Lines Matching +full:- +full:dllvm_enable_projects
11 large applications measuring over hundreds of megabytes in size. However, medium-sized
12 programs can benefit too. Clang, one of the most popular open-source C/C++ compilers,
15 misses and can be significantly improved with BOLT, even on top of profile-guided and
16 link-time optimizations.
20 the compile-time performance gains are coming from, and verify that the speed-ups are
27 on how to obtain and build Clang in [Bootstrapping Clang-7 with PGO and LTO](#bootstrapping-clang-7-with-pgo-and-lto) section.
29 The only difference from the standard Clang build is that we require the `-Wl,-q` flag to be present during
35 We will use the setup described in [Bootstrapping Clang-7 with PGO and LTO](#bootstrapping-clang-7-with-pgo-and-lto).
36 Adjust the steps accordingly if you skipped that section. We will also assume that `llvm-bolt` is present in your `$PATH`.
41 implements taken branch sampling (`-b/-j` flag). For that reason, it may not be possible to
49 $ CPATH=${TOPLEV}/stage2-prof-use-lto/install/bin/
50 $ cmake -G Ninja ${TOPLEV}/llvm -DLLVM_TARGETS_TO_BUILD=X86 -DCMAKE_BUILD_TYPE=Release \
51 -DCMAKE_C_COMPILER=$CPATH/clang -DCMAKE_CXX_COMPILER=$CPATH/clang++ \
52 -DLLVM_ENABLE_PROJECTS="clang" \
53 -DLLVM_USE_LINKER=lld -DCMAKE_INSTALL_PREFIX=${TOPLEV}/stage3/install
54 $ perf record -e cycles:u -j any,u -- ninja clang
61 $ perf2bolt $CPATH/clang-7 -p perf.data -o clang-7.fdata -w clang-7.yaml
63 Notice that we are passing `clang-7` to `perf2bolt` which is the real binary that
67 $ llvm-bolt $CPATH/clang-7 -o $CPATH/clang-7.bolt -b clang-7.yaml \
68 -reorder-blocks=ext-tsp -reorder-functions=hfsort+ -split-functions \
69 -split-all-cold -dyno-stats -icf=1 -use-gnu-stack
74 BOLT-INFO: enabling relocation mode
75 BOLT-INFO: 11415 functions out of 104526 simple functions (10.9%) have non-empty execution profile.
77 BOLT-INFO: ICF folded 29144 out of 105177 functions in 8 passes. 82 functions had jump tables.
78 BOLT-INFO: Removing all identical functions will save 5466.69 KB of code space. Folded functions were called 2131985 times based on profile.
79 BOLT-INFO: basic block reordering modified layout of 7848 (10.32%) functions
81 660155947 : executed forward branches (-2.3%)
82 48252553 : taken forward branches (-57.2%)
84 52389551 : taken backward branches (-19.5%)
85 35650038 : executed unconditional branches (-33.2%)
89 6113398840 : executed instructions (-0.6%)
93 825703946 : total branches (-2.1%)
94 136292142 : taken branches (-41.1%)
95 689411804 : non-taken conditional branches (+12.6%)
96 100642104 : taken conditional branches (-43.4%)
104 ## Measuring Compile-time Improvement
106 `clang-7.bolt` can be used as a replacement for *PGO+LTO* Clang:
108 $ mv $CPATH/clang-7 $CPATH/clang-7.org
109 $ ln -fs $CPATH/clang-7.bolt $CPATH/clang-7
112 build time reduction on a 48-core Haswell system:
114 $ ln -fs $CPATH/clang-7.org $CPATH/clang-7
115 $ ninja clean && /bin/time -f %e ninja clang -j48
117 $ ln -fs $CPATH/clang-7.bolt $CPATH/clang-7
118 $ ninja clean && /bin/time -f %e ninja clang -j48
132 $ ln -fs $CPATH/clang-7.org $CPATH/clang-7
133 $ ninja clean && perf stat -e instructions,L1-icache-misses -- ninja clang -j48
136 359,996,216,537 L1-icache-misses
142 $ ln -fs $CPATH/clang-7.bolt $CPATH/clang-7
143 $ ninja clean && perf stat -e instructions,L1-icache-misses -- ninja clang -j48
146 244,888,677,972 L1-icache-misses
149 the number of stalls in the CPU front-end.
157 the compilation of other projects? We picked `mysqld`, an open-source database, to do the test.
159 On our 48-core Haswell system using the *PGO+LTO* Clang, the build finished in 136.06 seconds, while using the *PGO+LTO+BOLT* Clang, 126.10 seconds.
