[Clang][CMake] Support perf, LBR, and Instrument CLANG_BOLT options

[Amir]

Summary

Split up and refactor CLANG_BOLT_INSTRUMENT into support for
perf no-LBR and perf with LBR profiling modes.

[Amir]

Add perf and perf+LBR support

[Amir]

Reduce changes

[Amir]

Reduce changes

[Amir]

Reduce changes

[Amir]

Reduce changes

[Amir]

Reduce changes

[Amir]

Rebase

[Amir]

Rebase

[Amir]

Ping @beanz, @phosek

[Amir]

Rebase + reformatted with black (D150761)

[phosek]

clang/utils/perf-training/bolt.lit.cfg

12

This name would ideally be passed through the generated lit.site.cfg rather than hardcoding it here.

clang/utils/perf-training/perf-helper.py

64

This could be omitted.

74

Can we remove this?

77–86

Why not assign to perf_args directly?

104

I'd call it llvm-bolt for simplicity.

107–109

I'd consider providing both --lbr and --no-lbr options.

112–115

Why not assign to p2b_args directly?

[Amir]

Address comments

[Amir]

clang/utils/perf-training/perf-helper.py

64

I think it's best to keep it as optional argument, not positional.

[Amir]

Fix instrumentation mode

[Amir]

Set CLANG_BOLT_INSTRUMENTED in parent scope too.

[Amir]

Make the name of BOLT-instrumented Clang binary (CLANG_BOLT_INSTRUMENTED)
a user-settable cache variable

[Amir]

Migrated to https://github.com/llvm/llvm-project/pull/69133

clang/CMakeLists.txt

foreach(target ${CLANG_BOOTSTRAP_TARGETS})
     if(target MATCHES "^stage[0-9]*")
       add_custom_target(${target} DEPENDS ${NEXT_CLANG_STAGE}-${target})
     endif()
 
     ExternalProject_Add_StepTargets(${NEXT_CLANG_STAGE} ${target})
   endforeach()
 endif()
 
-if (CLANG_BOLT_INSTRUMENT AND NOT LLVM_BUILD_INSTRUMENTED)
+set(CLANG_BOLT "INSTRUMENT" CACHE STRING "Apply BOLT optimization to Clang. \
+  May be specified as Instrument or Perf or LBR to use a particular profiling \
+  mechanism.")
+string(TOUPPER "${CLANG_BOLT}" uppercase_CLANG_BOLT)
+
+if (CLANG_BOLT AND NOT LLVM_BUILD_INSTRUMENTED)
   set(CLANG_PATH ${LLVM_RUNTIME_OUTPUT_INTDIR}/clang)
   set(CLANG_INSTRUMENTED ${CLANG_PATH}-bolt.inst)
 
+  # Pass extra flag in no-LBR mode
+  if (uppercase_CLANG_BOLT STREQUAL "PERF")
+    set(BOLT_NO_LBR "-nl")
+  endif()
+
+  if (uppercase_CLANG_BOLT STREQUAL "INSTRUMENT")
     # Instrument clang with BOLT
     add_custom_target(clang-instrumented
       DEPENDS ${CLANG_INSTRUMENTED}
     )
     set(BOLT_FDATA ${CMAKE_CURRENT_BINARY_DIR}/utils/perf-training/prof.fdata)
     add_custom_command(OUTPUT ${CLANG_INSTRUMENTED}
       DEPENDS clang llvm-bolt
       COMMAND llvm-bolt ${CLANG_PATH} -o ${CLANG_INSTRUMENTED}
         -instrument --instrumentation-file-append-pid
         --instrumentation-file=${BOLT_FDATA}
       COMMENT "Instrumenting clang binary with BOLT"
       VERBATIM
     )
+    add_custom_target(clang-bolt-training-deps DEPENDS clang-instrumented)
+  else() # perf or LBR
+    add_custom_target(clang-bolt-training-deps DEPENDS clang)
+  endif()
 
