[flang][Driver] Preliminary support for -ftime-report (llvm#122894)

The behavior is not entirely consistent with that of clang for the
moment since detailed timing information on the LLVM IR optimization and
code generation passes is not provided. The -ftime-report= option is
also not enabled since that is only relevant for information about the
LLVM IR passes. However, some code to handle that option has been
included, to make it easier to support the option when the issues
blocking it are resolved. A FortranSupport library has been created that
is intended to mirror the LLVM and MLIR support libraries.

Based on @tarunprabhu's PR
llvm#107270 with minor changes
addressing latest review feedback. He's busy and we'd like to get this
support in ASAP.

Co-authored-by: Tarun Prabhu <[email protected]>

clang/include/clang/Driver/Options.td

@@ -4108,7 +4108,7 @@ defm ms_tls_guards : BoolFOption<"ms-tls-guards",
           "Do not emit code to perform on-demand initialization of thread-local variables">,
   PosFlag<SetTrue>>;
 def ftime_report : Flag<["-"], "ftime-report">, Group<f_Group>,
-  Visibility<[ClangOption, CC1Option]>,
+  Visibility<[ClangOption, CC1Option, FlangOption, FC1Option]>,
   MarshallingInfoFlag<CodeGenOpts<"TimePasses">>;
 def ftime_report_EQ: Joined<["-"], "ftime-report=">, Group<f_Group>,
   Visibility<[ClangOption, CC1Option]>, Values<"per-pass,per-pass-run">,

clang/lib/Driver/ToolChains/Flang.cpp

@@ -150,10 +150,12 @@ void Flang::addCodegenOptions(const ArgList &Args,
   if (shouldLoopVersion(Args))
     CmdArgs.push_back("-fversion-loops-for-stride");
 
-  Args.addAllArgs(CmdArgs, {options::OPT_flang_experimental_hlfir,
-                            options::OPT_flang_deprecated_no_hlfir,
-                            options::OPT_fno_ppc_native_vec_elem_order,
-                            options::OPT_fppc_native_vec_elem_order});
+  Args.addAllArgs(CmdArgs,
+                  {options::OPT_flang_experimental_hlfir,
+                   options::OPT_flang_deprecated_no_hlfir,
+                   options::OPT_fno_ppc_native_vec_elem_order,
+                   options::OPT_fppc_native_vec_elem_order,
+                   options::OPT_ftime_report, options::OPT_ftime_report_EQ});
 }
 
 void Flang::addPicOptions(const ArgList &Args, ArgStringList &CmdArgs) const {

flang/include/flang/Frontend/CompilerInstance.h

@@ -20,6 +20,7 @@
 #include "flang/Parser/provenance.h"
 #include "flang/Semantics/runtime-type-info.h"
 #include "flang/Semantics/semantics.h"
+#include "flang/Support/StringOstream.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetMachine.h"
 
@@ -85,6 +86,27 @@ class CompilerInstance {
   /// facilitate this. It is optional and will normally be just a nullptr.
   std::unique_ptr<llvm::raw_pwrite_stream> outputStream;
 
+  /// @name Timing
+  /// Objects needed when timing is enabled.
+  /// @{
+  /// The timing manager.
+  mlir::DefaultTimingManager timingMgr;
+
+  /// The root of the timingScope. This will be reset in @ref executeAction if
+  /// timers have been enabled.
+  mlir::TimingScope timingScopeRoot;
+
+  /// @name Timing stream
+  /// The output streams to capture the timing. Three different streams are
+  /// needed because the timing classes all work slightly differently. We create
+  /// these streams so we have control over when and how the timing is
+  /// displayed. Otherwise, the timing is only displayed when the corresponding
+  /// managers/timers go out of scope.
+  std::unique_ptr<Fortran::support::string_ostream> timingStreamMLIR;
+  std::unique_ptr<Fortran::support::string_ostream> timingStreamLLVM;
+  std::unique_ptr<Fortran::support::string_ostream> timingStreamCodeGen;
+  /// @}
+
 public:
   explicit CompilerInstance();
 
@@ -254,6 +276,42 @@ class CompilerInstance {
   /// Produces the string which represents target feature
   std::string getTargetFeatures();
 
