[ELF] Track line number precisely

`getLineNumber` is both imprecise (when `INCLUDE` is used) and
inefficient (see https://reviews.llvm.org/D104137). Track line number
precisely now that we have `struct Buffer` abstraction from #100493.

Author: MaskRay

lld/ELF/ScriptLexer.cpp

@@ -48,40 +48,14 @@ StringRef ScriptLexer::getLine() {
   return s.substr(0, s.find_first_of("\r\n"));
 }
 
-// Returns 1-based line number of the current token.
-size_t ScriptLexer::getLineNumber() {
-  if (prevTok.empty())
-    return 1;
-  StringRef s = getCurrentMB().getBuffer();
-  const size_t tokOffset = prevTok.data() - s.data();
-
-  // For the first token, or when going backwards, start from the beginning of
-  // the buffer. If this token is after the previous token, start from the
-  // previous token.
-  size_t line = 1;
-  size_t start = 0;
-  if (lastLineNumberOffset > 0 && tokOffset >= lastLineNumberOffset) {
-    start = lastLineNumberOffset;
-    line = lastLineNumber;
-  }
-
-  line += s.substr(start, tokOffset - start).count('\n');
-
-  // Store the line number of this token for reuse.
-  lastLineNumberOffset = tokOffset;
-  lastLineNumber = line;
-
-  return line;
-}
-
 // Returns 0-based column number of the current token.
 size_t ScriptLexer::getColumnNumber() {
   return prevTok.data() - getLine().data();
 }
 
 std::string ScriptLexer::getCurrentLocation() {
   std::string filename = std::string(getCurrentMB().getBufferIdentifier());
-  return (filename + ":" + Twine(getLineNumber())).str();
+  return (filename + ":" + Twine(prevTokLine)).str();
 }
 
 // We don't want to record cascading errors. Keep only the first one.
@@ -177,20 +151,25 @@ StringRef ScriptLexer::skipSpace(StringRef s) {
         setError("unclosed comment in a linker script");
         return "";
       }
+      curBuf.lineNumber += s.substr(0, e).count('\n');
       s = s.substr(e + 2);
       continue;
     }
     if (s.starts_with("#")) {
       size_t e = s.find('\n', 1);
       if (e == StringRef::npos)
         e = s.size() - 1;
+      else
+        ++curBuf.lineNumber;
       s = s.substr(e + 1);
       continue;
     }
-    size_t size = s.size();
+    StringRef saved = s;
     s = s.ltrim();
-    if (s.size() == size)
+    auto len = saved.size() - s.size();
+    if (len == 0)
       return s;
+    curBuf.lineNumber += saved.substr(0, len).count('\n');
   }
 }
 
@@ -199,6 +178,10 @@ bool ScriptLexer::atEOF() { return eof || errorCount(); }
 
 StringRef ScriptLexer::next() {
   prevTok = peek();
+  // `prevTokLine` is not updated for EOF so that the line number in `setError`
+  // will be more useful.
+  if (prevTok.size())
+    prevTokLine = curBuf.lineNumber;
   return std::exchange(curTok, StringRef(curBuf.s.data(), 0));
 }
 

lld/ELF/ScriptLexer.h

@@ -23,6 +23,7 @@ class ScriptLexer {
     // The remaining content to parse and the filename.
     StringRef s, filename;
     const char *begin = nullptr;
+    size_t lineNumber = 1;
     Buffer() = default;
     Buffer(MemoryBufferRef mb)
         : s(mb.getBuffer()), filename(mb.getBufferIdentifier()),
@@ -44,6 +45,7 @@ class ScriptLexer {
   // curTok holds the cached return value of peek() and is invalid when the
   // expression state changes.
   StringRef curTok;
+  size_t prevTokLine = 1;
   // The inExpr state when curTok is cached.
   bool curTokState = false;
   bool eof = false;
@@ -67,12 +69,8 @@ class ScriptLexer {
   std::vector<MemoryBufferRef> mbs;
   bool inExpr = false;
 
-  size_t lastLineNumber = 0;
-  size_t lastLineNumberOffset = 0;
-
 private:
   StringRef getLine();
-  size_t getLineNumber();
   size_t getColumnNumber();
 };
 

lld/test/ELF/linkerscript/overlay.test

@@ -98,5 +98,5 @@ SECTIONS {
   OVERLAY 0x1000 : AT ( 0x2000 ) {
 
 # RUN: not ld.lld a.o -T unclosed.lds 2>&1 | FileCheck %s --check-prefix=UNCLOSED
-# UNCLOSED:     error: unclosed.lds:1: unexpected EOF
+# UNCLOSED:     error: unclosed.lds:2: unexpected EOF
 # UNCLOSED-NOT: {{.}}

lld/test/ELF/linkerscript/sections.s

@@ -103,7 +103,7 @@ SECTIONS {
    .text : { *(.text) }
 
 # RUN: not ld.lld -T unclosed.lds a.o 2>&1 | FileCheck --check-prefix=UNCLOSED %s
-#     UNCLOSED:error: unclosed.lds:1: unexpected EOF
+#     UNCLOSED:error: unclosed.lds:2: unexpected EOF
 # UNCLOSED-NOT:{{.}}
 
 #--- unclosed-out.lds