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[Clang][CMake] Add CSSPGO support to LLVM_BUILD_INSTRUMENTED (#79942)

Browse Source 
Build on Clang-BOLT infrastructure to collect sample profile for CSSPGO.
Add CSSPGO.cmake and BOLT-CSSPGO.cmake to automate CSSPGO/+BOLT 
Clang builds.

Note that `CLANG_PGO_TRAINING_DATA_SOURCE_DIR` is required as built-in 
training set is inadequate for collecting sampled profile.

Hardware compatibility: CSSPGO requires synchronized (0-skid) call
and branch stacks, which is only available with Intel PEBS (Sandy
Bridge+),
AMD Zen3 with BRS, Zen4 with LBRv2+LBR_PMC_FREEZE, and Zen5 with LBRv2.
This patch adds support for Intel `br_inst_retired.near_taken:uppp`
event.

Test Plan:
Added BOLT-CSSPGO.cmake with same use as BOLT-PGO.cmake, 
e.g. for bootstrapped ThinLTO+CSSPGO+BOLT, with CSSPGO profile collected
from LLVM build, and BOLT profile collected from Hello World
(instrumentation):
```
cmake -B clang-csspgo-bolt -S /path/to/llvm-project/llvm \
-DLLVM_ENABLE_LLD=ON -DBOOTSTRAP_LLVM_ENABLE_LLD=ON \
-DBOOTSTRAP_BOOTSTRAP_LLVM_ENABLE_LLD=ON \
-DPGO_INSTRUMENT_LTO=Thin \
-DBOOTSTRAP_CLANG_PGO_TRAINING_DATA_SOURCE_DIR=/path/to/llvm-project/llvm \
-GNinja  -C /path/to/llvm-project/clang/cmake/caches/BOLT-CSSPGO.cmake
ninja stage2-clang-bolt
...
warning: Sample PGO is estimated to optimize better with 19.5x more samples. Please consider increasing sampling rate or profiling for longer duration to get more samples.
...
[2800/2801] Optimizing Clang with BOLT
BOLT-INFO: 8189 out of 106942 functions in the binary (7.7%) have non-empty execution profile
            13776393 : taken branches (-42.1%)
```

Performance testing with Clang:
- Setup: Clang-BOLT testing harness
9f2b46f67a
  - CSSPGO training: building LLVM, 
  - InstrPGO training: building Hello World,
  - BOLT training: building Hello World, instrumentation,
  - benchmark: building small LLVM tool (not),
- 2S Intel SKX Xeon 6138 with 40C/80T and 256GB RAM, using 20C/40T for
build,
- Results, wall time, lower is better
  - Baseline (bootstrapped build): 10.36s,
  - InstrPGO + ThinLTO: 9.34s,
  - CSSPGO + ThinLTO: 8.85s.
- BOLT results, for reference:
  - Baseline: 9.09s,
  - InstrPGO + ThinLTO: 9.09s,
  - CSSPGO + ThinLTO: 8.58s.

---------

Co-authored-by: Matthias Braun <matze@braunis.de>
This commit is contained in:
Amir Ayupov 2025-10-01 15:25:34 -07:00 committed by GitHub
parent 1e4d4bb584
commit 780f69cd92
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
8 changed files with 136 additions and 21 deletions
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15
clang/CMakeLists.txt
View File

@ -754,11 +754,22 @@ if (CLANG_ENABLE_BOOTSTRAP)
if(BOOTSTRAP_LLVM_BUILD_INSTRUMENTED)
add_dependencies(clang-bootstrap-deps llvm-profdata)
set(PGO_OPT -DLLVM_PROFDATA=${LLVM_RUNTIME_OUTPUT_INTDIR}/llvm-profdata)
string(TOUPPER "${BOOTSTRAP_LLVM_BUILD_INSTRUMENTED}" BOOTSTRAP_LLVM_BUILD_INSTRUMENTED)
if (BOOTSTRAP_LLVM_BUILD_INSTRUMENTED STREQUAL "CSSPGO")
add_dependencies(clang-bootstrap-deps llvm-profgen)
list(APPEND PGO_OPT -DLLVM_PROFGEN=${LLVM_RUNTIME_OUTPUT_INTDIR}/llvm-profgen)
endif()
endif()
if(LLVM_BUILD_INSTRUMENTED)
add_dependencies(clang-bootstrap-deps generate-profdata)
set(PGO_OPT -DLLVM_PROFDATA_FILE=${CMAKE_CURRENT_BINARY_DIR}/utils/perf-training/clang.profdata)
string(TOUPPER "${LLVM_BUILD_INSTRUMENTED}" LLVM_BUILD_INSTRUMENTED)
if (LLVM_BUILD_INSTRUMENTED STREQUAL "CSSPGO")
add_dependencies(clang-bootstrap-deps generate-sprofdata)
set(PGO_OPT -DLLVM_SPROFDATA_FILE=${CMAKE_CURRENT_BINARY_DIR}/utils/perf-training/clang.sprofdata)
else()
add_dependencies(clang-bootstrap-deps generate-profdata)
set(PGO_OPT -DLLVM_PROFDATA_FILE=${CMAKE_CURRENT_BINARY_DIR}/utils/perf-training/clang.profdata)
endif()
# Use the current tools for LTO instead of the instrumented ones
list(APPEND _BOOTSTRAP_DEFAULT_PASSTHROUGH
CMAKE_CXX_COMPILER