+  /// {
+  /// @name Timing
+  /// @{
+  bool isTimingEnabled() const { return timingMgr.isEnabled(); }
+
+  mlir::DefaultTimingManager &getTimingManager() { return timingMgr; }
+  const mlir::DefaultTimingManager &getTimingManager() const {
+    return timingMgr;
+  }
+
+  mlir::TimingScope &getTimingScopeRoot() { return timingScopeRoot; }
+  const mlir::TimingScope &getTimingScopeRoot() const {
+    return timingScopeRoot;
+  }
+
+  /// Get the timing stream for the MLIR pass manager.
+  llvm::raw_ostream &getTimingStreamMLIR() {
+    assert(timingStreamMLIR && "Timing stream for MLIR was not set");
+    return *timingStreamMLIR;
+  }
+
+  /// Get the timing stream for the new LLVM pass manager.
+  llvm::raw_ostream &getTimingStreamLLVM() {
+    assert(timingStreamLLVM && "Timing stream for LLVM was not set");
+    return *timingStreamLLVM;
+  }
+
+  /// Get the timing stream fro the legacy LLVM pass manager.
+  /// NOTE: If the codegen is updated to use the new pass manager, this should
+  /// no longer be needed.
+  llvm::raw_ostream &getTimingStreamCodeGen() {
+    assert(timingStreamCodeGen && "Timing stream for codegen was not set");
+    return *timingStreamCodeGen;
+  }
+  /// @}
+
 private:
   /// Create a new output file
   ///

flang/include/flang/Frontend/CompilerInvocation.h

@@ -21,6 +21,7 @@
 #include "flang/Lower/LoweringOptions.h"
 #include "flang/Parser/parsing.h"
 #include "flang/Semantics/semantics.h"
+#include "mlir/Support/Timing.h"
 #include "clang/Basic/Diagnostic.h"
 #include "clang/Basic/DiagnosticOptions.h"
 #include "llvm/Option/ArgList.h"
@@ -143,6 +144,10 @@ class CompilerInvocation : public CompilerInvocationBase {
       },
   };
 
+  /// Whether to time the invocation. Set when -ftime-report or -ftime-report=
+  /// is enabled.
+  bool enableTimers;
+
 public:
   CompilerInvocation() = default;
 
@@ -222,6 +227,8 @@ class CompilerInvocation : public CompilerInvocationBase {
     return defaultKinds;
   }
 
+  bool getEnableTimers() const { return enableTimers; }
+
   /// Create a compiler invocation from a list of input options.
   /// \returns true on success.
   /// \returns false if an error was encountered while parsing the arguments

flang/include/flang/Support/StringOstream.h

@@ -0,0 +1,32 @@
+//===-- CompilerInstance.h - Flang Compiler Instance ------------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Coding style: https://mlir.llvm.org/getting_started/DeveloperGuide/
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef FORTRAN_SUPPORT_STRINGOSTREAM_H
+#define FORTRAN_SUPPORT_STRINGOSTREAM_H
+
+#include <llvm/Support/raw_ostream.h>
+
+namespace Fortran::support {
+
+/// Helper class to maintain both the an llvm::raw_string_ostream object and
+/// its associated buffer.
+class string_ostream : public llvm::raw_string_ostream {
+private:
+  std::string buf;
+
+public:
+  string_ostream() : llvm::raw_string_ostream(buf) {}
+};
+
+} // namespace Fortran::support
+
+#endif // FORTRAN_SUPPORT_STRINGOSTREAM_H

flang/include/flang/Support/Timing.h

@@ -0,0 +1,27 @@
+//===- Timing.h - Execution time measurement facilities ---------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Facilities to measure and provide statistics on execution time.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef FORTRAN_SUPPORT_TIMING_H
+#define FORTRAN_SUPPORT_TIMING_H
+
+#include "mlir/Support/Timing.h"
+
+namespace Fortran::support {
+
+/// Create a strategy to render the captured times in plain text. This is
+/// intended to be passed to a TimingManager.
+std::unique_ptr<mlir::OutputStrategy> createTimingFormatterText(
+    llvm::raw_ostream &os);
+
+} // namespace Fortran::support
+
+#endif // FORTRAN_SUPPORT_TIMING_H

flang/lib/CMakeLists.txt

@@ -4,6 +4,7 @@ add_subdirectory(Decimal)
 add_subdirectory(Lower)
 add_subdirectory(Parser)
 add_subdirectory(Semantics)
+add_subdirectory(Support)
 add_subdirectory(Frontend)
 add_subdirectory(FrontendTool)
 

