[Courgette] Using LabelManager to reduce Courgette-apply peak RAM by 25%.

courgette/encoded_program.h

Index: courgette/encoded_program.h
diff --git a/courgette/encoded_program.h b/courgette/encoded_program.h
index d0ce945f34f9f0db01248516bce99c07b6701d2f..814a45cf35306bb8e3274dc87dec64b3bcdc0e05 100644
--- a/courgette/encoded_program.h
+++ b/courgette/encoded_program.h
@@ -50,10 +50,11 @@ class EncodedProgram {
   // (1) The image base can be specified at any time.
   void set_image_base(uint64_t base) { image_base_ = base; }
 
-  // (2) Address tables and indexes defined first.
-  CheckBool DefineLabels(const RVAToLabel& abs32_labels,
-                         const RVAToLabel& rel32_labels) WARN_UNUSED_RESULT;
+  // (2) Address tables and indexes imported first.
 
+  CheckBool ImportLabels(const LabelManager& abs32_label_manager,
+                         const LabelManager& rel32_label_manager)
+      WARN_UNUSED_RESULT;
 
   // (3) Add instructions in the order needed to generate bytes of file.
   // NOTE: If any of these methods ever fail, the EncodedProgram instance
@@ -114,6 +115,14 @@ class EncodedProgram {
   typedef NoThrowBuffer<OP> OPVector;
 
   void DebuggingSummary();
+
+  // Helper for ImportLabels().
+  static CheckBool WriteRvasToList(const LabelManager& label_manager,
+                                   RvaVector* rvas);
+
+  // Helper for ImportLabels().
+  static void FillUnassignedRvaSlots(RvaVector* rvas);
+
   CheckBool GeneratePeRelocations(SinkStream* buffer,
                                   uint8_t type) WARN_UNUSED_RESULT;
   CheckBool GenerateElfRelocations(Elf32_Word pending_elf_relocation_table,