[gold] Enable time trace profiler in LLVMgold (#94293)

To get the time trace of LTO in the gold plugin, now we can pass the
`time-trace=<time trace file>` as well as
`time-trace-granularity=<granularity>` flags to LLVMgold.

Note that we still have to populate `LTOConfig::TimeTraceEnabled` and
`LTOConfig::TimeTraceGranularity` because ThinLTO backend needs them.

llvm/test/tools/gold/X86/time-trace.ll

@@ -0,0 +1,32 @@
+; RUN: llvm-as %s -o %t.o
+
+; RUN: %gold -plugin %llvmshlibdir/LLVMgold%shlibext \
+; RUN:    -m elf_x86_64 --plugin-opt=time-trace=%t2.json \
+; RUN:    -shared %t.o -o /dev/null
+; RUN: FileCheck --input-file %t2.json %s
+
+; RUN: %gold -plugin %llvmshlibdir/LLVMgold%shlibext \
+; RUN:    -m elf_x86_64 --plugin-opt=time-trace=%t2.json \
+; RUN:    --plugin-opt=time-trace-granularity=250  \
+; RUN:    -shared %t.o -o /dev/null
+; RUN: FileCheck --input-file %t2.json %s
+
+; RUN: not %gold -plugin %llvmshlibdir/LLVMgold%shlibext \
+; RUN:    -m elf_x86_64 --plugin-opt=time-trace=%t2.json \
+; RUN:    --plugin-opt=time-trace-granularity=hello  \
+; RUN:    -shared %t.o -o /dev/null 2> %t4.txt
+; RUN: FileCheck --input-file %t4.txt %s --check-prefix=ERR
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @f1() {
+  ret void
+}
+
+define void @f2() {
+  ret void
+}
+
+; CHECK: "traceEvents":
+; ERR: Invalid time trace granularity: hello

llvm/tools/gold/gold-plugin.cpp

@@ -11,6 +11,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/ADT/ScopeExit.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Bitcode/BitcodeReader.h"
 #include "llvm/Bitcode/BitcodeWriter.h"
@@ -31,6 +32,7 @@
 #include "llvm/Support/Path.h"
 #include "llvm/Support/TargetSelect.h"
 #include "llvm/Support/Threading.h"
+#include "llvm/Support/TimeProfiler.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/TargetParser/Host.h"
 #include <list>
@@ -220,6 +222,10 @@ namespace options {
   static std::string cs_profile_path;
   static bool cs_pgo_gen = false;
 
+  // Time trace options.
+  static std::string time_trace_file;
+  static unsigned time_trace_granularity = 500;
+
   static void process_plugin_option(const char *opt_)
   {
     if (opt_ == nullptr)
@@ -308,6 +314,14 @@ namespace options {
       RemarksFormat = std::string(opt);
     } else if (opt.consume_front("stats-file=")) {
       stats_file = std::string(opt);
+    } else if (opt.consume_front("time-trace=")) {
+      time_trace_file = std::string(opt);
+    } else if (opt.consume_front("time-trace-granularity=")) {
+      unsigned Granularity;
+      if (opt.getAsInteger(10, Granularity))
+        message(LDPL_FATAL, "Invalid time trace granularity: %s", opt);
+      else
+        time_trace_granularity = Granularity;
     } else {
       // Save this option to pass to the code generator.
       // ParseCommandLineOptions() expects argv[0] to be program name. Lazily
@@ -953,6 +967,10 @@ static std::unique_ptr<LTO> createLTO(IndexWriteCallback OnIndexWrite,
   Conf.HasWholeProgramVisibility = options::whole_program_visibility;
 
   Conf.StatsFile = options::stats_file;
+
+  Conf.TimeTraceEnabled = !options::time_trace_file.empty();
+  Conf.TimeTraceGranularity = options::time_trace_granularity;
+
   return std::make_unique<LTO>(std::move(Conf), Backend,
                                 options::ParallelCodeGenParallelismLevel);
 }
@@ -1113,6 +1131,19 @@ static ld_plugin_status allSymbolsReadHook() {
   if (unsigned NumOpts = options::extra.size())
     cl::ParseCommandLineOptions(NumOpts, &options::extra[0]);
 
+  // Initialize time trace profiler
+  if (!options::time_trace_file.empty())
+    llvm::timeTraceProfilerInitialize(options::time_trace_granularity,
+                                      options::extra.size() ? options::extra[0]
+                                                            : "LLVMgold");
+  auto FinalizeTimeTrace = llvm::make_scope_exit([&]() {
+    if (!llvm::timeTraceProfilerEnabled())
+      return;
+    assert(!options::time_trace_file.empty());
+    check(llvm::timeTraceProfilerWrite(options::time_trace_file, output_name));
+    llvm::timeTraceProfilerCleanup();
+  });
+
   std::vector<std::pair<SmallString<128>, bool>> Files = runLTO();
 
   if (options::TheOutputType == options::OT_DISABLE ||