   # Optimize original (pre-bolt) Clang using the collected profile
   set(CLANG_OPTIMIZED ${CMAKE_CURRENT_BINARY_DIR}/clang.bolt)
   add_custom_target(clang-bolt
     DEPENDS merge-bolt-fdata
     COMMAND llvm-bolt ${CLANG_PATH}
       -o ${CLANG_OPTIMIZED}
       -data ${BOLT_FDATA}
       -reorder-blocks=ext-tsp -reorder-functions=hfsort+ -split-functions
       -split-all-cold -split-eh -dyno-stats -icf=1 -use-gnu-stack
+      ${BOLT_NO_LBR}
     COMMAND ${CMAKE_COMMAND} -E rename ${CLANG_OPTIMIZED} $<TARGET_FILE:clang>
     COMMENT "Optimizing Clang with BOLT"
     VERBATIM
   )
 endif()
 
 if (LLVM_ADD_NATIVE_VISUALIZERS_TO_SOLUTION)
   add_subdirectory(utils/ClangVisualizers)

clang/cmake/caches/BOLT.cmake

 set(CMAKE_BUILD_TYPE Release CACHE STRING "")
-set(CLANG_BOLT_INSTRUMENT ON CACHE BOOL "")
+set(CLANG_BOLT "INSTRUMENT" CACHE STRING "")
 set(CMAKE_EXE_LINKER_FLAGS "-Wl,--emit-relocs,-znow" CACHE STRING "")
 
 set(LLVM_ENABLE_PROJECTS "bolt;clang" CACHE STRING "")
 set(LLVM_TARGETS_TO_BUILD Native CACHE STRING "")
 
 # Disable function splitting enabled by default in GCC8+
 if("${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU")
   set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fno-reorder-blocks-and-partition")
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-reorder-blocks-and-partition")
 endif()

clang/utils/perf-training/CMakeLists.txt

if(APPLE AND DTRACE)
   endif()
 
   add_custom_target(generate-order-file
     COMMAND "${Python3_EXECUTABLE}" ${CMAKE_CURRENT_SOURCE_DIR}/perf-helper.py gen-order-file --binary $<TARGET_FILE:clang> --output ${CLANG_ORDER_FILE} ${CMAKE_CURRENT_BINARY_DIR}
     COMMENT "Generating order file"
     DEPENDS generate-dtrace-logs)
 endif()
 
-if(CLANG_BOLT_INSTRUMENT AND NOT LLVM_BUILD_INSTRUMENTED)
+if(CLANG_BOLT AND NOT LLVM_BUILD_INSTRUMENTED)
   configure_lit_site_cfg(
     ${CMAKE_CURRENT_SOURCE_DIR}/bolt.lit.site.cfg.in
     ${CMAKE_CURRENT_BINARY_DIR}/bolt-fdata/lit.site.cfg
     )
 
   add_lit_testsuite(generate-bolt-fdata "Generating BOLT profile for Clang"
     ${CMAKE_CURRENT_BINARY_DIR}/bolt-fdata/
     EXCLUDE_FROM_CHECK_ALL
-    DEPENDS clang-instrumented clear-bolt-fdata
+    DEPENDS clang-bolt-training-deps clear-bolt-fdata clear-perf-data
     )
 
   add_custom_target(clear-bolt-fdata
     COMMAND "${Python3_EXECUTABLE}" ${CMAKE_CURRENT_SOURCE_DIR}/perf-helper.py clean ${CMAKE_CURRENT_BINARY_DIR} fdata
     COMMENT "Clearing old BOLT fdata")
 
