Add benchmarks for V8 native function calls (#1079)

Cargo.toml

@@ -106,5 +106,10 @@ name = "process"
 name = "build"
 path = "build.rs"
 
+[[bench]]
+name = "function"
+path = "benches/function.rs"
+harness = false
+
 [workspace]
 members = ["examples/android"]

benches/function.rs

@@ -0,0 +1,135 @@
+use std::os::raw::c_void;
+
+fn main() {
+  v8::V8::set_flags_from_string(
+    "--turbo_fast_api_calls --allow_natives_syntax",
+  );
+  let platform = v8::new_default_platform(0, false).make_shared();
+  v8::V8::initialize_platform(platform);
+  v8::V8::initialize();
+  let isolate = &mut v8::Isolate::new(v8::CreateParams::default());
+  let handle_scope = &mut v8::HandleScope::new(isolate);
+  let context = v8::Context::new(handle_scope);
+  let scope = &mut v8::ContextScope::new(handle_scope, context);
+  let global = context.global(scope);
+  {
+    let func = v8::Function::new(
+      scope,
+      |scope: &mut v8::HandleScope,
+       _: v8::FunctionCallbackArguments,
+       mut rv: v8::ReturnValue| {
+        rv.set(v8::Integer::new(scope, 42).into());
+      },
+    )
+    .unwrap();
+    let name = v8::String::new(scope, "new_").unwrap();
+    global.set(scope, name.into(), func.into()).unwrap();
+  }
+  {
+    extern "C" fn callback(info: *const v8::FunctionCallbackInfo) {
+      let scope = unsafe { &mut v8::CallbackScope::new(&*info) };
+      let mut rv =
+        unsafe { v8::ReturnValue::from_function_callback_info(info) };
+      rv.set(v8::Integer::new(scope, 42).into());
+    }
+    let func = v8::Function::new_raw(scope, callback).unwrap();
+    let name = v8::String::new(scope, "new_raw").unwrap();
+    global.set(scope, name.into(), func.into()).unwrap();
+  }
+  {
+    extern "C" fn callback(info: *const v8::FunctionCallbackInfo) {
+      let mut rv =
+        unsafe { v8::ReturnValue::from_function_callback_info(info) };
+      rv.set_uint32(42);
+    }
+    let func = v8::Function::new_raw(scope, callback).unwrap();
+    let name = v8::String::new(scope, "new_raw_set_uint32").unwrap();
+    global.set(scope, name.into(), func.into()).unwrap();
+  }
+  {
+    let func = v8::Function::new(
+      scope,
+      |_: &mut v8::HandleScope,
+       _: v8::FunctionCallbackArguments,
+       mut rv: v8::ReturnValue| {
+        rv.set_uint32(42);
+      },
+    )
+    .unwrap();
+    let name = v8::String::new(scope, "new_set_uint32").unwrap();
+    global.set(scope, name.into(), func.into()).unwrap();
+  }
+  {
+    fn fast_fn() -> i32 {
+      42
+    }
+    pub struct FastCall;
+    impl v8::fast_api::FastFunction for FastCall {
+      fn args(&self) -> &'static [v8::fast_api::Type] {
+        &[v8::fast_api::Type::V8Value]
+      }
+      fn return_type(&self) -> v8::fast_api::CType {
+        v8::fast_api::CType::Int32
+      }
+
+      fn function(&self) -> *const c_void {
+        fast_fn as _
+      }
+    }
+    let template = v8::FunctionTemplate::builder(
+      |scope: &mut v8::HandleScope,
+       _: v8::FunctionCallbackArguments,
+       mut rv: v8::ReturnValue| {
+        rv.set(v8::Integer::new(scope, 42).into());
+      },
+    )
+    .build_fast(scope, &FastCall, None);
+    let name = v8::String::new(scope, "new_fast").unwrap();
+    let value = template.get_function(scope).unwrap();
+
+    global.set(scope, name.into(), value.into()).unwrap();
+  }
+
+  let runs = 100_000_000;
+
+  for x in [
+    "new_",
+    "new_raw",
+    "new_set_uint32",
+    "new_raw_set_uint32",
+    "new_fast",
+  ] {
+    let code = format!(
+      "
+          function bench() {{ return {}(); }};
+          runs = {};
+          start = Date.now();
+          for (i = 0; i < runs; i++) bench();
+          Date.now() - start;
+        ",
+      x, runs
+    );
+
+    let r = eval(scope, &code).unwrap();
+    let number = r.to_number(scope).unwrap();
+    let total_ms = number.number_value(scope).unwrap();
+    let total_ns = 1e6 * total_ms;
+    let ns_per_run = total_ns / (runs as f64);
+    let mops_per_sec = (runs as f64) / (total_ms / 1000.0) / 1e6;
+    println!(
+      "{:.1} ns per run {:.1} million ops/sec → {}",
+      ns_per_run, mops_per_sec, x
+    );
+  }
+}
+
+fn eval<'s>(
+  scope: &mut v8::HandleScope<'s>,
+  code: &str,
+) -> Option<v8::Local<'s, v8::Value>> {
+  let scope = &mut v8::EscapableHandleScope::new(scope);
+  let source = v8::String::new(scope, code).unwrap();
+  let script = v8::Script::compile(scope, source, None).unwrap();
+  let r = script.run(scope);
+  r.map(|v| scope.escape(v))
+}