[llc] Support -time-trace in llc

[aeubanks]

Summary

Mostly copied from opt.cpp.

[hans]

lgtm

llvm/test/tools/llc/time-trace.ll

+; RUN: llc -o /dev/null -O2 -time-trace -time-trace-granularity=100 -time-trace-file=%t.json
+; RUN: FileCheck --input-file=%t.json %s
+
+; CHECK: "traceEvents"
+
+define void @f() {
+  ret void
+}

llvm/tools/llc/llc.cpp

 //===-- llc.cpp - Implement the LLVM Native Code Generator ----------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This is the llc code generator driver. It provides a convenient
 // command-line interface for generating native assembly-language code
 // or C code, given LLVM bitcode.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/ScopeExit.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/CodeGen/CommandFlags.h"
 #include "llvm/CodeGen/LinkAllAsmWriterComponents.h"
 #include "llvm/CodeGen/LinkAllCodegenComponents.h"
 #include "llvm/CodeGen/MIRParser/MIRParser.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/MachineModuleInfo.h"

 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/FormattedStream.h"
 #include "llvm/Support/Host.h"
 #include "llvm/Support/InitLLVM.h"
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/PluginLoader.h"
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/TargetSelect.h"
+#include "llvm/Support/TimeProfiler.h"
 #include "llvm/Support/ToolOutputFile.h"
 #include "llvm/Support/WithColor.h"
 #include "llvm/Target/TargetLoweringObjectFile.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Transforms/Utils/Cloning.h"
 #include <memory>
 using namespace llvm;
 
SplitDwarfOutputFile("split-dwarf-output",
                          cl::desc(".dwo output filename"),
                          cl::value_desc("filename"));
 
 static cl::opt<unsigned>
 TimeCompilations("time-compilations", cl::Hidden, cl::init(1u),
                  cl::value_desc("N"),
                  cl::desc("Repeat compilation N times for timing"));
 
+static cl::opt<bool> TimeTrace("time-trace", cl::desc("Record time trace"));
+
+static cl::opt<unsigned> TimeTraceGranularity(
+    "time-trace-granularity",
+    cl::desc(
+        "Minimum time granularity (in microseconds) traced by time profiler"),
+    cl::init(500), cl::Hidden);
+
+static cl::opt<std::string>
+    TimeTraceFile("time-trace-file",
+                  cl::desc("Specify time trace file destination"),
+                  cl::value_desc("filename"));
+
 static cl::opt<std::string>
     BinutilsVersion("binutils-version", cl::Hidden,
                     cl::desc("Produced object files can use all ELF features "
                              "supported by this binutils version and newer."
                              "If -no-integrated-as is specified, the generated "
                              "assembly will consider GNU as support."
                              "'none' means that all ELF features can be used, "
                              "regardless of binutils support"));
int main(int argc, char **argv) {
   // Initialize debugging passes.
   initializeScavengerTestPass(*Registry);
 
   // Register the target printer for --version.
   cl::AddExtraVersionPrinter(TargetRegistry::printRegisteredTargetsForVersion);
 
   cl::ParseCommandLineOptions(argc, argv, "llvm system compiler\n");
 
+  if (TimeTrace)
+    timeTraceProfilerInitialize(TimeTraceGranularity, argv[0]);
+  auto TimeTraceScopeExit = make_scope_exit([]() {
+    if (TimeTrace) {
+      if (auto E = timeTraceProfilerWrite(TimeTraceFile, OutputFilename)) {
+        handleAllErrors(std::move(E), [&](const StringError &SE) {
+          errs() << SE.getMessage() << "\n";
+        });
+        return;
+      }
+      timeTraceProfilerCleanup();
+    }
+  });
+
   LLVMContext Context;
   Context.setDiscardValueNames(DiscardValueNames);
 
   // Set a diagnostic handler that doesn't exit on the first error
   bool HasError = false;
   Context.setDiagnosticHandler(
       std::make_unique<LLCDiagnosticHandler>(&HasError));