+  add_custom_target(clear-perf-data
+    COMMAND "${Python3_EXECUTABLE}" ${CMAKE_CURRENT_SOURCE_DIR}/perf-helper.py clean ${CMAKE_CURRENT_BINARY_DIR} perf.data
+    COMMENT "Clearing old perf data")
+
+  string(TOUPPER "${CLANG_BOLT}" uppercase_CLANG_BOLT)
+  # Pass extra flag in no-LBR mode
+  if (uppercase_CLANG_BOLT STREQUAL "PERF")
+    set(BOLT_NO_LBR "--nolbr")
+  endif()
+
+  add_custom_target(merge-fdata-deps)
+  if (uppercase_CLANG_BOLT STREQUAL "INSTRUMENT")
+    add_dependencies(merge-fdata-deps generate-bolt-fdata)
+  else()
+    # Convert perf profiles into fdata
+    add_custom_target(convert-perf-fdata
+      COMMAND "${Python3_EXECUTABLE}" ${CMAKE_CURRENT_SOURCE_DIR}/perf-helper.py perf2bolt $<TARGET_FILE:llvm-bolt> ${CMAKE_CURRENT_BINARY_DIR} $<TARGET_FILE:clang> ${BOLT_NO_LBR}
+      COMMENT "Converting perf files to BOLT fdata"
+      DEPENDS llvm-bolt generate-bolt-fdata)
+    add_dependencies(merge-fdata-deps convert-perf-fdata)
+  endif()
+
   # Merge profiles into one using merge-fdata
   add_custom_target(merge-bolt-fdata
     COMMAND "${Python3_EXECUTABLE}" ${CMAKE_CURRENT_SOURCE_DIR}/perf-helper.py merge-fdata $<TARGET_FILE:merge-fdata> ${CMAKE_CURRENT_BINARY_DIR}/prof.fdata ${CMAKE_CURRENT_BINARY_DIR}
     COMMENT "Merging BOLT fdata"
-    DEPENDS merge-fdata generate-bolt-fdata)
+    DEPENDS merge-fdata merge-fdata-deps)
 endif()

clang/utils/perf-training/bolt.lit.cfg

 # -*- Python -*-
 
 from lit import Test
 import lit.formats
 import lit.util
 import os
 import subprocess
 
-config.clang = os.path.realpath(lit.util.which('clang-bolt.inst', config.clang_tools_dir)).replace('\\', '/')
+clang_binary = 'clang'
+perf_wrapper = ''
+if config.clang_bolt_mode.lower() == "instrument":
+  clang_binary = 'clang-bolt.inst'
+else: # perf or LBR
+  perf_wrapper = '%s %s/perf-helper.py perf' % (config.python_exe, config.perf_helper_dir)
+  if config.clang_bolt_mode.lower() == "lbr":
+    perf_wrapper += " --lbr"
+  perf_wrapper += " -- "
+
+config.clang = os.path.realpath(lit.util.which(clang_binary, config.clang_tools_dir)).replace('\\', '/')
 
 config.name = 'Clang Perf Training'
 config.suffixes = ['.c', '.cc', '.cpp', '.m', '.mm', '.cu', '.ll', '.cl', '.s', '.S', '.modulemap', '.test']
 
 use_lit_shell = os.environ.get("LIT_USE_INTERNAL_SHELL")
 config.test_format = lit.formats.ShTest(use_lit_shell == "0")
-config.substitutions.append( ('%clang_cpp_skip_driver', ' %s --driver-mode=g++ ' % (config.clang)))
-config.substitutions.append( ('%clang_cpp', ' %s --driver-mode=g++ ' % (config.clang)))
-config.substitutions.append( ('%clang_skip_driver', ' %s ' % (config.clang)))
-config.substitutions.append( ('%clang', ' %s ' % (config.clang) ) )
+config.substitutions.append( ('%clang_cpp_skip_driver', ' %s %s --driver-mode=g++ ' % (perf_wrapper, config.clang)))
+config.substitutions.append( ('%clang_cpp', ' %s %s --driver-mode=g++ ' % (perf_wrapper, config.clang)))
+config.substitutions.append( ('%clang_skip_driver', ' %s %s ' % (perf_wrapper, config.clang)))
+config.substitutions.append( ('%clang', ' %s %s ' % (perf_wrapper, config.clang) ) )
 config.substitutions.append( ('%test_root', config.test_exec_root ) )

clang/utils/perf-training/bolt.lit.site.cfg.in

 @LIT_SITE_CFG_IN_HEADER@
 
 import sys
 
 config.clang_tools_dir = lit_config.substitute("@CURRENT_TOOLS_DIR@")
 config.perf_helper_dir = "@CMAKE_CURRENT_SOURCE_DIR@"
 config.test_exec_root = "@CMAKE_CURRENT_BINARY_DIR@"
 config.test_source_root = "@CLANG_PGO_TRAINING_DATA@"
 config.target_triple = "@LLVM_TARGET_TRIPLE@"
 config.python_exe = "@Python3_EXECUTABLE@"
 config.clang_obj_root = path(r"@CLANG_BINARY_DIR@")
+config.clang_bolt_mode = "@CLANG_BOLT@"
 
