added scopes

lib/p2/src/structures/pscopes.zig

@@ -0,0 +1,131 @@
+// pscopes
+//
+// a tiny scope based profiling library
+//
+// as well as contains info for arbitrary timestamping and timestamp resolution
+
+const timestampTicks = if (builtin.target.cpu.arch == .x86_64) aarch64_ticks else rdtsc;
+
+pub inline fn rdtsc_fenced() u64 {
+    var hi: u32 = 0;
+    var low: u32 = 0;
+
+    asm (
+        \\rdtsc
+        \\mfence
+        : [low] "={eax}" (low),
+          [hi] "={edx}" (hi),
+    );
+    return (@as(u64, hi) << 32) | @as(u64, low);
+}
+
+// rdtsc actually gets read
+pub inline fn rdtsc() u64 {
+    var hi: u32 = 0;
+    var low: u32 = 0;
+
+    asm (
+        \\rdtsc
+        : [low] "={eax}" (low),
+          [hi] "={edx}" (hi),
+    );
+    return (@as(u64, hi) << 32) | @as(u64, low);
+}
+
+fn aarch64_ticks() u64 {
+    return asm volatile ("mrs %[ret], CNTVCT_EL0"
+        : [ret] "=r" (-> u64),
+    );
+}
+
+fn aarch64_freq() u64 {
+    return asm volatile ("mrs %[ret], CNTFRQ_EL0"
+        : [ret] "=r" (-> u64),
+    );
+}
+
+pub const TimingScope = struct {
+    // value in tsc ticks
+    startTsc: u64,
+    endTsc: ?u64 = null,
+
+    context: *ScopesContext,
+
+    pub inline fn init(c: *ScopesContext) @This() {
+        return .{
+            .startTsc = rdtsc(),
+            .context = c,
+        };
+    }
+
+    pub fn duration(self: *@This()) ?f64 {
+        _ = self;
+    }
+
+    pub inline fn end(self: *@This()) void {
+        self.endTsc = rdtsc();
+    }
+};
+
+pub const ScopesContext = struct {
+    allocator: std.mem.Allocator,
+    ticksPerMs: ?f64 = null,
+    timer: std.time.Timer,
+
+    pub fn timingScope(self: *@This()) TimingScope {
+        _ = self;
+    }
+
+    // calibrates the ticks per second divider.
+    // spins for 1 ms then compares against the monotonic timer
+    // should be called once every second
+    pub fn calibrate(self: *@This()) void {
+        if (builtin.target.cpu.arch == .x86_64) {
+            self.timer.reset();
+            const startStamp = rdtsc();
+            while (self.timer.read() < std.time.ns_per_ms) {}
+            const endStamp = rdtsc();
+
+            self.ticksPerMs = @floatFromInt((endStamp - startStamp));
+        } else if (builtin.target.cpu.arch == .aarch64) {
+            self.ticksPerMs = @as(f64, @floatFromInt(aarch64_freq())) / 1000;
+        } else {
+            // not ticking
+            // unreachable;
+        }
+    }
+
+    pub fn create(allocator: std.mem.Allocator) !*@This() {
+        const self = try allocator.create(@This());
+        self.* = .{
+            .allocator = allocator,
+            .timer = try std.time.Timer.start(),
+        };
+        return self;
+    }
+
+    pub fn destroy(self: *@This()) void {
+        self.allocator.destroy(self);
+    }
+};
+
+test "calibrate scoes" {
+    const allocator = std.testing.allocator;
+
+    const scopes = try ScopesContext.create(allocator);
+    defer scopes.destroy();
+    scopes.calibrate();
+
+    std.debug.print("calibration ticksPerMs = {d}\n", .{scopes.ticksPerMs.?});
+    scopes.calibrate();
+    std.debug.print("calibration ticksPerMs = {d}\n", .{scopes.ticksPerMs.?});
+    scopes.calibrate();
+    std.debug.print("calibration ticksPerMs = {d}\n", .{scopes.ticksPerMs.?});
+    scopes.calibrate();
+    std.debug.print("calibration ticksPerMs = {d}\n", .{scopes.ticksPerMs.?});
+    scopes.calibrate();
+    std.debug.print("calibration ticksPerMs = {d}\n", .{scopes.ticksPerMs.?});
+}
+
+const std = @import("std");
+const builtin = @import("builtin");