3
clang/cmake/caches/BOLT-CSSPGO.cmake Normal file
View File

@ -0,0 +1,3 @@
set(BOLT_PGO_CMAKE_CACHE "CSSPGO" CACHE STRING "")
set(BOOTSTRAP_CMAKE_BUILD_TYPE RelWithDebInfo CACHE STRING "")
include(${CMAKE_CURRENT_LIST_DIR}/BOLT-PGO.cmake)

3
clang/cmake/caches/BOLT-PGO.cmake
View File

@ -1,3 +1,4 @@
set(BOLT_PGO_CMAKE_CACHE "PGO" CACHE STRING "")
set(LLVM_ENABLE_PROJECTS "bolt;clang;lld" CACHE STRING "")
set(CLANG_BOOTSTRAP_TARGETS
@ -14,4 +15,4 @@ set(BOOTSTRAP_CLANG_BOOTSTRAP_TARGETS
set(PGO_BUILD_CONFIGURATION
${CMAKE_CURRENT_LIST_DIR}/BOLT.cmake
CACHE STRING "")
include(${CMAKE_CURRENT_LIST_DIR}/PGO.cmake)
include(${CMAKE_CURRENT_LIST_DIR}/${BOLT_PGO_CMAKE_CACHE}.cmake)

2
clang/cmake/caches/CSSPGO.cmake Normal file
View File

@ -0,0 +1,2 @@
set(BOOTSTRAP_LLVM_BUILD_INSTRUMENTED "CSSPGO" CACHE STRING "")
include(${CMAKE_CURRENT_LIST_DIR}/PGO.cmake)

36
clang/utils/perf-training/CMakeLists.txt
View File

@ -6,6 +6,10 @@ set(CLANG_PGO_TRAINING_DATA "${CMAKE_CURRENT_SOURCE_DIR}" CACHE PATH
set(CLANG_PGO_TRAINING_DATA_SOURCE_DIR OFF CACHE STRING "Path to source directory containing cmake project with source files to use for generating pgo data")
set(CLANG_PGO_TRAINING_DEPS "" CACHE STRING "Extra dependencies needed to build the PGO training data.")
add_custom_target(clear-perf-data
COMMAND "${Python3_EXECUTABLE}" ${CMAKE_CURRENT_SOURCE_DIR}/perf-helper.py clean ${CMAKE_CURRENT_BINARY_DIR} perf.data
COMMENT "Clearing old perf data")
option(CLANG_PGO_TRAINING_USE_LLVM_BUILD "Use LLVM build for generating PGO data" ON)
llvm_canonicalize_cmake_booleans(
@ -21,7 +25,7 @@ if(LLVM_BUILD_INSTRUMENTED)
add_lit_testsuite(generate-profraw "Generating clang PGO data"
${CMAKE_CURRENT_BINARY_DIR}/pgo-data/
EXCLUDE_FROM_CHECK_ALL
DEPENDS clear-profraw
DEPENDS clear-profraw clang
)
add_custom_target(clear-profraw
@ -55,6 +59,32 @@ if(LLVM_BUILD_INSTRUMENTED)
USE_TOOLCHAIN EXLUDE_FROM_ALL NO_INSTALL DEPENDS generate-profraw)
add_dependencies(generate-profdata generate-profraw-external)
endif()
if(NOT LLVM_PROFGEN)
find_program(LLVM_PROFGEN llvm-profgen)
endif()
if(NOT LLVM_PROFGEN)
message(STATUS "To enable converting CSSPGO samples LLVM_PROFGEN has to point to llvm-profgen")
elseif(NOT CLANG_PGO_TRAINING_DATA_SOURCE_DIR)
message(STATUS "CLANG_PGO_TRAINING_DATA_SOURCE_DIR must be set to collect CSSPGO samples")
else()
set(PERF_HELPER "${Python3_EXECUTABLE}" ${CMAKE_CURRENT_SOURCE_DIR}/perf-helper.py)
set(CLANG_SPROFDATA ${CMAKE_CURRENT_BINARY_DIR}/clang.sprofdata)
add_custom_command(
OUTPUT ${CLANG_SPROFDATA}
# Execute generate-profraw-external under perf
COMMAND ${PERF_HELPER} perf --csspgo -- ${CMAKE_COMMAND} --build ${CMAKE_BINARY_DIR} --target generate-profraw-external
# Convert perf profile into profraw
COMMAND ${PERF_HELPER} perf2prof ${LLVM_PROFGEN} $<TARGET_FILE:clang> ${CMAKE_CURRENT_BINARY_DIR}
# Merge profdata
COMMAND ${PERF_HELPER} merge --sample ${LLVM_PROFDATA} ${CLANG_SPROFDATA} ${CMAKE_CURRENT_BINARY_DIR}
DEPENDS clang ${CLANG_PGO_TRAINING_DEPS} clear-perf-data generate-profraw-external-clean
VERBATIM
USES_TERMINAL
)
add_custom_target(generate-sprofdata DEPENDS ${CLANG_SPROFDATA})
endif()
endif()
endif()
@ -104,8 +134,4 @@ if(CLANG_BOLT AND NOT LLVM_BUILD_INSTRUMENTED)
COMMAND "${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")
endif()

