Do not call StmtProfile::set_codemap twice per function call

Summary:
Do not call `self.stmt_profile.set_codemap(codemap)` in `Evaluator::set_codemap`.

Although `StmtProfile::set_codemap` is cheap, `Evaluator::set_codemap` is called twice per function call.

Reviewed By: ndmitchell

Differential Revision: D30872419

fbshipit-source-id: ee63849c92c44c30b626ea556e37ba2d7b5c155a

Author: stepancheg

starlark/src/eval/runtime/evaluator.rs

@@ -189,7 +189,7 @@ impl<'v, 'a> Evaluator<'v, 'a> {
     /// See [`Evaluator::enable_heap_profile`] for details about the types of Starlark profiles.
     pub fn enable_stmt_profile(&mut self) {
         self.stmt_profile.enable();
-        self.before_stmt(&|span, eval| eval.stmt_profile.before_stmt(span));
+        self.before_stmt(&|span, eval| eval.stmt_profile.before_stmt(span, eval.codemap));
     }
 
     /// Enable statement profiling, allowing [`Evaluator::write_flame_profile`] to be used.
@@ -304,7 +304,6 @@ impl<'v, 'a> Evaluator<'v, 'a> {
     }
 
     pub(crate) fn set_codemap(&mut self, codemap: &'v CodeMap) -> &'v CodeMap {
-        self.stmt_profile.set_codemap(codemap);
         mem::replace(&mut self.codemap, codemap)
     }
 

starlark/src/eval/runtime/stmt_profile.rs

@@ -82,14 +82,17 @@ impl StmtProfileData {
         }
     }
 
-    fn before_stmt(&mut self, span: Span) {
+    fn before_stmt(&mut self, span: Span, codemap: &CodeMap) {
         let now = Instant::now();
         self.add_last(now);
+        if self.last_span.0 != FileId::new(codemap) {
+            self.add_codemap(codemap);
+        }
         self.last_span = (self.next_file, span);
         self.last_start = now;
     }
 
-    fn set_codemap(&mut self, codemap: &CodeMap) {
+    fn add_codemap(&mut self, codemap: &CodeMap) {
         let id = FileId::new(codemap);
         self.next_file = id;
         match self.files.entry(id) {
@@ -179,15 +182,9 @@ impl StmtProfile {
         self.0 = Some(box StmtProfileData::new())
     }
 
-    pub fn before_stmt(&mut self, span: Span) {
-        if let Some(box data) = &mut self.0 {
-            data.before_stmt(span)
-        }
-    }
-
-    pub fn set_codemap(&mut self, codemap: &CodeMap) {
+    pub fn before_stmt(&mut self, span: Span, codemap: &CodeMap) {
         if let Some(box data) = &mut self.0 {
-            data.set_codemap(codemap)
+            data.before_stmt(span, codemap)
         }
     }