From 78e7c0bc3f9baab5bf58411db37aa7769d8cb7a3 Mon Sep 17 00:00:00 2001
From: Rekai Musuka <rekai@musuka.dev>
Date: Fri, 21 Oct 2022 05:12:45 -0300
Subject: [PATCH] perf: don't check scheduler every iteration of runFrame loop

~20fps gain in Pokemon Emerald, nice
---
 src/emu.zig | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/emu.zig b/src/emu.zig
index 193c0eb..002874c 100644
--- a/src/emu.zig
+++ b/src/emu.zig
@@ -50,14 +50,17 @@ pub fn run(kind: RunKind, quit: *Atomic(bool), fps: *FpsTracker, sched: *Schedul
 pub fn runFrame(sched: *Scheduler, cpu: *Arm7tdmi) void {
     const frame_end = sched.tick + cycles_per_frame;
 
-    while (sched.tick < frame_end) {
-        if (cpu.bus.io.haltcnt == .Halt) sched.tick += 1;
-        if (cpu.bus.io.haltcnt == .Execute) cpu.step();
-        cpu.handleDMATransfers();
+    while (true) {
+        const next = sched.nextTimestamp();
+        const run_until = std.math.min(next, frame_end);
 
-        while (sched.tick >= sched.nextTimestamp()) {
-            sched.handleEvent(cpu);
+        while (sched.tick < run_until) {
+            if (cpu.bus.io.haltcnt == .Execute) cpu.step() else sched.tick += 1;
+            cpu.handleDMATransfers();
         }
+
+        if (sched.tick >= frame_end) break;
+        sched.handleEvent(cpu);
     }
 }