168 using the `merge-fdata` utility that comes with BOLT. Optimized with that profile, the *PGO+LTO+BOLT* Clang was able
181 ----
184 ## Bootstrapping Clang-7 with PGO and LTO
188 except for the last step that adds `-Wl,-q` linker flag to the final build.
190 ### Getting Clang-7 Sources
193 builds. E.g. `TOPLEV=~/clang-7/`. Follow with commands to clone the `release_70`
198 $ git clone --branch=release/7.x https://github.com/llvm/llvm-project.git
208 compiler-rt components that are known to cause build issues at release/7.x.
212 $ cmake -G Ninja ${TOPLEV}/llvm-project/llvm -DLLVM_TARGETS_TO_BUILD=X86 \
213 -DCMAKE_BUILD_TYPE=Release \
214 -DCMAKE_C_COMPILER=gcc -DCMAKE_CXX_COMPILER=g++ -DCMAKE_ASM_COMPILER=gcc \
215 -DLLVM_ENABLE_PROJECTS="clang;lld" \
216 -DLLVM_ENABLE_RUNTIMES="compiler-rt" \
217 -DCOMPILER_RT_BUILD_SANITIZERS=OFF -DCOMPILER_RT_BUILD_XRAY=OFF \
218 -DCOMPILER_RT_BUILD_LIBFUZZER=OFF \
219 -DCMAKE_INSTALL_PREFIX=${TOPLEV}/stage1/install
225 Using the freshly-baked stage 1 Clang compiler, we are going to build Clang with
228 $ mkdir ${TOPLEV}/stage2-prof-gen
229 $ cd ${TOPLEV}/stage2-prof-gen
231 $ cmake -G Ninja ${TOPLEV}/llvm-project/llvm -DLLVM_TARGETS_TO_BUILD=X86 \
232 -DCMAKE_BUILD_TYPE=Release \
233 -DCMAKE_C_COMPILER=$CPATH/clang -DCMAKE_CXX_COMPILER=$CPATH/clang++ \
234 -DLLVM_ENABLE_PROJECTS="clang;lld" \
235 -DLLVM_USE_LINKER=lld -DLLVM_BUILD_INSTRUMENTED=ON \
236 -DCMAKE_INSTALL_PREFIX=${TOPLEV}/stage2-prof-gen/install
246 $ mkdir ${TOPLEV}/stage3-train
247 $ cd ${TOPLEV}/stage3-train
248 $ CPATH=${TOPLEV}/stage2-prof-gen/install/bin
249 $ cmake -G Ninja ${TOPLEV}/llvm-project/llvm -DLLVM_TARGETS_TO_BUILD=X86 \
250 -DCMAKE_BUILD_TYPE=Release \
251 -DCMAKE_C_COMPILER=$CPATH/clang -DCMAKE_CXX_COMPILER=$CPATH/clang++ \
252 -DLLVM_ENABLE_PROJECTS="clang" \
253 -DLLVM_USE_LINKER=lld -DCMAKE_INSTALL_PREFIX=${TOPLEV}/stage3-train/install
257 `${TOPLEV}/stage2-prof-gen/profiles`. We will merge them before they can be
260 $ cd ${TOPLEV}/stage2-prof-gen/profiles
261 $ ${TOPLEV}/stage1/install/bin/llvm-profdata merge -output=clang.profdata *
267 our scenario, i.e. building Clang. We will also enable link-time optimizations
268 to allow cross-module inlining and other optimizations. Finally, we are going to
274 $ mkdir ${TOPLEV}/stage2-prof-use-lto
275 $ cd ${TOPLEV}/stage2-prof-use-lto
277 $ export LDFLAGS="-Wl,-q"
278 $ cmake -G Ninja ${TOPLEV}/llvm-project/llvm -DLLVM_TARGETS_TO_BUILD=X86 \
279 -DCMAKE_BUILD_TYPE=Release \
280 -DCMAKE_C_COMPILER=$CPATH/clang -DCMAKE_CXX_COMPILER=$CPATH/clang++ \
281 -DLLVM_ENABLE_PROJECTS="clang;lld" \
282 -DLLVM_ENABLE_LTO=Full \
283 -DLLVM_PROFDATA_FILE=${TOPLEV}/stage2-prof-gen/profiles/clang.profdata \
284 -DLLVM_USE_LINKER=lld \
285 -DCMAKE_INSTALL_PREFIX=${TOPLEV}/stage2-prof-use-lto/install