test ppu updates during vblank

while testing this i found that updating the score, lines, and hz
display all in the same frame takes too long. currently this isn't an
issue because negative delay doesn't go back that far, but if needed
there are several ways to optimize this (e.g. delay the hz update until
the next piece spawn, don't update hz during entry delay, etc.)

Author: fractal161

src/nmi/render_mode_play_and_demo.asm

@@ -93,7 +93,7 @@ render_mode_play_and_demo:
         and #RENDER_SCORE
         beq @renderHz
 
-        ; 8 safe tile writes freed from stats / hz
+        ; 9 safe tile writes freed from stats / hz
         ; (lazy render hz for 10 more)
         ; 1 added in level (3 total)
         ; 2 added in lines (5 total)

tests/src/main.rs

@@ -17,6 +17,7 @@ mod sps;
 mod toprow;
 mod tspins;
 mod hz_display;
+mod nmi;
 
 use gumdrop::Options;
 
@@ -47,7 +48,7 @@ struct TestOptions {
 fn main() {
     let options = TestOptions::parse_args_default_or_exit();
 
-    let tests: [(&str, fn()); 11] = [
+    let tests: [(&str, fn()); 12] = [
         ("garbage4", garbage::test_garbage4_crash),
         ("floor", floor::test),
         ("tspins", tspins::test),
@@ -59,6 +60,7 @@ fn main() {
         ("sps", sps::test),
         ("palettes", palettes::test),
         ("hz_display", hz_display::test),
+        ("nmi", nmi::test),
     ];
 
     // run tests

tests/src/nmi.rs

@@ -0,0 +1,73 @@
+use crate::{labels, playfield, util};
+
+/// makes sure nmi exits quickly enough
+pub fn test() {
+    let mut emu = util::emulator(None);
+
+    let main_loop = labels::get("mainLoop");
+    let game_mode = labels::get("gameMode") as usize;
+    let level_number = labels::get("levelNumber") as usize;
+    let nmi_label = labels::get("nmi");
+    let hz_flag = labels::get("hzFlag") as usize;
+    let render_flags = labels::get("renderFlags") as usize;
+
+    // spend a few frames bootstrapping
+    for _ in 0..3 {
+        emu.run_until_vblank();
+    }
+
+    // copied setup from garbage.rs
+    emu.memory.iram_raw[hz_flag] = 1;
+    emu.memory.iram_raw[game_mode] = 4;
+    emu.memory.iram_raw[level_number] = 18;
+    emu.registers.pc = main_loop;
+
+    for _ in 0..11 {
+        emu.run_until_vblank();
+    }
+
+    // sets up a triple in the top of the board
+    emu.memory.iram_raw[labels::get("currentPiece") as usize] = 0x0F; // L piece
+    emu.memory.iram_raw[labels::get("tetriminoX") as usize] = 0x6;
+    emu.memory.iram_raw[labels::get("tetriminoY") as usize] = 0x0;
+    emu.memory.iram_raw[labels::get("vramRow") as usize] = 0;
+    emu.memory.iram_raw[labels::get("autorepeatY") as usize] = 0;
+
+    playfield::set_str(&mut emu, r##"
+#####  ###
+#####  ###
+###### ###
+###### ###
+######### 
+######### 
+######### 
+######### 
+######### 
+######### 
+######### 
+######### 
+######### 
+######### 
+######### 
+######### 
+######### 
+######### 
+######### 
+######### "##);
+
+    for _ in 0..50 {
+        // loop until pc is at the instruction after the jsr copyOamStagingToOam
+        while emu.registers.pc != nmi_label + 25 {
+            emu.step();
+            if emu.ppu.current_scanline == 261 {
+                panic!("render took too long!");
+            }
+        }
+        // cannot render hz on the same frame score/lines are updated
+        let state = emu.memory.iram_raw[labels::get("playState") as usize];
+        if state != 5 {
+            emu.memory.iram_raw[render_flags] |= 0x10;
+        }
+        emu.run_until_vblank();
+    }
+}