MaskRay added a comment. In D120305#3344938 <https://reviews.llvm.org/D120305#3344938>, @nikic wrote:
> Hm, it looks like enabling PIE has a pretty big negative compile-time impact, > with a 20% regression on sqlite3: > http://llvm-compile-time-tracker.com/compare.php?from=611122892e6d5813444bdd0e1fbe0a96f6e09779&to=3c4ed02698afec021c6bca80740d1e58e3ee019e&stat=instructions > Code-size on kimwitu++ regresses by 13%. > > Is that kind of impact expected? Many groups build sqlite3 with -fPIC. -fPIC and -fPIE have similar compile time. The metric on llvm-compile-time-tracker.com is related to `llvm-test-suite/CTMark/sqlite3`, which just focuses on (without the CMake patch) `-fno-pic` performance. ( I checked run time, no big difference. % hyperfine --warmup 2 --min-runs 16 "/tmp/c/sqlite3.nopie -init sqlite3rc :memory: < commands" Benchmark 1: /tmp/c/sqlite3.nopie -init sqlite3rc :memory: < commands Time (mean ± σ): 2.068 s ± 0.011 s [User: 2.044 s, System: 0.024 s] Range (min … max): 2.044 s … 2.085 s 16 runs % hyperfine --warmup 2 --min-runs 16 "/tmp/c/sqlite3.pie -init sqlite3rc :memory: < commands" Benchmark 1: /tmp/c/sqlite3.pie -init sqlite3rc :memory: < commands Time (mean ± σ): 2.053 s ± 0.015 s [User: 2.034 s, System: 0.018 s] Range (min … max): 2.027 s … 2.080 s 16 runs ) About compile time, I run `=time -f "CPU: %Us\tReal: %es\tRAM: %MKB" /tmp/out/custom1/bin/clang -DNDEBUG -O3 -DNDEBUG -w -Werror=date-time -DSTDC_HEADERS=1 -DHAVE_SYS_TYPES_H=1 -DHAVE_SYS_STAT_H=1 -DHAVE_STDLIB_H=1 -DHAVE_STRING_H=1 -DHAVE_MEMORY_H=1 -DHAVE_STRINGS_H=1 -DHAVE_INTTYPES_H=1 -DHAVE_STDINT_H=1 -DHAVE_UNISTD_H=1 -DSQLITE_OMIT_LOAD_EXTENSION=1 -DSQLITE_THREADSAFE=0 -I. -o CTMark/sqlite3/CMakeFiles/sqlite3.dir/sqlite3.c.o -c ~/Dev/llvm-test-suite/CTMark/sqlite3/sqlite3.c -ftime-report` with -fno-pie/-fpie/-fpic to get some insight. The IR has minor difference but pie's is slightly larger: % wc -l nopie.ll pie.ll 157975 nopie.ll 159675 pie.ll ... If someone wants to investigate, `sqlite3Parser` changes a lot from -fno-pic to -fPIE, but that looks organic changes to me. -ftime-report comparison suggests that every pass is slightly slower with -fPIE. ModuleInlinerWrapperPass and DevirtSCCRepeatedPass contribute most of the slowness. -fno-pic -ftime-report ---User Time--- --System Time-- --User+System-- ---Wall Time--- --- Name --- 5.1753 ( 28.1%) 0.2359 ( 27.5%) 5.4112 ( 28.0%) 5.4123 ( 28.1%) ModuleInlinerWrapperPass 5.1447 ( 27.9%) 0.2309 ( 26.9%) 5.3755 ( 27.8%) 5.3767 ( 27.9%) DevirtSCCRepeatedPass 1.8716 ( 10.1%) 0.0936 ( 10.9%) 1.9652 ( 10.2%) 1.9613 ( 10.2%) InstCombinePass 0.7674 ( 4.2%) 0.0254 ( 3.0%) 0.7928 ( 4.1%) 0.7921 ( 4.1%) GVNPass 0.4563 ( 2.5%) 0.0288 ( 3.4%) 0.4851 ( 2.5%) 0.4844 ( 2.5%) InlinerPass 0.4194 ( 2.3%) 0.0174 ( 2.0%) 0.4368 ( 2.3%) 0.4359 ( 2.3%) MemorySSAAnalysis 0.3399 ( 1.8%) 0.0191 ( 2.2%) 0.3589 ( 1.9%) 0.3578 ( 1.9%) SimplifyCFGPass 0.3206 ( 1.7%) 0.0143 ( 1.7%) 0.3349 ( 1.7%) 0.3354 ( 1.7%) BlockFrequencyAnalysis 0.2985 ( 1.6%) 0.0081 ( 0.9%) 0.3065 ( 1.6%) 0.3061 ( 1.6%) CorrelatedValuePropagationPass 0.2608 ( 1.4%) 0.0158 ( 1.8%) 0.2767 ( 1.4%) 0.2763 ( 1.4%) EarlyCSEPass -fpie -ftime-report ---User Time--- --System Time-- --User+System-- ---Wall Time--- --- Name --- 7.8109 ( 29.2%) 0.2239 ( 26.8%) 8.0347 ( 29.1%) 8.0363 ( 29.2%) ModuleInlinerWrapperPass 7.7752 ( 29.1%) 0.2230 ( 26.6%) 7.9981 ( 29.0%) 7.9997 ( 29.0%) DevirtSCCRepeatedPass 2.5352 ( 9.5%) 0.0807 ( 9.6%) 2.6158 ( 9.5%) 2.6114 ( 9.5%) InstCombinePass 1.2792 ( 4.8%) 0.0162 ( 1.9%) 1.2954 ( 4.7%) 1.2948 ( 4.7%) GVNPass 0.6529 ( 2.4%) 0.0157 ( 1.9%) 0.6686 ( 2.4%) 0.6674 ( 2.4%) MemorySSAAnalysis 0.6048 ( 2.3%) 0.0261 ( 3.1%) 0.6309 ( 2.3%) 0.6306 ( 2.3%) InlinerPass 0.4625 ( 1.7%) 0.0126 ( 1.5%) 0.4751 ( 1.7%) 0.4743 ( 1.7%) CorrelatedValuePropagationPass 0.4541 ( 1.7%) 0.0160 ( 1.9%) 0.4701 ( 1.7%) 0.4690 ( 1.7%) SimplifyCFGPass 0.3981 ( 1.5%) 0.0124 ( 1.5%) 0.4105 ( 1.5%) 0.4101 ( 1.5%) EarlyCSEPass - -fno-pie: Time (mean ± σ): 11.999 s ± 0.043 s - -fpie: Time (mean ± σ): 14.643 s ± 0.073 s - -fno-pie -flegacy-pass-manager: Time (mean ± σ): 16.831 s ± 0.027 s - -fpie -flegacy-pass-manager: Time (mean ± σ): 16.887 s ± 0.099 s Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D120305/new/ https://reviews.llvm.org/D120305 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
