From 4392ed6988b9bbc9b633d3a0a190aa60da0cd54b Mon Sep 17 00:00:00 2001
From: Michel Kremer <kremi151dev@gmail.com>
Date: Mon, 28 Dec 2020 23:04:10 +0100
Subject: [PATCH] Access IO registers directly in doTimers (#20)

---
 core/source/emulator/cpu.cpp        | 10 +++++-----
 core/source/emulator/io_registers.h | 15 +++++++++++++++
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/core/source/emulator/cpu.cpp b/core/source/emulator/cpu.cpp
index 975b70ab..b4cbc7f7 100644
--- a/core/source/emulator/cpu.cpp
+++ b/core/source/emulator/cpu.cpp
@@ -341,25 +341,25 @@ void CPU::doTimers(Memory &memory, u8 clocks) {
         timerOverflowingCycles -= clocks;
         if (timerOverflowingCycles <= 0) {
             //fprintf(stdout, "# Request Timer interrupt\n");
-            memory.write8BitsTo(FB_REG_TIMA, memory.read8BitsAt(FB_REG_TMA));
+            ioRegisters.getTIMA() = ioRegisters.getTMA();
             requestInterrupt(InterruptType::TIMER);
             timerOverflowingCycles = -1;
         }
     }
-    u8 tac = memory.read8BitsAt(FB_REG_TAC);
+    u8 tac = ioRegisters.getTAC();
     bool comp1 = (tac & 0b100u) != 0;
     comp1 &= doTimerObscureCheck(clocks, sysCounter, tac);
     // Falling edge detector
     if (delayedTIMAIncrease && !comp1) {
-        u8 tima = memory.read8BitsAt(FB_REG_TIMA);
+        u8 tima = ioRegisters.getTIMA();
         if (tima == 0xff) {
             //fprintf(stdout, "# TIMA has overflown\n");
             // Delay TIMA load by 1 m-cycle
             timerOverflowingCycles = 4;
             // In the meantime, set TIMA to 0
-            memory.write8BitsTo(FB_REG_TIMA, 0x00);
+            ioRegisters.getTIMA() = 0x00;
         } else if (timerOverflowingCycles == -1) { // TIME has to be 0 for one full m-cycle, so we do not increase here in that case
-            memory.write8BitsTo(FB_REG_TIMA, tima + 1);
+            ioRegisters.getTIMA() = tima + 1;
         }
     }
     delayedTIMAIncrease = comp1;
diff --git a/core/source/emulator/io_registers.h b/core/source/emulator/io_registers.h
index a61a3848..7b2637e2 100644
--- a/core/source/emulator/io_registers.h
+++ b/core/source/emulator/io_registers.h
@@ -46,6 +46,9 @@
 
 #define __FB_REG_OFFSET_P1 (FB_REG_P1 - 0xFF00)
 #define __FB_REG_OFFSET_DIV (FB_REG_DIV - 0xFF00)
+#define __FB_REG_OFFSET_TIMA (FB_REG_TIMA - 0xFF00)
+#define __FB_REG_OFFSET_TMA (FB_REG_TMA - 0xFF00)
+#define __FB_REG_OFFSET_TAC (FB_REG_TAC - 0xFF00)
 #define __FB_REG_OFFSET_IF (FB_REG_IF - 0xFF00)
 #define __FB_REG_OFFSET_LCDC (FB_REG_LCDC - 0xFF00)
 #define __FB_REG_OFFSET_STAT (FB_REG_STAT - 0xFF00)
@@ -92,6 +95,18 @@ namespace FunkyBoy {
             return *(hwIO + __FB_REG_OFFSET_P1);
         }
 
+        inline u8 &getTIMA() {
+            return *(hwIO + __FB_REG_OFFSET_TIMA);
+        }
+
+        inline u8 &getTMA() {
+            return *(hwIO + __FB_REG_OFFSET_TMA);
+        }
+
+        inline u8 &getTAC() {
+            return *(hwIO + __FB_REG_OFFSET_TAC);
+        }
+
         inline u8 &getIF() {
             return *(hwIO + __FB_REG_OFFSET_IF);
         }