From 34b75f1575698759ab180da369be5e65364a9d1e Mon Sep 17 00:00:00 2001
From: pb00067 <guenther.demetz@wuerth-phoenix.com>
Date: Tue, 3 Jun 2025 13:52:17 +0200
Subject: [PATCH] Restore integrity of MovePicker::can_move_king_or_pawn

PR6005 broken by PR6071

passed STC non regression
https://tests.stockfishchess.org/tests/view/6839791f6ec7634154f9d312
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 31776 W: 8353 L: 8130 D: 15293
Ptnml(0-2): 74, 3566, 8382, 3795, 71

passed LTC non-regression
https://tests.stockfishchess.org/tests/view/6839c87a6ec7634154f9d367
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 120756 W: 31015 L: 30899 D: 58842
Ptnml(0-2): 50, 12732, 34703, 12838, 55

closes https://github.com/official-stockfish/Stockfish/pull/6119

Bench: 1945300
---
 src/movepick.cpp | 26 +++++++++++---------------
 src/movepick.h   |  2 +-
 2 files changed, 12 insertions(+), 16 deletions(-)

diff --git a/src/movepick.cpp b/src/movepick.cpp
index d2764fa8..3e7c1016 100644
--- a/src/movepick.cpp
+++ b/src/movepick.cpp
@@ -56,6 +56,7 @@ enum Stages {
     QCAPTURE
 };
 
+
 // Sort moves in descending order up to and including a given limit.
 // The order of moves smaller than the limit is left unspecified.
 void partial_insertion_sort(ExtMove* begin, ExtMove* end, int limit) {
@@ -207,6 +208,7 @@ Move MovePicker::select(Pred filter) {
 // picking the move with the highest score from a list of generated moves.
 Move MovePicker::next_move() {
 
+    constexpr int goodQuietThreshold = -14000;
 top:
     switch (stage)
     {
@@ -222,7 +224,7 @@ top:
     case PROBCUT_INIT :
     case QCAPTURE_INIT :
         cur = endBadCaptures = moves;
-        endCur               = generate<CAPTURES>(pos, cur);
+        endCur = endCaptures = generate<CAPTURES>(pos, cur);
 
         score<CAPTURES>();
         partial_insertion_sort(cur, endCur, std::numeric_limits<int>::min());
@@ -244,8 +246,7 @@ top:
     case QUIET_INIT :
         if (!skipQuiets)
         {
-            cur = endBadQuiets = endBadCaptures;
-            endCur             = generate<QUIETS>(pos, cur);
+            endCur = endGenerated = generate<QUIETS>(pos, cur);
 
             score<QUIETS>();
             partial_insertion_sort(cur, endCur, -3560 * depth);
@@ -255,12 +256,7 @@ top:
         [[fallthrough]];
 
     case GOOD_QUIET :
-        if (!skipQuiets && select([&]() {
-                if (cur->value > -14000)
-                    return true;
-                *endBadQuiets++ = *cur;
-                return false;
-            }))
+        if (!skipQuiets && select([&]() { return cur->value > goodQuietThreshold; }))
             return *(cur - 1);
 
         // Prepare the pointers to loop over the bad captures
@@ -274,22 +270,22 @@ top:
         if (select([]() { return true; }))
             return *(cur - 1);
 
-        // Prepare the pointers to loop over the bad quiets
-        cur    = endBadCaptures;
-        endCur = endBadQuiets;
+        // Prepare the pointers to loop over quiets again
+        cur    = endCaptures;
+        endCur = endGenerated;
 
         ++stage;
         [[fallthrough]];
 
     case BAD_QUIET :
         if (!skipQuiets)
-            return select([]() { return true; });
+            return select([&]() { return cur->value <= goodQuietThreshold; });
 
         return Move::none();
 
     case EVASION_INIT :
         cur    = moves;
-        endCur = generate<EVASIONS>(pos, cur);
+        endCur = endGenerated = generate<EVASIONS>(pos, cur);
 
         score<EVASIONS>();
         partial_insertion_sort(cur, endCur, std::numeric_limits<int>::min());
@@ -315,7 +311,7 @@ bool MovePicker::can_move_king_or_pawn() const {
     // SEE negative captures shouldn't be returned in GOOD_CAPTURE stage
     assert(stage > GOOD_CAPTURE && stage != EVASION_INIT);
 
-    for (const ExtMove* m = moves; m < endCur; ++m)
+    for (const ExtMove* m = moves; m < endGenerated; ++m)
     {
         PieceType movedPieceType = type_of(pos.moved_piece(*m));
         if ((movedPieceType == PAWN || movedPieceType == KING) && pos.legal(*m))
diff --git a/src/movepick.h b/src/movepick.h
index b6784fb7..bf0c96c7 100644
--- a/src/movepick.h
+++ b/src/movepick.h
@@ -67,7 +67,7 @@ class MovePicker {
     const PieceToHistory**       continuationHistory;
     const PawnHistory*           pawnHistory;
     Move                         ttMove;
-    ExtMove *                    cur, *endCur, *endBadCaptures, *endBadQuiets;
+    ExtMove *                    cur, *endCur, *endBadCaptures, *endCaptures, *endGenerated;
     int                          stage;
     int                          threshold;
     Depth                        depth;