Merge pull request #189 from corwinkuiper/perfectly-poor-profiler

Problematic poor person's profiler

agb/examples/sprites.rs

@@ -5,6 +5,7 @@ extern crate alloc;
 
 use agb::display::object::{Graphics, ObjectController, Sprite, TagMap};
 use alloc::vec::Vec;
+use bare_metal::CriticalSection;
 
 const GRAPHICS: &Graphics = agb::include_aseprite!(
     "../examples/the-purple-night/gfx/objects.aseprite",
@@ -100,6 +101,10 @@ fn all_tags(gfx: &ObjectController) {
 fn main(mut gba: agb::Gba) -> ! {
     let gfx = gba.display.object.get();
 
+    let mut timers = gba.timers.timers();
+
+    let _a = agb::interrupt::profiler(&mut timers.timer0, 5000);
+
     loop {
         all_tags(&gfx);
         all_sprites(&gfx);

agb/interrupt_handler.s

@@ -1,3 +1,4 @@
+
 @ An interrupt handler that simply acknowledges all interrupts
     .arm
     .global InterruptHandler
@@ -14,6 +15,10 @@ InterruptHandler:
     ldrh r3, [r2, #2] @ load 16 bit interrupt request to r3
     and r0, r1, r3 @ interrupts both enabled and requested
 
+    ldr r1, [sp, #20]
+    ldr r3, =agb_rs__program_counter
+    str r1, [r3]
+
     @ change to system mode
     mrs r1, cpsr
     orr r1, r1, #0xD
@@ -43,3 +48,10 @@ InterruptHandler:
 
     bx lr @ return to bios
 .pool
+
+
+.section .iwram
+    .global agb_rs__program_counter
+    .balign 4
+agb_rs__program_counter:
+    .word 0

agb/src/interrupt.rs

@@ -360,3 +360,22 @@ mod tests {
         );
     }
 }
+
+#[must_use]
+/// The behaviour of this function is undefined in the sense that it will output
+/// some information in some way that can be interpreted in a way to give some
+/// profiling information. What it outputs, how it outputs it, and how to
+/// interpret it are all subject to change at any time.
+///
+/// With that out of the way, the current version will, in mgba, output the
+/// program counter at regular intervals. This can be used to see hot functions
+/// using, for example, addr2line.
+pub fn profiler(timer: &mut crate::timer::Timer, period: u16) -> InterruptHandler {
+    timer.set_interrupt(true);
+    timer.set_overflow_amount(period);
+    timer.set_enabled(true);
+
+    add_interrupt_handler(timer.get_interrupt(), |_key: &CriticalSection| {
+        crate::println!("{:#010x}", crate::get_program_counter_before_interrupt());
+    })
+}

agb/src/lib.rs

@@ -407,3 +407,11 @@ mod test {
         }
     }
 }
+
+#[inline(never)]
+pub fn get_program_counter_before_interrupt() -> u32 {
+    extern "C" {
+        static mut agb_rs__program_counter: u32;
+    }
+    unsafe { agb_rs__program_counter }
+}

agb/src/timer.rs

@@ -90,6 +90,11 @@ impl Timer {
         self.control_register().set_bits(bit, 1, 2);
     }
 
+    pub fn set_interrupt(&mut self, interrupt: bool) {
+        let bit = interrupt as u16;
+        self.control_register().set_bits(bit, 1, 6);
+    }
+
     fn data_register(&self) -> MemoryMapped<u16> {
         timer_data(self.get_timer_number())
     }
@@ -101,6 +106,17 @@ impl Timer {
     fn get_timer_number(&self) -> usize {
         self.timer_number as usize
     }
+
+    pub fn get_interrupt(&self) -> crate::interrupt::Interrupt {
+        use crate::interrupt::Interrupt;
+        match self.timer_number {
+            0 => Interrupt::Timer0,
+            1 => Interrupt::Timer1,
+            2 => Interrupt::Timer2,
+            3 => Interrupt::Timer3,
+            _ => unreachable!(),
+        }
+    }
 }
 
 #[non_exhaustive]