From a2038c1a011552c3d56d3b318780f7f5eadaf05d Mon Sep 17 00:00:00 2001
From: Jonathan <jonathan.mcdermid1@ucalgary.ca>
Date: Tue, 17 Jan 2023 21:30:50 -0700
Subject: [PATCH] apply if constexpr to additional instances

as a form of documentation, and a hint to the compiler.

closes https://github.com/official-stockfish/Stockfish/pull/4345

No functional change
---
 AUTHORS          |  1 +
 src/evaluate.cpp | 10 +++++-----
 src/movegen.cpp  | 16 ++++++++--------
 src/movepick.cpp |  2 +-
 4 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/AUTHORS b/AUTHORS
index 87fed7b8..42ba5930 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -101,6 +101,7 @@ Jerry Donald Watson (jerrydonaldwatson)
 jjoshua2
 Jonathan Calovski (Mysseno)
 Jonathan Buladas Dumale (SFisGOD)
+Jonathan McDermid (jonathanmcdermid)
 Joost VandeVondele (vondele)
 Jörg Oster (joergoster)
 Joseph Ellis (jhellis3)
diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 6db977a4..8683182c 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -388,10 +388,10 @@ namespace {
   template<Tracing T> template<Color Us, PieceType Pt>
   Score Evaluation<T>::pieces() {
 
-    constexpr Color     Them = ~Us;
-    constexpr Direction Down = -pawn_push(Us);
-    constexpr Bitboard OutpostRanks = (Us == WHITE ? Rank4BB | Rank5BB | Rank6BB
-                                                   : Rank5BB | Rank4BB | Rank3BB);
+    constexpr Color Them = ~Us;
+    [[maybe_unused]] constexpr Direction Down = -pawn_push(Us);
+    [[maybe_unused]] constexpr Bitboard OutpostRanks = (Us == WHITE ? Rank4BB | Rank5BB | Rank6BB
+                                                                    : Rank5BB | Rank4BB | Rank3BB);
     Bitboard b1 = pos.pieces(Us, Pt);
     Bitboard b, bb;
     Score score = SCORE_ZERO;
@@ -430,7 +430,7 @@ namespace {
         int mob = popcount(b & mobilityArea[Us]);
         mobility[Us] += MobilityBonus[Pt - 2][mob];
 
-        if (Pt == BISHOP || Pt == KNIGHT)
+        if constexpr (Pt == BISHOP || Pt == KNIGHT)
         {
             // Bonus if the piece is on an outpost square or can reach one
             // Bonus for knights (UncontestedOutpost) if few relevant targets
diff --git a/src/movegen.cpp b/src/movegen.cpp
index a960f863..47154164 100644
--- a/src/movegen.cpp
+++ b/src/movegen.cpp
@@ -26,12 +26,12 @@ namespace Stockfish {
 namespace {
 
   template<GenType Type, Direction D>
-  ExtMove* make_promotions(ExtMove* moveList, Square to) {
+  ExtMove* make_promotions(ExtMove* moveList, [[maybe_unused]] Square to) {
 
-    if (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
+    if constexpr (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
         *moveList++ = make<PROMOTION>(to - D, to, QUEEN);
 
-    if (Type == QUIETS || Type == EVASIONS || Type == NON_EVASIONS)
+    if constexpr (Type == QUIETS || Type == EVASIONS || Type == NON_EVASIONS)
     {
         *moveList++ = make<PROMOTION>(to - D, to, ROOK);
         *moveList++ = make<PROMOTION>(to - D, to, BISHOP);
@@ -60,18 +60,18 @@ namespace {
     Bitboard pawnsNotOn7 = pos.pieces(Us, PAWN) & ~TRank7BB;
 
     // Single and double pawn pushes, no promotions
-    if (Type != CAPTURES)
+    if constexpr (Type != CAPTURES)
     {
         Bitboard b1 = shift<Up>(pawnsNotOn7)   & emptySquares;
         Bitboard b2 = shift<Up>(b1 & TRank3BB) & emptySquares;
 
-        if (Type == EVASIONS) // Consider only blocking squares
+        if constexpr (Type == EVASIONS) // Consider only blocking squares
         {
             b1 &= target;
             b2 &= target;
         }
 
-        if (Type == QUIET_CHECKS)
+        if constexpr (Type == QUIET_CHECKS)
         {
             // To make a quiet check, you either make a direct check by pushing a pawn
             // or push a blocker pawn that is not on the same file as the enemy king.
@@ -102,7 +102,7 @@ namespace {
         Bitboard b2 = shift<UpLeft >(pawnsOn7) & enemies;
         Bitboard b3 = shift<Up     >(pawnsOn7) & emptySquares;
 
-        if (Type == EVASIONS)
+        if constexpr (Type == EVASIONS)
             b3 &= target;
 
         while (b1)
@@ -116,7 +116,7 @@ namespace {
     }
 
     // Standard and en passant captures
-    if (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
+    if constexpr (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
     {
         Bitboard b1 = shift<UpRight>(pawnsNotOn7) & enemies;
         Bitboard b2 = shift<UpLeft >(pawnsNotOn7) & enemies;
diff --git a/src/movepick.cpp b/src/movepick.cpp
index dbe67357..65155a73 100644
--- a/src/movepick.cpp
+++ b/src/movepick.cpp
@@ -158,7 +158,7 @@ Move MovePicker::select(Pred filter) {
 
   while (cur < endMoves)
   {
-      if (T == Best)
+      if constexpr (T == Best)
           std::swap(*cur, *std::max_element(cur, endMoves));
 
       if (*cur != ttMove && filter())
-- 
2.39.2