From 4b03cc05c1ab5b94cebf50b90bb8b187875b91b6 Mon Sep 17 00:00:00 2001
From: Lior Halphon <LIJI32@gmail.com>
Date: Sun, 24 Jul 2022 13:16:19 +0300
Subject: [PATCH] Optimization to joypad code

---
 Core/gb.h     | 1 +
 Core/joypad.c | 7 +++++++
 Core/memory.c | 1 +
 3 files changed, 9 insertions(+)

diff --git a/Core/gb.h b/Core/gb.h
index c5404a5..63f02fe 100644
--- a/Core/gb.h
+++ b/Core/gb.h
@@ -689,6 +689,7 @@ struct GB_gameboy_internal_s {
         bool joyp_accessed;
         bool illegal_inputs_allowed;
         bool no_bouncing_emulation;
+        bool joypad_is_stable;
 
         /* Timing */
         uint64_t last_sync;
diff --git a/Core/joypad.c b/Core/joypad.c
index b4e3cf9..2f47c60 100644
--- a/Core/joypad.c
+++ b/Core/joypad.c
@@ -132,6 +132,7 @@ void GB_set_key_state_for_player(GB_gameboy_t *gb, GB_key_t index, unsigned play
     assert(index >= 0 && index < GB_KEY_MAX);
     assert(player < 4);
     if (should_bounce(gb) && pressed != gb->keys[player][index]) {
+        gb->joypad_is_stable = false;
         gb->key_bounce_timing[index] = bounce_for_key(gb, index);
     }
     gb->keys[player][index] = pressed;
@@ -143,6 +144,7 @@ void GB_set_key_mask(GB_gameboy_t *gb, GB_key_mask_t mask)
     for (unsigned i = 0; i < GB_KEY_MAX; i++) {
         bool pressed = mask & (1 << i);
         if (should_bounce(gb) && pressed != gb->keys[0][i]) {
+            gb->joypad_is_stable = false;
             gb->key_bounce_timing[i] = bounce_for_key(gb, i);
         }
         gb->keys[0][i] = pressed;
@@ -156,6 +158,7 @@ void GB_set_key_mask_for_player(GB_gameboy_t *gb, GB_key_mask_t mask, unsigned p
     for (unsigned i = 0; i < GB_KEY_MAX; i++) {
         bool pressed = mask & (1 << i);
         if (should_bounce(gb) && pressed != gb->keys[player][i]) {
+            gb->joypad_is_stable = false;
             gb->key_bounce_timing[i] = bounce_for_key(gb, i);
         }
         gb->keys[player][i] = pressed;
@@ -166,8 +169,11 @@ void GB_set_key_mask_for_player(GB_gameboy_t *gb, GB_key_mask_t mask, unsigned p
 
 void GB_joypad_run(GB_gameboy_t *gb, unsigned cycles)
 {
+    if (gb->joypad_is_stable) return;
     bool should_update_joyp = false;
+    gb->joypad_is_stable = true;
     if (gb->joyp_switching_delay) {
+        gb->joypad_is_stable = false;
         if (gb->joyp_switching_delay > cycles) {
             gb->joyp_switching_delay -= cycles;
         }
@@ -180,6 +186,7 @@ void GB_joypad_run(GB_gameboy_t *gb, unsigned cycles)
     
     for (unsigned i = 0; i < GB_KEY_MAX; i++) {
         if (gb->key_bounce_timing[i]) {
+            gb->joypad_is_stable = false;
             should_update_joyp = true;
             if (gb->key_bounce_timing[i] > cycles) {
                 gb->key_bounce_timing[i] -= cycles;
diff --git a/Core/memory.c b/Core/memory.c
index 6bbc949..8c454cf 100644
--- a/Core/memory.c
+++ b/Core/memory.c
@@ -1508,6 +1508,7 @@ static void write_high_memory(GB_gameboy_t *gb, uint16_t addr, uint8_t value)
                         gb->joyp_switch_value = value;
                         gb->joyp_switching_delay = 24;
                         value &= gb->io_registers[GB_IO_JOYP];
+                        gb->joypad_is_stable = false;
                     }
                     GB_sgb_write(gb, value);
                     gb->io_registers[GB_IO_JOYP] = (value & 0xF0) | (gb->io_registers[GB_IO_JOYP] & 0x0F);