From 67d516fcee95ffd21843bca1d5c821f8afa9b4e7 Mon Sep 17 00:00:00 2001
From: tildearrow <tildearrow@protonmail.com>
Date: Mon, 14 Mar 2022 01:38:11 -0500
Subject: [PATCH] Genesis: prioritize DAC writes

---
 src/engine/platform/genesis.cpp     | 10 +++++-----
 src/engine/platform/genesis.h       |  4 ++--
 src/engine/platform/genesisshared.h |  3 ++-
 3 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/src/engine/platform/genesis.cpp b/src/engine/platform/genesis.cpp
index b3096e72a..75c54af68 100644
--- a/src/engine/platform/genesis.cpp
+++ b/src/engine/platform/genesis.cpp
@@ -92,7 +92,7 @@ void DivPlatformGenesis::acquire_nuked(short* bufL, short* bufR, size_t start, s
         DivSample* s=parent->getSample(dacSample);
         if (s->samples>0) {
           if (!isMuted[5]) {
-            immWrite(0x2a,(unsigned char)s->data8[dacPos]+0x80);
+            urgentWrite(0x2a,(unsigned char)s->data8[dacPos]+0x80);
           }
           if (++dacPos>=s->samples) {
             if (s->loopStart>=0 && s->loopStart<=(int)s->samples) {
@@ -121,7 +121,7 @@ void DivPlatformGenesis::acquire_nuked(short* bufL, short* bufR, size_t start, s
           //printf("write: %x = %.2x\n",w.addr,w.val);
           lastBusy=0;
           regPool[w.addr&0x1ff]=w.val;
-          writes.pop();
+          writes.pop_front();
         } else {
           lastBusy++;
           if (fm.write_busy==0) {
@@ -159,7 +159,7 @@ void DivPlatformGenesis::acquire_ymfm(short* bufL, short* bufR, size_t start, si
         DivSample* s=parent->getSample(dacSample);
         if (s->samples>0) {
           if (!isMuted[5]) {
-            immWrite(0x2a,(unsigned char)s->data8[dacPos]+0x80);
+            urgentWrite(0x2a,(unsigned char)s->data8[dacPos]+0x80);
           }
           if (++dacPos>=s->samples) {
             if (s->loopStart>=0 && s->loopStart<=(int)s->samples) {
@@ -184,7 +184,7 @@ void DivPlatformGenesis::acquire_ymfm(short* bufL, short* bufR, size_t start, si
       fm_ymfm->write(0x0+((w.addr>>8)<<1),w.addr);
       fm_ymfm->write(0x1+((w.addr>>8)<<1),w.val);
       regPool[w.addr&0x1ff]=w.val;
-      writes.pop();
+      writes.pop_front();
       lastBusy=1;
     }
     
@@ -782,7 +782,7 @@ int DivPlatformGenesis::getRegisterPoolSize() {
 }
 
 void DivPlatformGenesis::reset() {
-  while (!writes.empty()) writes.pop();
+  while (!writes.empty()) writes.pop_front();
   memset(regPool,0,512);
   if (useYMFM) {
     fm_ymfm->reset();
diff --git a/src/engine/platform/genesis.h b/src/engine/platform/genesis.h
index cd7b0396c..095744dfe 100644
--- a/src/engine/platform/genesis.h
+++ b/src/engine/platform/genesis.h
@@ -20,7 +20,7 @@
 #ifndef _GENESIS_H
 #define _GENESIS_H
 #include "../dispatch.h"
-#include <queue>
+#include <deque>
 #include "../../../extern/Nuked-OPN2/ym3438.h"
 #include "sound/ymfm/ymfm_opn.h"
 
@@ -68,7 +68,7 @@ class DivPlatformGenesis: public DivDispatch {
       bool addrOrVal;
       QueuedWrite(unsigned short a, unsigned char v): addr(a), val(v), addrOrVal(false) {}
     };
-    std::queue<QueuedWrite> writes;
+    std::deque<QueuedWrite> writes;
     ym3438_t fm;
     int delay;
     unsigned char lastBusy;
diff --git a/src/engine/platform/genesisshared.h b/src/engine/platform/genesisshared.h
index d2402a60d..01d45f955 100644
--- a/src/engine/platform/genesisshared.h
+++ b/src/engine/platform/genesisshared.h
@@ -43,6 +43,7 @@ static int orderedOps[4]={
 };
 
 #define rWrite(a,v) if (!skipRegisterWrites) {pendingWrites[a]=v;}
-#define immWrite(a,v) if (!skipRegisterWrites) {writes.emplace(a,v); if (dumpWrites) {addWrite(a,v);} }
+#define immWrite(a,v) if (!skipRegisterWrites) {writes.push_back(QueuedWrite(a,v)); if (dumpWrites) {addWrite(a,v);} }
+#define urgentWrite(a,v) if (!skipRegisterWrites) {if (writes.front().addrOrVal) {writes.push_back(QueuedWrite(a,v));} else {writes.push_front(QueuedWrite(a,v));}; if (dumpWrites) {addWrite(a,v);} }
 
 #include "fmshared_OPN.h"