flang/lib/Frontend/CMakeLists.txt

@@ -29,6 +29,7 @@ add_flang_library(flangFrontend
   FortranEvaluate
   FortranCommon
   FortranLower
+  FortranSupport
   FIRDialect
   FIRDialectSupport
   FIRSupport

flang/lib/Frontend/CompilerInstance.cpp

@@ -17,9 +17,12 @@
 #include "flang/Parser/parsing.h"
 #include "flang/Parser/provenance.h"
 #include "flang/Semantics/semantics.h"
+#include "flang/Support/Timing.h"
+#include "mlir/Support/RawOstreamExtras.h"
 #include "clang/Basic/DiagnosticFrontend.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/MC/TargetRegistry.h"
+#include "llvm/Pass.h"
 #include "llvm/Support/Errc.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/FileSystem.h"
@@ -147,7 +150,7 @@ void CompilerInstance::clearOutputFiles(bool eraseFiles) {
 }
 
 bool CompilerInstance::executeAction(FrontendAction &act) {
-  auto &invoc = this->getInvocation();
+  CompilerInvocation &invoc = this->getInvocation();
 
   llvm::Triple targetTriple{llvm::Triple(invoc.getTargetOpts().triple)};
   if (targetTriple.getArch() == llvm::Triple::ArchType::x86_64) {
@@ -167,6 +170,25 @@ bool CompilerInstance::executeAction(FrontendAction &act) {
   // Set options controlling lowering to FIR.
   invoc.setLoweringOptions();
 
+  if (invoc.getEnableTimers()) {
+    llvm::TimePassesIsEnabled = true;
+
+    timingStreamMLIR = std::make_unique<Fortran::support::string_ostream>();
+    timingStreamLLVM = std::make_unique<Fortran::support::string_ostream>();
+    timingStreamCodeGen = std::make_unique<Fortran::support::string_ostream>();
+
+    timingMgr.setEnabled(true);
+    timingMgr.setDisplayMode(mlir::DefaultTimingManager::DisplayMode::Tree);
+    timingMgr.setOutput(
+        Fortran::support::createTimingFormatterText(*timingStreamMLIR));
+
+    // Creating a new TimingScope will automatically start the timer. Since this
+    // is the top-level timer, this is ok because it will end up capturing the
+    // time for all the bookkeeping and other tasks that take place between
+    // parsing, lowering etc. for which finer-grained timers will be created.
+    timingScopeRoot = timingMgr.getRootScope();
+  }
+
   // Run the frontend action `act` for every input file.
   for (const FrontendInputFile &fif : getFrontendOpts().inputs) {
     if (act.beginSourceFile(*this, fif)) {
@@ -176,6 +198,34 @@ bool CompilerInstance::executeAction(FrontendAction &act) {
       act.endSourceFile();
     }
   }
+
+  if (timingMgr.isEnabled()) {
+    timingScopeRoot.stop();
+
+    // Write the timings to the associated output stream and clear all timers.
+    // We need to provide another stream because the TimingManager will attempt
+    // to print in its destructor even if it has been cleared. By the time that
+    // destructor runs, the output streams will have been destroyed, so give it
+    // a null stream.
+    timingMgr.print();
+    timingMgr.setOutput(
+        Fortran::support::createTimingFormatterText(mlir::thread_safe_nulls()));
+
+    // This prints the timings in "reverse" order, starting from code
+    // generation, followed by LLVM-IR optimizations, then MLIR optimizations
+    // and transformations and the frontend. If any of the steps are disabled,
+    // for instance because code generation was not performed, the strings
+    // will be empty.
+    if (!timingStreamCodeGen->str().empty())
+      llvm::errs() << timingStreamCodeGen->str() << "\n";
+
+    if (!timingStreamLLVM->str().empty())
+      llvm::errs() << timingStreamLLVM->str() << "\n";
+
+    if (!timingStreamMLIR->str().empty())
+      llvm::errs() << timingStreamMLIR->str() << "\n";
+  }
+
   return !getDiagnostics().getClient()->getNumErrors();
 }
 

flang/lib/Frontend/CompilerInvocation.cpp

@@ -1436,6 +1436,10 @@ bool CompilerInvocation::createFromArgs(
     }
   }
 
+  // Process the timing-related options.
+  if (args.hasArg(clang::driver::options::OPT_ftime_report))
+    invoc.enableTimers = true;
+
   invoc.setArgv0(argv0);
 
   return success;