[clang] [Clang][perf-training] Do build of libLLVMSupport for perf training (PR #111625)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Tom Stellard (tstellar)

<details>
<summary>Changes</summary>

This adds a build of the libLLVMSupport to the lit suite that is used for generating profile data.  This helps to improve both PGO and BOLT optimization of clang over the existing hello world training program.

I considered building all of LLVM instead of just libLLVMSupport, but there is only a marginal increase in performance for PGO only builds when training with a build of all of LLVM, and I didn't think it was enough to justify the increased build times given that it is the default configuration.

The benchmark[1] I did showed that using libLLVMSupport for training gives a 1.35 +- 0.02 speed up for clang optimized with PGO + BOLT vs just 1.05 +- 0.01 speed up when training with hello world.

For comparison, training with a full LLVM build gave a speed up of 1.35 +- 0.1.

Raw data:

| PGO Training | BOLT Training | Speed Up | Error Range |
| ------------ | ------------- | -------- | ----------- |
| LLVM Support | LLVM Support  | 1.35     | 0.02        |
| LLVM All     | LLVM All      | 1.34     | 0.01        |
| LLVM Support | Hello World   | 1.29     | 0.02        |
| LLVM All     | PGO-ONLY      | 1.27     | 0.02        |
| LLVM Support | PGO-ONLY      | 1.22     | 0.02        |
| Hello World  | Hello World   | 1.05     | 0.01        |
| Hello World  | PGO-ONLY      | 1.03     | 0.01        |

[1] Benchmark was compiling SemaDecl.cpp

---
Full diff: https://github.com/llvm/llvm-project/pull/111625.diff


5 Files Affected:

- (modified) clang/utils/perf-training/bolt.lit.cfg (+3) 
- (modified) clang/utils/perf-training/bolt.lit.site.cfg.in (+3) 
- (modified) clang/utils/perf-training/lit.cfg (+5-1) 
- (modified) clang/utils/perf-training/lit.site.cfg.in (+3) 
- (added) clang/utils/perf-training/llvm-support/build.test (+2) 


``````````diff
diff --git a/clang/utils/perf-training/bolt.lit.cfg b/clang/utils/perf-training/bolt.lit.cfg
index 0e81a5501e9fcf..1d0cf9a8a17a8e 100644
--- a/clang/utils/perf-training/bolt.lit.cfg
+++ b/clang/utils/perf-training/bolt.lit.cfg
@@ -49,3 +49,6 @@ config.substitutions.append(("%clang_cpp", f" {config.clang} --driver-mode=g++ "
 config.substitutions.append(("%clang_skip_driver", config.clang))
 config.substitutions.append(("%clang", config.clang))
 config.substitutions.append(("%test_root", config.test_exec_root))
+config.substitutions.append(('%cmake_generator', config.cmake_generator))
+config.substitutions.append(('%cmake', config.cmake_exe))
+config.substitutions.append(('%llvm_src_dir', config.llvm_src_dir))
diff --git a/clang/utils/perf-training/bolt.lit.site.cfg.in b/clang/utils/perf-training/bolt.lit.site.cfg.in
index 54de12701c1ae9..3de5026e4792ae 100644
--- a/clang/utils/perf-training/bolt.lit.site.cfg.in
+++ b/clang/utils/perf-training/bolt.lit.site.cfg.in
@@ -11,6 +11,9 @@ config.python_exe = "@Python3_EXECUTABLE@"
 config.clang_obj_root = path(r"@CLANG_BINARY_DIR@")
 config.clang_bolt_mode = "@CLANG_BOLT@"
 config.clang_bolt_name = "@CLANG_BOLT_INSTRUMENTED@"
+config.cmake_exe = "@CMAKE_COMMAND@"
+config.llvm_src_dir ="@CMAKE_SOURCE_DIR@"
+config.cmake_generator ="@CMAKE_GENERATOR@"
 
 # Let the main config do the real work.
 lit_config.load_config(config, "@CLANG_SOURCE_DIR@/utils/perf-training/bolt.lit.cfg")
diff --git a/clang/utils/perf-training/lit.cfg b/clang/utils/perf-training/lit.cfg
index 0bd06c0d44f650..b4527c602fc484 100644
--- a/clang/utils/perf-training/lit.cfg
+++ b/clang/utils/perf-training/lit.cfg
@@ -34,8 +34,12 @@ config.test_format = lit.formats.ShTest(use_lit_shell == "0")
 config.substitutions.append( ('%clang_cpp_skip_driver', ' %s %s %s ' % (cc1_wrapper, config.clang, sysroot_flags)))
 config.substitutions.append( ('%clang_cpp', ' %s --driver-mode=g++ %s ' % (config.clang, sysroot_flags)))
 config.substitutions.append( ('%clang_skip_driver', ' %s %s %s ' % (cc1_wrapper, config.clang, sysroot_flags)))
-config.substitutions.append( ('%clang', ' %s %s ' % (config.clang, sysroot_flags) ) )
+config.substitutions.append( ('%clang', '%s %s ' % (config.clang, sysroot_flags) ) )
 config.substitutions.append( ('%test_root', config.test_exec_root ) )
+config.substitutions.append( ('%cmake_generator', config.cmake_generator ) )
+config.substitutions.append( ('%cmake', config.cmake_exe ) )
+config.substitutions.append( ('%llvm_src_dir', config.llvm_src_dir ) )
 
+print(config.substitutions)
 config.environment['LLVM_PROFILE_FILE'] = 'perf-training-%4m.profraw'
 
diff --git a/clang/utils/perf-training/lit.site.cfg.in b/clang/utils/perf-training/lit.site.cfg.in
index fae93065a4edf2..9d279d552919ac 100644
--- a/clang/utils/perf-training/lit.site.cfg.in
+++ b/clang/utils/perf-training/lit.site.cfg.in
@@ -8,6 +8,9 @@ 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.cmake_exe = "@CMAKE_COMMAND@"
+config.llvm_src_dir ="@CMAKE_SOURCE_DIR@"
+config.cmake_generator ="@CMAKE_GENERATOR@"
 
 # Let the main config do the real work.
 lit_config.load_config(config, "@CLANG_SOURCE_DIR@/utils/perf-training/lit.cfg")
diff --git a/clang/utils/perf-training/llvm-support/build.test b/clang/utils/perf-training/llvm-support/build.test
new file mode 100644
index 00000000000000..f29a594c846869
--- /dev/null
+++ b/clang/utils/perf-training/llvm-support/build.test
@@ -0,0 +1,2 @@
+RUN: %cmake -G %cmake_generator -B %t -S %llvm_src_dir -DCMAKE_C_COMPILER=%clang -DCMAKE_CXX_COMPILER=%clang -DCMAKE_CXX_FLAGS="--driver-mode=g++" -DCMAKE_BUILD_TYPE=Release
+RUN: %cmake --build %t -v --target LLVMSupport

``````````

</details>


https://github.com/llvm/llvm-project/pull/111625