add cpuprofile to ra_prof

Now, one can use `let _p = ra_prof::cpu_profiler()` to capture profile
of a block of code.

This is not an out of the box experience, as that relies on gperfools

See the docs on https://github.com/AtheMathmo/cpuprofiler for more!

Author: matklad

Cargo.lock

@@ -15,5 +15,9 @@ ra_ide_api = { path = "../ra_ide_api" }
 ra_hir = { path = "../ra_hir" }
 ra_project_model = { path = "../ra_project_model" }
 
+[dependencies.ra_prof]
+path = "../ra_prof"
+# features = [ "cpuprofiler" ]
+
 [dev-dependencies]
 test_utils = { path = "../test_utils" }

crates/ra_batch/Cargo.toml

@@ -9,3 +9,4 @@ publish = false
 once_cell = "0.2.0"
 itertools = "0.8.0"
 backtrace = "0.3.28"
+cpuprofiler = { version = "0.0.3", optional = true }

crates/ra_prof/Cargo.toml

@@ -255,6 +255,39 @@ impl Drop for Scope {
     }
 }
 
+/// A wrapper around https://github.com/AtheMathmo/cpuprofiler
+///
+/// It can be used to capture sampling profiles of sections of code.
+/// It is not exactly out-of-the-box, as it relies on gperftools.
+/// See the docs for the crate for more!
+#[derive(Debug)]
+pub struct CpuProfiler {
+    _private: (),
+}
+
+pub fn cpu_profiler() -> CpuProfiler {
+    #[cfg(feature = "cpuprofiler")]
+    {
+        cpuprofiler::PROFILER.lock().unwrap().start("./out.profile").unwrap();
+    }
+
+    #[cfg(not(feature = "cpuprofiler"))]
+    {
+        eprintln!("cpuprofiler feature is disabled")
+    }
+
+    CpuProfiler { _private: () }
+}
+
+impl Drop for CpuProfiler {
+    fn drop(&mut self) {
+        #[cfg(feature = "cpuprofiler")]
+        {
+            cpuprofiler::PROFILER.lock().unwrap().stop().unwrap();
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;