER_THREAD_CONTEXT *ctx,
@@ -3703,45 +3656,23 @@ _RookAttacksBB(COOR c, BITBOARD bbOccupied);
 BITBOARD
 _BishopAttacksBB(COOR c, BITBOARD bbOccupied);
 
-// generate.c's bitboard replacement for _FindUnblockedSquares, exposed
-// non-static so testgenerate.c's correctness/speed harness can call it
-// directly regardless of whether UNBLOCKED_BITBOARD is defined for
-// this build.
+// generate.c's bitboard build of pStack->bbUnblocked -- the mailbox
+// original (and its DEBUG-build cross-check against this) is retired.
 void
 _FindUnblockedSquaresBB(MOVE_STACK *pStack,
                         POSITION *pos);
 
-// The mailbox original, exposed non-static (compiled whenever
-// !UNBLOCKED_BITBOARD, or under DEBUG/TEST for the cross-check and
-// the test harness above) under the same build conditions generate.c
-// itself uses -- see generate.c.
-#if !defined(UNBLOCKED_BITBOARD) || defined(DEBUG) || defined(TEST)
-void
-_FindUnblockedSquares(MOVE_STACK *pStack,
-                      POSITION *pos);
-#endif
-
 void
 _GenerateRookBB(MOVE_STACK *pStack,
                 POSITION *pos,
                 COOR cRook);
 
 void
-GenerateRook(MOVE_STACK *pStack,
-             POSITION *pos,
-             COOR cRook);
-
-void
 _GenerateBishopBB(MOVE_STACK *pStack,
                    POSITION *pos,
                    COOR cBishop);
 
 void
-GenerateBishop(MOVE_STACK *pStack,
-               POSITION *pos,
-               COOR cBishop);
-
-void
 _GenerateQueenBB(MOVE_STACK *pStack,
                  POSITION *pos,
                  COOR cQueen);
@@ -3802,40 +3733,15 @@ _SaveMeAllPawnMovesBB(MOVE_STACK *pStack,
                       BITBOARD bbTargetMask);
 
 void
-GenerateQueen(MOVE_STACK *pStack,
-              POSITION *pos,
-              COOR cQueen);
-
-void
 _GenerateKnightBB(MOVE_STACK *pStack,
                    POSITION *pos,
                    COOR cKnight);
 
 void
-GenerateKnight(MOVE_STACK *pStack,
-               POSITION *pos,
-               COOR cKnight);
-
-void
-GenerateWhiteKnight(MOVE_STACK *pStack,
-                    POSITION *pos,
-                    COOR cKnight);
-
-void
 _GenerateKingBB(MOVE_STACK *pStack,
                 POSITION *pos,
                 COOR cKing);
 
-void
-GenerateBlackKing(MOVE_STACK *pStack,
-                  POSITION *pos,
-                  COOR cKing);
-
-void
-GenerateWhiteKing(MOVE_STACK *pStack,
-                  POSITION *pos,
-                  COOR cKing);
-
 FLAG FORCEINLINE
 WouldGiveCheck(IN SEARCHER_THREAD_CONTEXT *ctx,
                IN MOVE mv);
@@ -3860,21 +3766,6 @@ void
 TestNnueAccumulator(void);
 
 void
-TestGenerateKnightSpeed(void);
-
-void
-TestGenerateKingSpeed(void);
-
-void
-TestGenerateRookSpeed(void);
-
-void
-TestGenerateBishopSpeed(void);
-
-void
-TestGenerateQueenSpeed(void);
-
-void
 TestGenerateAllMovesSpeed(void);
 
 void
@@ -4903,9 +4794,6 @@ void
 TestGetAttacks(void);
 
 void
-TestIsAttackedBB(void);
-
-void
 TestSeeFastSign(void);
 
 void