From 0f643e01b733b1e59f9a9eb17c7582a399b31a42 Mon Sep 17 00:00:00 2001
From: Lior Halphon <LIJI32@gmail.com>
Date: Fri, 8 Sep 2017 12:58:35 +0300
Subject: [PATCH] Removing the delayed interrupt mechanism, research is not
 complete enough for implementation

---
 Core/display.c | 11 -----------
 Core/gb.h      |  1 -
 Core/timing.c  |  3 +--
 Core/z80_cpu.c |  2 +-
 4 files changed, 2 insertions(+), 15 deletions(-)

diff --git a/Core/display.c b/Core/display.c
index 4def6c8..ae0e77f 100755
--- a/Core/display.c
+++ b/Core/display.c
@@ -300,7 +300,6 @@ static void update_display_state(GB_gameboy_t *gb, uint8_t cycles)
     uint8_t vram_blocking_rush = gb->is_cgb? 0 : 4;
     
     for (; cycles; cycles -= atomic_increase) {
-        gb->delayed_interrupts &= ~3;
         gb->display_cycles += atomic_increase;
         /* The very first line is 4 clocks shorter when the LCD turns on. Verified on SGB2, CGB in CGB mode and
          CGB in double speed mode. */
@@ -344,10 +343,6 @@ static void update_display_state(GB_gameboy_t *gb, uint8_t cycles)
             gb->io_registers[GB_IO_STAT] &= ~3;
             gb->io_registers[GB_IO_STAT] |= 1;
             gb->io_registers[GB_IO_IF] |= 1;
-            if (gb->is_cgb) {
-                /* See comment on STAT interrupt at the end of the loop */
-                gb->delayed_interrupts |= 1;
-            }
             
             /* Entering VBlank state triggers the OAM interrupt. In CGB, it happens 4 cycles earlier */
             if (gb->io_registers[GB_IO_STAT] & 0x20 && !gb->is_cgb) {
@@ -563,12 +558,6 @@ static void update_display_state(GB_gameboy_t *gb, uint8_t cycles)
     
     if (gb->stat_interrupt_line && !previous_stat_interrupt_line) {
         gb->io_registers[GB_IO_IF] |= 2;
-        if (gb->is_cgb) {
-            /* On CGB, the STAT interrupt is not aligned to a T-Cycle, therefore it is only effective the next T-Cycle
-               Todo: verify on DMG mode CGB. This was only tested on LYC STAT interrupts, should be tested on others
-               as well. */
-            gb->delayed_interrupts |= 2;
-        }
     }
     
 #if 0
diff --git a/Core/gb.h b/Core/gb.h
index 773dccc..c18bf30 100644
--- a/Core/gb.h
+++ b/Core/gb.h
@@ -332,7 +332,6 @@ struct GB_gameboy_internal_s {
         GB_PADDING(uint16_t, serial_cycles);
         uint16_t serial_cycles; /* This field changed its meaning in v0.10 */
         uint16_t serial_length;
-        uint8_t delayed_interrupts; /* When an interrupt occurs while not aligned to a T-cycle, it must be "delayed" */
         bool dont_delay_timer_interrupt; /* If the timer glitch causes a TIMA overflow, it causes the timer to overflow
                                             with different timing, so the triggered interrupt is not delayed.
                                             Todo: needs test ROM. */
diff --git a/Core/timing.c b/Core/timing.c
index 626cb45..e5ac788 100644
--- a/Core/timing.c
+++ b/Core/timing.c
@@ -82,14 +82,13 @@ static void GB_ir_run(GB_gameboy_t *gb)
 
 static void advance_tima_state_machine(GB_gameboy_t *gb)
 {
-    gb->delayed_interrupts &= ~4;
     if (gb->tima_reload_state == GB_TIMA_RELOADED) {
         gb->tima_reload_state = GB_TIMA_RUNNING;
     }
     else if (gb->tima_reload_state == GB_TIMA_RELOADING) {
         gb->io_registers[GB_IO_IF] |= 4;
         if (!gb->dont_delay_timer_interrupt) {
-            gb->delayed_interrupts |= 4; // Timer interrupt is not aligned to a T-cycle and therefore is effective only the next one.
+            // Todo
         }
         gb->tima_reload_state = GB_TIMA_RELOADED;
     }
diff --git a/Core/z80_cpu.c b/Core/z80_cpu.c
index b6dde8a..ce30d55 100644
--- a/Core/z80_cpu.c
+++ b/Core/z80_cpu.c
@@ -1337,7 +1337,7 @@ static GB_opcode_t *opcodes[256] = {
 void GB_cpu_run(GB_gameboy_t *gb)
 {
     gb->vblank_just_occured = false;
-    uint8_t interrupt_queue = gb->interrupt_enable & gb->io_registers[GB_IO_IF] & 0x1F  & ~gb->delayed_interrupts;
+    uint8_t interrupt_queue = gb->interrupt_enable & gb->io_registers[GB_IO_IF] & 0x1F;
 
     if (interrupt_queue) {
         gb->halted = false;