SCC: massive optimization

extern/vgsound_emu-modified/vgsound_emu/src/scc/README.md

@@ -1,5 +1,9 @@
 # Konami SCC
 
+## modified
+
+the emulation core has been modified for optimization.
+
 ## Summary
 
 - 5 voice wavetable

extern/vgsound_emu-modified/vgsound_emu/src/scc/scc.cpp

@@ -10,17 +10,17 @@
 #include "scc.hpp"
 
 // shared SCC features
-void scc_core::tick()
+void scc_core::tick(const int cycles)
 {
 	m_out = 0;
 	for (auto &elem : m_voice)
 	{
-		elem.tick();
+		elem.tick(cycles);
 		m_out += elem.out();
 	}
 }
 
-void scc_core::voice_t::tick()
+void scc_core::voice_t::tick(const int cycles)
 {
 	if (m_pitch >= 9)  // or voice is halted
 	{
@@ -28,23 +28,23 @@ void scc_core::voice_t::tick()
 		const u16 temp = m_counter;
 		if (m_host.m_test.freq_4bit())	// 4 bit frequency mode
 		{
-			m_counter = (m_counter & ~0x0ff) | (bitfield(bitfield(m_counter, 0, 8) - 1, 0, 8) << 0);
-			m_counter = (m_counter & ~0xf00) | (bitfield(bitfield(m_counter, 8, 4) - 1, 0, 4) << 8);
+			m_counter = (m_counter & ~0x0ff) | (bitfield(bitfield(m_counter, 0, 8) - cycles, 0, 8) << 0);
+			m_counter = (m_counter & ~0xf00) | (bitfield(bitfield(m_counter, 8, 4) - cycles, 0, 4) << 8);
 		}
 		else
 		{
-			m_counter = bitfield(m_counter - 1, 0, 12);
+			m_counter = bitfield(m_counter - cycles, 0, 12);
 		}
 
 		// handle counter carry
-		const bool carry = m_host.m_test.freq_8bit()
+		const bool carry = (temp<cycles) || (m_host.m_test.freq_8bit()
 						   ? (bitfield(temp, 0, 8) == 0)
 						   : (m_host.m_test.freq_4bit() ? (bitfield(temp, 8, 4) == 0)
-														: (bitfield(temp, 0, 12) == 0));
+														: (bitfield(temp, 0, 12) == 0)));
 		if (carry)
 		{
 			m_addr	  = bitfield(m_addr + 1, 0, 5);
-			m_counter = m_pitch;
+			m_counter = m_pitch - ((temp<cycles)?(cycles-temp-1):0);
 		}
 	}
 	// get output

extern/vgsound_emu-modified/vgsound_emu/src/scc/scc.hpp

@@ -41,7 +41,7 @@ class scc_core : public vgsound_emu_core
 
 				// internal state
 				void reset();
-				void tick();
+				void tick(const int cycles=1);
 
 				// accessors
 				inline void reset_addr() { m_addr = 0; }
@@ -151,7 +151,7 @@ class scc_core : public vgsound_emu_core
 
 		// internal state
 		virtual void reset();
-		void tick();
+		void tick(const int cycles=1);
 
 		// getters
 		inline s32 out() { return m_out; }	// output to DA0...DA10 pin

src/engine/platform/scc.cpp

@@ -82,9 +82,7 @@ const char** DivPlatformSCC::getRegisterSheet() {
 
 void DivPlatformSCC::acquire(short** buf, size_t len) {
   for (size_t h=0; h<len; h++) {
-    for (int i=0; i<16; i++) {
-      scc->tick();
-    }
+    scc->tick(16);
     short out=(short)scc->out()<<5;
     buf[0][h]=out;