65
clang/utils/perf-training/perf-helper.py
View File

@ -45,14 +45,22 @@ def clean(args):
def merge(args):
if len(args) < 3:
print(
"Usage: %s merge <llvm-profdata> <output> <paths>\n" % __file__
+ "\tMerges all profraw files from path into output."
)
return 1
cmd = [args[0], "merge", "-o", args[1]]
for path in args[2:]:
parser = argparse.ArgumentParser(
prog="perf-helper merge",
description="Merges all profraw files from path(s) into output",
)
parser.add_argument("profdata", help="Path to llvm-profdata tool")
parser.add_argument("output", help="Output filename")
parser.add_argument(
"paths", nargs="+", help="Folder(s) containing input profraw files"
)
parser.add_argument("--sample", action="store_true", help="Sample profile")
opts = parser.parse_args(args)
cmd = [opts.profdata, "merge", "-o", opts.output]
if opts.sample:
cmd += ["--sample"]
for path in opts.paths:
cmd.extend(findFilesWithExtension(path, "profraw"))
subprocess.check_call(cmd)
return 0
@ -73,25 +81,30 @@ def merge_fdata(args):
def perf(args):
parser = argparse.ArgumentParser(
prog="perf-helper perf", description="perf wrapper for BOLT profile collection"
prog="perf-helper perf",
description="perf wrapper for BOLT/CSSPGO profile collection",
)
parser.add_argument(
"--lbr", action="store_true", help="Use perf with branch stacks"
)
parser.add_argument("--csspgo", action="store_true", help="Enable CSSPGO flags")
parser.add_argument("cmd", nargs=argparse.REMAINDER, help="")
opts = parser.parse_args(args)
cmd = opts.cmd[1:]
event = "br_inst_retired.near_taken:uppp" if opts.csspgo else "cycles:u"
perf_args = [
"perf",
"record",
"--event=cycles:u",
f"--event={event}",
"--freq=max",
"--output=%d.perf.data" % os.getpid(),
]
if opts.lbr:
if opts.lbr or opts.csspgo:
perf_args += ["--branch-filter=any,u"]
if opts.csspgo:
perf_args += ["-g", "--call-graph=fp"]
perf_args.extend(cmd)
start_time = time.time()
@ -127,6 +140,30 @@ def perf2bolt(args):
return 0
def perf2prof(args):
parser = argparse.ArgumentParser(
prog="perf-helper perf2prof",
description="perf to CSSPGO prof conversion wrapper",
)
parser.add_argument("profgen", help="Path to llvm-profgen binary")
parser.add_argument("binary", help="Input binary")
parser.add_argument("paths", nargs="+", help="Path containing perf.data files")
opts = parser.parse_args(args)
profgen_args = [opts.profgen, f"--binary={opts.binary}"]
for path in opts.paths:
for filename in findFilesWithExtension(path, "perf.data"):
subprocess.run(
[
*profgen_args,
f"--perfdata={filename}",
f"--output={filename}.profraw",
],
check=True,
)
return 0
def dtrace(args):
parser = argparse.ArgumentParser(
prog="perf-helper dtrace",
@ -660,7 +697,10 @@ def bolt_optimize(args):
process.check_returncode()
if opts.method in ["PERF", "LBR"]:
perf2bolt([opts.bolt, opts.perf_training_binary_dir, opts.input])
args = [opts.bolt, opts.perf_training_binary_dir, opts.input]
if opts.method == "LBR":
args.extend("--lbr")
perf2bolt(args)
merge_fdata([opts.merge_fdata, opts.fdata, opts.perf_training_binary_dir])
@ -707,6 +747,7 @@ commands = {
"merge-fdata": merge_fdata,
"perf": perf,
"perf2bolt": perf2bolt,
"perf2prof": perf2prof,
}

