[flang] Add __COUNTER__ preprocessor macro

Author: N00byKing

flang/include/flang/Parser/preprocessor.h

@@ -121,6 +121,8 @@ class Preprocessor {
   std::list<std::string> names_;
   std::unordered_map<CharBlock, Definition> definitions_;
   std::stack<CanDeadElseAppear> ifStack_;
+
+  unsigned int counter_val_{0};
 };
 } // namespace Fortran::parser
 #endif // FORTRAN_PARSER_PREPROCESSOR_H_

flang/lib/Parser/preprocessor.cpp

@@ -22,6 +22,7 @@
 #include <memory>
 #include <optional>
 #include <set>
+#include <string>
 #include <utility>
 #include <vector>
 
@@ -299,6 +300,7 @@ void Preprocessor::DefineStandardMacros() {
   Define("__FILE__"s, "__FILE__"s);
   Define("__LINE__"s, "__LINE__"s);
   Define("__TIMESTAMP__"s, "__TIMESTAMP__"s);
+  Define("__COUNTER__"s, "__COUNTER__"s);
 }
 
 void Preprocessor::Define(const std::string &macro, const std::string &value) {
@@ -421,6 +423,8 @@ std::optional<TokenSequence> Preprocessor::MacroReplacement(
               repl = "\""s + time + '"';
             }
           }
+        } else if (name == "__COUNTER__") {
+          repl = std::to_string(counter_val_++);
         }
         if (!repl.empty()) {
           ProvenanceRange insert{allSources_.AddCompilerInsertion(repl)};

flang/test/Preprocessing/counter.F90

@@ -0,0 +1,9 @@
+! RUN: %flang -E %s | FileCheck %s
+! CHECK: print *, 0
+! CHECK: print *, 1
+! CHECK: print *, 2
+! Check incremental counter macro
+#define foo bar
+print *, __COUNTER__
+print *, __COUNTER__
+print *, __COUNTER__