[clang][Diagnostics][NFC] Merge byte/column mapping functions into one.

They were both only called from one place and did very similar things.
Merge them into one, so we only have to iterate the source line once to
generate the SourceMap.

Differential Revision: https://reviews.llvm.org/D151100

clang/lib/Frontend/TextDiagnostic.cpp

@@ -173,7 +173,21 @@ static void expandTabs(std::string &SourceLine, unsigned TabStop) {
   }
 }
 
-/// This function takes a raw source line and produces a mapping from the bytes
+/// \p BytesOut:
+///  A mapping from columns to the byte of the source line that produced the
+///  character displaying at that column. This is the inverse of \p ColumnsOut.
+///
+/// The last element in the array is the number of bytes in the source string.
+///
+/// example: (given a tabstop of 8)
+///
+///    "a \t \u3042" -> {0,1,2,-1,-1,-1,-1,-1,3,4,-1,7}
+///
+///  (\\u3042 is represented in UTF-8 by three bytes and takes two columns to
+///   display)
+///
+/// \p ColumnsOut:
+///  A mapping from the bytes
 ///  of the printable representation of the line to the columns those printable
 ///  characters will appear at (numbering the first column as 0).
 ///
@@ -195,69 +209,42 @@ static void expandTabs(std::string &SourceLine, unsigned TabStop) {
 ///
 ///  (\\u3042 is represented in UTF-8 by three bytes and takes two columns to
 ///   display)
-static void byteToColumn(StringRef SourceLine, unsigned TabStop,
-                         SmallVectorImpl<int> &out) {
-  out.clear();
+static void genColumnByteMapping(StringRef SourceLine, unsigned TabStop,
+                                 SmallVectorImpl<int> &BytesOut,
+                                 SmallVectorImpl<int> &ColumnsOut) {
+  assert(BytesOut.empty());
+  assert(ColumnsOut.empty());
 
   if (SourceLine.empty()) {
-    out.resize(1u,0);
+    BytesOut.resize(1u, 0);
+    ColumnsOut.resize(1u, 0);
     return;
   }
 
-  out.resize(SourceLine.size()+1, -1);
-
-  int columns = 0;
-  size_t i = 0;
-  while (i<SourceLine.size()) {
-    out[i] = columns;
-    std::pair<SmallString<16>,bool> res
-      = printableTextForNextCharacter(SourceLine, &i, TabStop);
-    columns += llvm::sys::locale::columnWidth(res.first);
-  }
-  out.back() = columns;
-}
-
-/// This function takes a raw source line and produces a mapping from columns
-///  to the byte of the source line that produced the character displaying at
-///  that column. This is the inverse of the mapping produced by byteToColumn()
-///
-/// The last element in the array is the number of bytes in the source string
-///
-/// example: (given a tabstop of 8)
-///
-///    "a \t \u3042" -> {0,1,2,-1,-1,-1,-1,-1,3,4,-1,7}
-///
-///  (\\u3042 is represented in UTF-8 by three bytes and takes two columns to
-///   display)
-static void columnToByte(StringRef SourceLine, unsigned TabStop,
-                         SmallVectorImpl<int> &out) {
-  out.clear();
+  ColumnsOut.resize(SourceLine.size() + 1, -1);
 
-  if (SourceLine.empty()) {
-    out.resize(1u, 0);
-    return;
+  int Columns = 0;
+  size_t I = 0;
+  while (I < SourceLine.size()) {
+    ColumnsOut[I] = Columns;
+    BytesOut.resize(Columns + 1, -1);
+    BytesOut.back() = I;
+    auto [Str, Printable] =
+        printableTextForNextCharacter(SourceLine, &I, TabStop);
+    Columns += llvm::sys::locale::columnWidth(Str);
   }
 
-  int columns = 0;
-  size_t i = 0;
-  while (i<SourceLine.size()) {
-    out.resize(columns+1, -1);
-    out.back() = i;
-    std::pair<SmallString<16>,bool> res
-      = printableTextForNextCharacter(SourceLine, &i, TabStop);
-    columns += llvm::sys::locale::columnWidth(res.first);
-  }
-  out.resize(columns+1, -1);
-  out.back() = i;
+  ColumnsOut.back() = Columns;
+  BytesOut.resize(Columns + 1, -1);
+  BytesOut.back() = I;
 }
 
 namespace {
 struct SourceColumnMap {
   SourceColumnMap(StringRef SourceLine, unsigned TabStop)
   : m_SourceLine(SourceLine) {
 
-    ::byteToColumn(SourceLine, TabStop, m_byteToColumn);
-    ::columnToByte(SourceLine, TabStop, m_columnToByte);
+    genColumnByteMapping(SourceLine, TabStop, m_columnToByte, m_byteToColumn);
 
     assert(m_byteToColumn.size()==SourceLine.size()+1);
     assert(0 < m_byteToColumn.size() && 0 < m_columnToByte.size());