[lld] Make error handling functions opaque

[MaskRay]

Summary

The inline lld::error expands to two function calls errorHandler and error
where the latter is opaque. Move the functions to .cpp files to decrease code
size.

My x86-64 lld executable is 9KiB smaller.

[thakis]

…do we really care about 9kiB of code? On my system, lld is 49730704 bytes, so that's a 0.2% reduction. Having 7 more lines of code seems worse than the benefit from that win – and that win probably only happens if you build lld without LTO.

But /shrug, if you feel this is a good change, lg I suppose :)

[MaskRay]

In D120002#3329478, @thakis wrote:

…do we really care about 9kiB of code? On my system, lld is 49730704 bytes, so that's a 0.2% reduction. Having 7 more lines of code seems worse than the benefit from that win – and that win probably only happens if you build lld without LTO.

But /shrug, if you feel this is a good change, lg I suppose :)

This saves instruction cache for some hot paths, though it's difficult to measure any improvement.

[MaskRay]

On my system, lld is 49730704 bytes, so that's a 0.2% reduction.

We should count liblld*.a, not every LLVM library pulled in by LTO. Then the ratio will be higher.
(If one compares a non-lld linker with lld, the size of something like LLVMgold.so needs to be counted.)

lld/Common/ErrorHandler.cpp

 void ErrorHandler::flushStreams() {
   std::lock_guard<std::mutex> lock(mu);
   outs().flush();
   errs().flush();
 }
 
 ErrorHandler &lld::errorHandler() { return context().e; }
 
+void lld::error(const Twine &msg) { errorHandler().error(msg); }
+void lld::error(const Twine &msg, ErrorTag tag, ArrayRef<StringRef> args) {
+  errorHandler().error(msg, tag, args);
+}
+void lld::fatal(const Twine &msg) { errorHandler().fatal(msg); }
+void lld::log(const Twine &msg) { errorHandler().log(msg); }
+void lld::message(const Twine &msg, llvm::raw_ostream &s) {
+  errorHandler().message(msg, s);
+}
+void lld::warn(const Twine &msg) { errorHandler().warn(msg); }
+uint64_t lld::errorCount() { return errorHandler().errorCount; }
+
 raw_ostream &lld::outs() {
   ErrorHandler &e = errorHandler();
   return e.outs();
 }
 
 raw_ostream &lld::errs() {
   ErrorHandler &e = errorHandler();
   return e.errs();

lld/include/lld/Common/ErrorHandler.h

private:
   std::mutex mu;
   llvm::raw_ostream *stdoutOS{};
   llvm::raw_ostream *stderrOS{};
 };
 
 /// Returns the default error handler.
 ErrorHandler &errorHandler();
 
-inline void error(const Twine &msg) { errorHandler().error(msg); }
-inline void error(const Twine &msg, ErrorTag tag, ArrayRef<StringRef> args) {
-  errorHandler().error(msg, tag, args);
-}
-[[noreturn]] inline void fatal(const Twine &msg) { errorHandler().fatal(msg); }
-inline void log(const Twine &msg) { errorHandler().log(msg); }
-inline void message(const Twine &msg, llvm::raw_ostream &s = outs()) {
-  errorHandler().message(msg, s);
-}
-inline void warn(const Twine &msg) { errorHandler().warn(msg); }
-inline uint64_t errorCount() { return errorHandler().errorCount; }
+void error(const Twine &msg);
+void error(const Twine &msg, ErrorTag tag, ArrayRef<StringRef> args);
+[[noreturn]] void fatal(const Twine &msg);
+void log(const Twine &msg);
+void message(const Twine &msg, llvm::raw_ostream &s = outs());
+void warn(const Twine &msg);
+uint64_t errorCount();
 
 [[noreturn]] void exitLld(int val);
 
 void diagnosticHandler(const llvm::DiagnosticInfo &di);
 void checkError(Error e);
 
 // check functions are convenient functions to strip errors
 // from error-or-value objects.