Windows precompiled header support in GN

tools/gn/ninja_binary_target_writer.h

Index: tools/gn/ninja_binary_target_writer.h
diff --git a/tools/gn/ninja_binary_target_writer.h b/tools/gn/ninja_binary_target_writer.h
index 977e9823fe4fd075949b2f1d9058126cc66ac541..fe7a132c9baa38d9aed9e7c1bbc7d18c4b5cfa0d 100644
--- a/tools/gn/ninja_binary_target_writer.h
+++ b/tools/gn/ninja_binary_target_writer.h
@@ -12,11 +12,14 @@
 #include "tools/gn/unique_vector.h"
 
 struct EscapeOptions;
+class SourceFileTypeSet;
 
 // Writes a .ninja file for a binary target type (an executable, a shared
 // library, or a static library).
 class NinjaBinaryTargetWriter : public NinjaTargetWriter {
  public:
+  class SourceFileTypeSet;
+
   NinjaBinaryTargetWriter(const Target* target, std::ostream& out);
   ~NinjaBinaryTargetWriter() override;
 
@@ -25,9 +28,57 @@ class NinjaBinaryTargetWriter : public NinjaTargetWriter {
  private:
   typedef std::set<OutputFile> OutputFileSet;
 
-  void WriteCompilerVars();
-  void WriteSources(std::vector<OutputFile>* object_files,
+  // Writes all flags for the compiler: includes, defines, cflags, etc.
+  void WriteCompilerVars(const SourceFileTypeSet& used_types);
+
+  // has_precompiled_headers is set when this substitution matches a tool type
+  // that supports precompiled headers, and this target supports precompiled
+  // headers. It doesn't indicate if the tool has precompiled headers (this
+  // will be looked up by this function).
+  //
+  // The tool_type indicates the corresponding tool for flags that are
+  // tool-specific (e.g. "cflags_c"). For non-tool-specific flags (e.g.
+  // "defines") tool_type should be TYPE_NONE.
+  void WriteOneFlag(
+      SubstitutionType subst_enum,
+      bool has_precompiled_headers,
+      Toolchain::ToolType tool_type,
+      const std::vector<std::string>& (ConfigValues::* getter)() const,
+      EscapeOptions flag_escape_options);
+
+  // Writes build lines required for precompiled headers. Any generated
+  // object files will be appended to the given vector.
+  //
+  // input_dep is the stamp file collecting the dependencies required before
+  // compiling this target. It will be empty if there are no input deps.
+  void WritePrecompiledHeaderCommands(const SourceFileTypeSet& used_types,
+                                      const OutputFile& input_dep,
+                                      std::vector<OutputFile>* object_files);
+
+  // Writes a Windows .pch compile build line for a language type.
+  void WriteWindowsPCHCommand(SubstitutionType flag_type,
+                              Toolchain::ToolType tool_type,
+                              const OutputFile& input_dep,
+                              std::vector<OutputFile>* object_files);
+
+  // extra_deps are additional dependencies to run before the rule.
+  //
+  // iorder_only_dep is the name of the stamp file that covers the dependencies
+  // that must be run before doing any compiles.
+  //
+  // The files produced by the compiler will be added to two output vectors.
+  void WriteSources(const std::vector<OutputFile>& extra_deps,
+                    const OutputFile& order_only_dep,
+                    std::vector<OutputFile>* object_files,
                     std::vector<SourceFile>* other_files);
+
+  // Writes a build line.
+  void WriteCompilerBuildLine(const SourceFile& source,
+                              const std::vector<OutputFile>& extra_deps,
+                              const OutputFile& order_only_dep,
+                              Toolchain::ToolType tool_type,
+                              const std::vector<OutputFile>& outputs);
+
   void WriteLinkerStuff(const std::vector<OutputFile>& object_files,
                         const std::vector<SourceFile>& other_files);
   void WriteLinkerFlags(const SourceFile* optional_def_file);
@@ -61,25 +112,15 @@ class NinjaBinaryTargetWriter : public NinjaTargetWriter {
   void WriteOrderOnlyDependencies(
       const UniqueVector<const Target*>& non_linkable_deps);
 
-  // Computes the set of output files resulting from compiling the given source
-  // file. If the file can be compiled and the tool exists, fills the outputs in
-  // and writes the tool type to computed_tool_type. If the file is not
-  // compilable, returns false.
-  //
-  // The target that the source belongs to is passed as an argument. In the
-  // case of linking to source sets, this can be different than the target
-  // this class is currently writing.
-  //
-  // The function can succeed with a "NONE" tool type for object files which are
-  // just passed to the output. The output will always be overwritten, not
-  // appended to.
-  bool GetOutputFilesForSource(const Target* target,
-                               const SourceFile& source,
-                               Toolchain::ToolType* computed_tool_type,
-                               std::vector<OutputFile>* outputs) const;
+  // Returns the computed name of the Windows .pch file for the given
+  // tool type. The tool must support precompiled headers.
+  OutputFile GetWindowsPCHFile(Toolchain::ToolType tool_type) const;
 
   const Tool* tool_;
 
+  // Cached version of the prefix used for rule types for this toolchain.
+  std::string rule_prefix_;
+
   DISALLOW_COPY_AND_ASSIGN(NinjaBinaryTargetWriter);
 };