 # Let the main config do the real work.
 lit_config.load_config(config, "@CLANG_SOURCE_DIR@/utils/perf-training/bolt.lit.cfg")

clang/utils/perf-training/perf-helper.py

if len(args) != 3:
     print('Usage: %s merge-fdata <merge-fdata> <output> <path>\n' % __file__ +
       '\tMerges all fdata files from path into output.')
     return 1
   cmd = [args[0], '-o', args[1]]
   cmd.extend(findFilesWithExtension(args[2], "fdata"))
   subprocess.check_call(cmd)
   return 0
 
+def perf(args):
+  parser = argparse.ArgumentParser(prog='perf-helper perf',
+    description='perf wrapper for BOLT profile collection')
+  parser.add_argument('--lbr', required=False, action='store_true',
+    help='Use perf with branch stacks')
+  parser.add_argument('cmd', nargs='*', help='')
+
+  # Use python's arg parser to handle all leading option arguments, but pass
+  # everything else through to perf
+  first_cmd = next(arg for arg in args if not arg.startswith("--"))
+  last_arg_idx = args.index(first_cmd)
+
+  opts = parser.parse_args(args[:last_arg_idx])
+  #cmd = shlex.split(args[last_arg_idx:])
+  cmd = args[last_arg_idx:]
+
+  perf_args = []
+  perf_args.extend((
+    'perf', 'record', '--event=cycles:u', '--freq=max',
+    '--output=%d.perf.data' % os.getpid()))
+  if opts.lbr:
+    perf_args += ['--branch-filter=any,u']
+  perf_args.extend(cmd)
+
+  start_time = time.time()
+  subprocess.check_call(perf_args)
+
+  elapsed = time.time() - start_time
+  print("... data collection took %.4fs" % elapsed)
+  return 0
+
+def perf2bolt(args):
+  parser = argparse.ArgumentParser(prog='perf-helper perf2bolt',
+    description='perf2bolt conversion wrapper for perf.data files')
+  parser.add_argument('p2b_path', help='Path to llvm-bolt')
+  parser.add_argument('path', help='Path containing perf.data files')
+  parser.add_argument('binary', help='Input binary')
+  parser.add_argument('--nolbr', required=False, action='store_true',
+    help='Use -nl perf2bolt mode')
+  opts = parser.parse_args(args)
+
+  p2b_args = []
+  p2b_args.extend((opts.p2b_path, opts.binary, '--aggregate-only',
+    '--profile-format=yaml'))
+  if opts.nolbr:
+    p2b_args += ['-nl']
+  p2b_args += ['-p']
+  for filename in findFilesWithExtension(opts.path, 'perf.data'):
+    subprocess.check_call(p2b_args + [filename, '-o', filename+'.fdata'])
+  return 0
+
 def dtrace(args):
   parser = argparse.ArgumentParser(prog='perf-helper dtrace',
     description='dtrace wrapper for order file generation')
   parser.add_argument('--buffer-size', metavar='size', type=int, required=False,
     default=1, help='dtrace buffer size in MB (default 1)')
   parser.add_argument('--use-oneshot', required=False, action='store_true',
     help='Use dtrace\'s oneshot probes')
   parser.add_argument('--use-ustack', required=False, action='store_true',
     help='Use dtrace\'s ustack to print function names')
   parser.add_argument('--cc1', required=False, action='store_true',
     help='Execute cc1 directly (don\'t profile the driver)')
   parser.add_argument('cmd', nargs='*', help='')
 
   # Use python's arg parser to handle all leading option arguments, but pass
def genOrderFile(args):
   return 0
 
 commands = {'clean' : clean,
   'merge' : merge,
   'dtrace' : dtrace,
   'cc1' : cc1,
   'gen-order-file' : genOrderFile,
   'merge-fdata' : merge_fdata,
+  'perf' : perf,
+  'perf2bolt' : perf2bolt,
   }
 
 def main():
   f = commands[sys.argv[1]]
   sys.exit(f(sys.argv[2:]))
 
 if __name__ == '__main__':
   main()