[LTO] Add plumbing to save stats during LTO on Darwin.

Gold and ld on Linux already support saving stats, but the
infrastructure is missing on Darwin. Unfortunately it seems like the
configuration from lib/LTO/LTO.cpp is not used.

This patch adds a new LTOStatsFile option and adds plumbing in Clang to
use it on Darwin, similar to the way remarks are handled.

Currnetly the handling of LTO flags seems quite spread out, with a bunch
of duplication. But I am not sure if there is an easy way to improve
that?

Reviewers: anemet, tejohnson, thegameg, steven_wu

Reviewed By: steven_wu

Differential Revision: https://reviews.llvm.org/D60516

llvm-svn: 358753

4 files changed, 46 insertions, 13 deletions

diff --git a/llvm/include/llvm/LTO/LTO.h b/llvm/include/llvm/LTO/LTO.h
index 24e80fbd09e..8fcf1075721 100644
--- a/llvm/include/llvm/LTO/LTO.h
+++ b/llvm/include/llvm/LTO/LTO.h
@@ -87,6 +87,10 @@ setupOptimizationRemarks(LLVMContext &Context, StringRef LTORemarksFilename,
                          StringRef LTORemarksPasses,
                          bool LTOPassRemarksWithHotness, int Count = -1);
 
+/// Setups the output file for saving statistics.
+Expected<std::unique_ptr<ToolOutputFile>>
+setupStatsFile(StringRef StatsFilename);
+
 class LTO;
 struct SymbolResolution;
 class ThinBackendProc;
diff --git a/llvm/include/llvm/LTO/legacy/LTOCodeGenerator.h b/llvm/include/llvm/LTO/legacy/LTOCodeGenerator.h
index 37fef191a28..d3cb4c8b79a 100644
--- a/llvm/include/llvm/LTO/legacy/LTOCodeGenerator.h
+++ b/llvm/include/llvm/LTO/legacy/LTOCodeGenerator.h
@@ -241,6 +241,7 @@ private:
   TargetMachine::CodeGenFileType FileType = TargetMachine::CGFT_ObjectFile;
   std::unique_ptr<ToolOutputFile> DiagnosticOutputFile;
   bool Freestanding = false;
+  std::unique_ptr<ToolOutputFile> StatsFile = nullptr;
 };
 }
 #endif
diff --git a/llvm/lib/LTO/LTO.cpp b/llvm/lib/LTO/LTO.cpp
index 1accbf40b96..ab5b78071c6 100644
--- a/llvm/lib/LTO/LTO.cpp
+++ b/llvm/lib/LTO/LTO.cpp
@@ -885,16 +885,10 @@ Error LTO::run(AddStreamFn AddStream, NativeObjectCache Cache) {
                                   isPrevailing, Conf.OptLevel > 0);
 
   // Setup output file to emit statistics.
-  std::unique_ptr<ToolOutputFile> StatsFile = nullptr;
-  if (!Conf.StatsFile.empty()) {
-    EnableStatistics(false);
-    std::error_code EC;
-    StatsFile =
-        llvm::make_unique<ToolOutputFile>(Conf.StatsFile, EC, sys::fs::F_None);
-    if (EC)
-      return errorCodeToError(EC);
-    StatsFile->keep();
-  }
+  auto StatsFileOrErr = setupStatsFile(Conf.StatsFile);
+  if (!StatsFileOrErr)
+    return StatsFileOrErr.takeError();
+  std::unique_ptr<ToolOutputFile> StatsFile = std::move(StatsFileOrErr.get());
 
   // Finalize linking of regular LTO modules containing summaries now that
   // we have computed liveness information.
@@ -1343,3 +1337,20 @@ lto::setupOptimizationRemarks(LLVMContext &Context,
   DiagnosticFile->keep();
   return std::move(DiagnosticFile);
 }
+
+Expected<std::unique_ptr<ToolOutputFile>>
+lto::setupStatsFile(StringRef StatsFilename) {
+  // Setup output file to emit statistics.
+  if (StatsFilename.empty())
+    return nullptr;
+
+  llvm::EnableStatistics(false);
+  std::error_code EC;
+  auto StatsFile =
+      llvm::make_unique<ToolOutputFile>(StatsFilename, EC, sys::fs::F_None);
+  if (EC)
+    return errorCodeToError(EC);
+
+  StatsFile->keep();
+  return std::move(StatsFile);
+}
diff --git a/llvm/lib/LTO/LTOCodeGenerator.cpp b/llvm/lib/LTO/LTOCodeGenerator.cpp
index f02907f7a86..79d41ee8966 100644
--- a/llvm/lib/LTO/LTOCodeGenerator.cpp
+++ b/llvm/lib/LTO/LTOCodeGenerator.cpp
@@ -95,6 +95,11 @@ cl::opt<bool> LTOPassRemarksWithHotness(
     "lto-pass-remarks-with-hotness",
     cl::desc("With PGO, include profile count in optimization remarks"),
     cl::Hidden);
+
+cl::opt<std::string> LTOStatsFile(
+    "lto-stats-file",
+    cl::desc("Save statistics to the specified file"),
+    cl::Hidden);
 }
 
 LTOCodeGenerator::LTOCodeGenerator(LLVMContext &Context)
@@ -518,6 +523,14 @@ bool LTOCodeGenerator::optimize(bool DisableVerify, bool DisableInline,
   }
   DiagnosticOutputFile = std::move(*DiagFileOrErr);
 
+  // Setup output file to emit statistics.
+  auto StatsFileOrErr = lto::setupStatsFile(LTOStatsFile);
+  if (!StatsFileOrErr) {
+    errs() << "Error: " << toString(StatsFileOrErr.takeError()) << "\n";
+    report_fatal_error("Can't get an output file for the statistics");
+  }
+  StatsFile = std::move(StatsFileOrErr.get());
+
   // We always run the verifier once on the merged module, the `DisableVerify`
   // parameter only applies to subsequent verify.
   verifyMergedModuleOnce();
@@ -584,9 +597,13 @@ bool LTOCodeGenerator::compileOptimized(ArrayRef<raw_pwrite_stream *> Out) {
                               [&]() { return createTargetMachine(); }, FileType,
                               ShouldRestoreGlobalsLinkage);
 
-  // If statistics were requested, print them out after codegen.
-  if (llvm::AreStatisticsEnabled())
-    llvm::PrintStatistics();
+  // If statistics were requested, save them to the specified file or
+  // print them out after codegen.
+  if (StatsFile)
+    PrintStatisticsJSON(StatsFile->os());
+  else if (AreStatisticsEnabled())
+    PrintStatistics();
+
   reportAndResetTimings();
 
   finishOptimizationRemarks();