From c34b4c1b036058b2906556850cc4ded6ececcf89 Mon Sep 17 00:00:00 2001
From: Aargh Rai <aargh.rai+git@gmail.com>
Date: Thu, 16 Jul 2026 23:03:28 +0530
Subject: fixed pawn gen, onto the next perf

---
 src/engine/moves/knight.c |  6 +++---
 src/engine/moves/pawn.c   | 16 ++++++++++++----
 2 files changed, 15 insertions(+), 7 deletions(-)

(limited to 'src/engine/moves')

diff --git a/src/engine/moves/knight.c b/src/engine/moves/knight.c
index 64e44ed..4aca3ac 100644
--- a/src/engine/moves/knight.c
+++ b/src/engine/moves/knight.c
@@ -68,9 +68,9 @@ bitboard_t knight_moves[64] = {
   1128098930098176ULL,
   2257297371824128ULL,
   4796069720358912ULL,
-  4796069720358912ULL >> 1,
-  4796069720358912ULL >> 2,
-  4796069720358912ULL >> 3,
+  4796069720358912ULL << 1,
+  4796069720358912ULL << 2,
+  4796069720358912ULL << 3,
   4679521487814656ULL,
   9077567998918656ULL,
 };
diff --git a/src/engine/moves/pawn.c b/src/engine/moves/pawn.c
index 66b1d06..bc97fb7 100644
--- a/src/engine/moves/pawn.c
+++ b/src/engine/moves/pawn.c
@@ -34,6 +34,12 @@ bitboard_t get_black_pawn_forwardmoves(moves_t* moves, position_t position) {
   return x;
 }
 
+bool pawn_in_range(int to, int next_from, int ub_escape, int turn) {
+  if (next_from == ub_escape) return false;
+  if (turn == WHITE_TURN) return to > next_from && to - next_from <= 16;
+  return to < next_from && next_from - to <= 16;
+}
+
 void get_pawn_moves(moves_t* moves, position_t position) {
   assert_valid_position(position);
 
@@ -65,20 +71,23 @@ void get_pawn_moves(moves_t* moves, position_t position) {
     bitboard_t item = file_masks[i] & forward_moves;
     bitboard_t pawns = file_masks[i] & friendly_pawns;
 
+    int UB_ESCAPE = position.turn == WHITE_TURN ? 64 : -1;
+
     int from = __builtin_ctzll(pawns);
     pawns &= (pawns - 1);
     int next_from = __builtin_ctzll(pawns);
-    if (pawns == 0) next_from = 64; // to work around UB
+    if (pawns == 0) next_from = UB_ESCAPE;
     
     while (item) {
       int to = __builtin_ctzll(item);
-      if (to > next_from) {
+      if (pawn_in_range(to, next_from, UB_ESCAPE, position.turn)) {
         from = next_from;
         pawns &= (pawns - 1);
         next_from = __builtin_ctzll(pawns);
-        if (pawns == 0) next_from = 64;
+        if (pawns == 0) next_from = UB_ESCAPE;
       }
       item &= (item - 1);
+
       if (to >= 56 || to <= 7) {
         add_promote_moves(0);
       } else add_move(moves, from, to);
@@ -128,7 +137,6 @@ void get_pawn_moves(moves_t* moves, position_t position) {
     }
   }
 
-
   bitboard_t ATTACK_MASK;
   int shift;
   if (position.turn == WHITE_TURN) {
-- 
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