Updated comments based on feedback

Clarified entry points comments. Added formatting detection.

Author: mxswd

include/swift/Frontend/FrontendOptions.h

@@ -231,7 +231,11 @@ class FrontendOptions {
   /// Indicates whether the playground transformation should be applied.
   bool PlaygroundTransform = false;
 
-  /// Indicates whether the pc macro should be applied.
+  /// Indicates whether the AST should be instrumented to simulate a debugger's
+  /// program counter. Similar to the PlaygroundTransform, this will instrument
+  /// the AST with function calls that get called when you would see a program
+  /// counter move in a debugger. To adopt this implement the
+  /// __builtin_pc_before and __builtin_pc_after functions.
   bool PCMacro = false;
 
   /// Indicates whether the playground transformation should omit

include/swift/Subsystems.h

@@ -153,9 +153,9 @@ namespace swift {
   /// instrumentation that has a high runtime performance impact.
   void performPlaygroundTransform(SourceFile &SF, bool HighPerformance);
 
-  /// Once parsing, name-binding and the playground transform (if required)
-  /// are complete this optionally walks the ASTs to add calls to externally
-  /// provided functions that simulate "program counter"-like debugging events.
+  /// Once parsing and name-binding are complete this optionally walks the ASTs
+  /// to add calls to externally provided functions that simulate
+  /// "program counter"-like debugging events.
   void performPCMacro(SourceFile &SF, TopLevelContext &TLC);
 
   /// Flags used to control type checking.

lib/Sema/InstrumenterSupport.h

@@ -1,4 +1,4 @@
-//===--- InstrumenterSupport.h - Instrumenter Support ---------------------===//
+//===--- InstrumenterSupport.h - Instrumenter Support -----------*- C++ -*-===//
 //
 // This source file is part of the Swift.org open source project
 //