3
llvm/CMakeLists.txt
View File

@ -1011,6 +1011,9 @@ set(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR ${LLVM_ENABLE_PER_TARGET_RUNTIME_DIR_defa
set(LLVM_PROFDATA_FILE "" CACHE FILEPATH
"Profiling data file to use when compiling in order to improve runtime performance.")
set(LLVM_SPROFDATA_FILE "" CACHE FILEPATH
"Sampling profiling data file to use when compiling in order to improve runtime performance.")
if(LLVM_INCLUDE_TESTS)
# All LLVM Python files should be compatible down to this minimum version.
set(LLVM_MINIMUM_PYTHON_VERSION 3.8)

30
llvm/cmake/modules/HandleLLVMOptions.cmake
View File

@ -1184,7 +1184,7 @@ if(LLVM_ENABLE_EH AND NOT LLVM_ENABLE_RTTI)
message(FATAL_ERROR "Exception handling requires RTTI. You must set LLVM_ENABLE_RTTI to ON")
endif()
set(LLVM_BUILD_INSTRUMENTED OFF CACHE STRING "Build LLVM and tools with PGO instrumentation. May be specified as IR or Frontend")
set(LLVM_BUILD_INSTRUMENTED OFF CACHE STRING "Build LLVM and tools with PGO instrumentation. May be specified as IR, Frontend, CSIR, CSSPGO")
set(LLVM_VP_COUNTERS_PER_SITE "1.5" CACHE STRING "Value profile counters to use per site for IR PGO with Clang")
mark_as_advanced(LLVM_BUILD_INSTRUMENTED LLVM_VP_COUNTERS_PER_SITE)
string(TOUPPER "${LLVM_BUILD_INSTRUMENTED}" uppercase_LLVM_BUILD_INSTRUMENTED)
@ -1217,6 +1217,19 @@ if (LLVM_BUILD_INSTRUMENTED)
CMAKE_EXE_LINKER_FLAGS
CMAKE_SHARED_LINKER_FLAGS)
endif()
elseif(uppercase_LLVM_BUILD_INSTRUMENTED STREQUAL "CSSPGO")
if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
append("-fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -fno-optimize-sibling-calls -fpseudo-probe-for-profiling -fdebug-info-for-profiling"
CMAKE_CXX_FLAGS
CMAKE_C_FLAGS)
if(NOT LINKER_IS_LLD_LINK)
append("-fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -fno-optimize-sibling-calls -fpseudo-probe-for-profiling -fdebug-info-for-profiling"
CMAKE_EXE_LINKER_FLAGS
CMAKE_SHARED_LINKER_FLAGS)
endif()
else()
message(FATAL_ERROR "LLVM_BUILD_INSTRUMENTED=CSSPGO can only be specified when compiling with clang")
endif()
else()
append("-fprofile-instr-generate=\"${LLVM_PROFILE_FILE_PATTERN}\""
CMAKE_CXX_FLAGS
@ -1269,6 +1282,21 @@ elseif(LLVM_PROFDATA_FILE)
message(WARNING "LLVM_PROFDATA_FILE specified, but ${LLVM_PROFDATA_FILE} not found")
endif()
if(LLVM_SPROFDATA_FILE AND EXISTS ${LLVM_SPROFDATA_FILE})
if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang" )
append("-fpseudo-probe-for-profiling -fprofile-sample-use=\"${LLVM_SPROFDATA_FILE}\""
CMAKE_CXX_FLAGS
CMAKE_C_FLAGS)
if(NOT LINKER_IS_LLD_LINK)
append("-fpseudo-probe-for-profiling -fprofile-sample-use=\"${LLVM_SPROFDATA_FILE}\""
CMAKE_EXE_LINKER_FLAGS
CMAKE_SHARED_LINKER_FLAGS)
endif()
else()
message(FATAL_ERROR "LLVM_SPROFDATA_FILE can only be specified when compiling with clang")
endif()
endif()
option(LLVM_BUILD_INSTRUMENTED_COVERAGE "Build LLVM and tools with Code Coverage instrumentation" Off)
option(LLVM_INDIVIDUAL_TEST_COVERAGE "Emit individual coverage file for each test case." OFF)
mark_as_advanced(LLVM_BUILD_INSTRUMENTED_COVERAGE)