[flang] Clean out some dead code, improve naming & comments

Original-commit: flang-compiler/f18@3495555565
Reviewed-on: https://github.com/flang-compiler/f18/pull/715
Tree-same-pre-rewrite: false

flang/CMakeLists.txt

@@ -97,7 +97,6 @@ if(CMAKE_COMPILER_IS_GNUCXX OR (CMAKE_CXX_COMPILER_ID MATCHES "Clang"))
    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wcast-qual")
    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wimplicit-fallthrough")
    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wdelete-non-virtual-dtor")
-   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-unused-command-line-argument")
    set(CMAKE_CXX_FLAGS_RELEASE    "-O2")
    set(CMAKE_CXX_FLAGS_MINSIZEREL "-O2 '-DCHECK=(void)'")
    set(CMAKE_CXX_FLAGS_DEBUG      "-g -DDEBUGF18")

flang/lib/parser/char-buffer.h

@@ -44,7 +44,7 @@ public:
   }
 
   bool empty() const { return bytes_ == 0; }
-  std::size_t size() const { return bytes_; }
+  std::size_t bytes() const { return bytes_; }
 
   void clear() {
     blocks_.clear();

flang/lib/parser/provenance.cc

@@ -28,12 +28,13 @@ void OffsetToProvenanceMappings::shrink_to_fit() {
   provenanceMap_.shrink_to_fit();
 }
 
-std::size_t OffsetToProvenanceMappings::size() const {
+std::size_t OffsetToProvenanceMappings::SizeInBytes() const {
   if (provenanceMap_.empty()) {
     return 0;
+  } else {
+    const ContiguousProvenanceMapping &last{provenanceMap_.back()};
+    return last.start + last.range.size();
   }
-  const ContiguousProvenanceMapping &last{provenanceMap_.back()};
-  return last.start + last.range.size();
 }
 
 void OffsetToProvenanceMappings::Put(ProvenanceRange range) {
@@ -241,14 +242,6 @@ const SourceFile *AllSources::GetSourceFile(
       origin.u);
 }
 
-ProvenanceRange AllSources::GetContiguousRangeAround(
-    ProvenanceRange range) const {
-  CHECK(IsValid(range));
-  const Origin &origin{MapToOrigin(range.start())};
-  CHECK(origin.covers.Contains(range));
-  return origin.covers;
-}
-
 std::string AllSources::GetPath(Provenance at) const {
   const SourceFile *source{GetSourceFile(at)};
   return source ? source->path() : ""s;
@@ -329,7 +322,7 @@ std::optional<ProvenanceRange> CookedSource::GetProvenanceRange(
 }
 
 void CookedSource::Marshal() {
-  CHECK(provenanceMap_.size() == buffer_.size());
+  CHECK(provenanceMap_.SizeInBytes() == buffer_.bytes());
   provenanceMap_.Put(allSources_.AddCompilerInsertion("(after end of source)"));
   data_ = buffer_.Marshal();
   buffer_.clear();

flang/lib/parser/provenance.h

@@ -90,10 +90,10 @@ using ProvenanceRange = common::Interval<Provenance>;
 class OffsetToProvenanceMappings {
 public:
   OffsetToProvenanceMappings() {}
-  std::size_t size() const;
   void clear();
   void swap(OffsetToProvenanceMappings &);
   void shrink_to_fit();
+  std::size_t SizeInBytes() const;
   void Put(ProvenanceRange);
   void Put(const OffsetToProvenanceMappings &);
   ProvenanceRange Map(std::size_t at) const;
@@ -106,6 +106,8 @@ private:
     ProvenanceRange range;
   };
 
+  // Elements appear in ascending order of distinct .start values;
+  // their .range values are disjoint and not necessarily adjacent.
   std::vector<ContiguousProvenanceMapping> provenanceMap_;
 };
 
@@ -143,7 +145,6 @@ public:
       const std::string &message, bool echoSourceLine = false) const;
   const SourceFile *GetSourceFile(
       Provenance, std::size_t *offset = nullptr) const;
-  ProvenanceRange GetContiguousRangeAround(ProvenanceRange) const;
   std::string GetPath(Provenance) const;  // __FILE__
   int GetLineNumber(Provenance) const;  // __LINE__
   Provenance CompilerInsertionProvenance(char ch);
@@ -155,9 +156,6 @@ private:
     const SourceFile &source;
     bool isModule{false};
   };
-  struct Module {
-    const SourceFile &source;
-  };
   struct Macro {
     ProvenanceRange definition;
     std::string expansion;
@@ -182,6 +180,7 @@ private:
 
   const Origin &MapToOrigin(Provenance) const;
 
+  // Elements are in ascending & contiguous order of .covers.
   std::vector<Origin> origin_;
   ProvenanceRange range_;
   std::map<char, Provenance> compilerInsertionProvenance_;

flang/lib/parser/source.cc

@@ -223,7 +223,7 @@ bool SourceFile::ReadFile(std::string errorPath, std::stringstream *error) {
     --openFileDescriptors;
   }
   fileDescriptor_ = -1;
-  if (buffer.size() == 0) {
+  if (buffer.bytes() == 0) {
     // empty file
     address_ = content_ = nullptr;
     size_ = bytes_ = 0;