[Core] Add flag to check if RoundTripPasses need to be run.

This would allow other flavor specific contexts to override the default value,
if they want to optionally run the round trip passes.

There is some information lost like the original file owner of the atom with
RoundTripPasses. The Gnu flavor needs this information inorder to implement
LinkerScript matching and for other diagnostic outputs such as Map files.

The flag also can be used to record information in the Atom if the information
to the Writer needs to be conveyed through References too.

llvm-svn: 222983

lld/include/lld/Core/LinkingContext.h

@@ -318,8 +318,15 @@ public:
   /// Return the next ordinal and Increment it.
   virtual uint64_t getNextOrdinalAndIncrement() const { return _nextOrdinal++; }
 
-  /// @}
+#ifndef NDEBUG
+  void setRunRoundTripPass(bool roundTripPass) {
+    _runRoundTripPasses = roundTripPass;
+  }
 
+  bool runRoundTripPass() const { return _runRoundTripPasses; }
+#endif
+
+  /// @}
 protected:
   LinkingContext(); // Must be subclassed
 
@@ -350,6 +357,9 @@ protected:
   bool _allowRemainingUndefines;
   bool _logInputFiles;
   bool _allowShlibUndefines;
+#ifndef NDEBUG
+  bool _runRoundTripPasses;
+#endif
   OutputFileType _outputFileType;
   std::vector<StringRef> _deadStripRoots;
   std::map<std::string, std::string> _aliasSymbols;

lld/lib/Core/LinkingContext.cpp

@@ -13,9 +13,28 @@
 #include "lld/Core/Simple.h"
 #include "lld/ReaderWriter/Writer.h"
 #include "llvm/ADT/Triple.h"
+#include "llvm/Support/Process.h"
 
 namespace lld {
 
+#ifndef NDEBUG
+LinkingContext::LinkingContext()
+    : _deadStrip(false), _allowDuplicates(false),
+      _globalsAreDeadStripRoots(false),
+      _searchArchivesToOverrideTentativeDefinitions(false),
+      _searchSharedLibrariesToOverrideTentativeDefinitions(false),
+      _warnIfCoalesableAtomsHaveDifferentCanBeNull(false),
+      _warnIfCoalesableAtomsHaveDifferentLoadName(false),
+      _printRemainingUndefines(true), _allowRemainingUndefines(false),
+      _logInputFiles(false), _allowShlibUndefines(false),
+      _runRoundTripPasses(false), _outputFileType(OutputFileType::Default),
+      _nextOrdinal(0) {
+  llvm::Optional<std::string> env =
+      llvm::sys::Process::GetEnv("LLD_RUN_ROUNDTRIP_TEST");
+  if (env.hasValue() && !env.getValue().empty())
+    setRunRoundTripPass(true);
+}
+#else
 LinkingContext::LinkingContext()
     : _deadStrip(false), _allowDuplicates(false),
       _globalsAreDeadStripRoots(false),
@@ -26,6 +45,7 @@ LinkingContext::LinkingContext()
       _printRemainingUndefines(true), _allowRemainingUndefines(false),
       _logInputFiles(false), _allowShlibUndefines(false),
       _outputFileType(OutputFileType::Default), _nextOrdinal(0) {}
+#endif
 
 LinkingContext::~LinkingContext() {}
 

lld/lib/Driver/Driver.cpp

@@ -23,7 +23,6 @@
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"
-#include "llvm/Support/Process.h"
 #include "llvm/Support/raw_ostream.h"
 #include <mutex>
 
@@ -114,8 +113,7 @@ bool Driver::link(LinkingContext &context, raw_ostream &diagnostics) {
   context.addPasses(pm);
 
 #ifndef NDEBUG
-  llvm::Optional<std::string> env = llvm::sys::Process::GetEnv("LLD_RUN_ROUNDTRIP_TEST");
-  if (env.hasValue() && !env.getValue().empty()) {
+  if (context.runRoundTripPass()) {
     pm.add(std::unique_ptr<Pass>(new RoundTripYAMLPass(context)));
     pm.add(std::unique_ptr<Pass>(new RoundTripNativePass(context)));
   }