search for: mrelax

Hi all, clang -O0 currently differs from -O1 and higher in passing down -mrelax-all. When compiling assembler files, this results in conditional jumps using the relaxed forms, which is surprising. Based on the discussion on IRC, I did a llvm/clang release build with -O0 for OPTIMIZER and -O0 -mno-relax-all. Result is: -O0 (-mrelax-all) 68m27.893s 254m19.920s 1m45.720s -O0 -...

...06d407508653c2cbd270a1a51c) (https://github.com/llvm-mirror/llvm 943496ffc4e7cb9d7dd6f5119325a7583e2cc31f) Target: x86_64-pc-linux-musl Thread model: posix InstalledDir: /path/to/llvm/bin "/path/to/musl/lib/ld-musl-x86_64.so.1" -cc1 -triple x86_64-pc-linux-musl -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name hello.c -mrelocation-model static -mthread-model posix -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -target-cpu x86-64 -v -dwarf-column-info -debugger-tuning=gdb -coverage-notes-file...

....sh --- # Crash reproducer for clang version 10.0.0 # Driver args: "-c" "-m64" "crash.c" # Original command: "C:\\Program Files\\LLVM\\bin\\clang.exe" "-cc1" "-triple" "x86_64-pc-windows-msvc19.11.0" "-emit-obj" "-mrelax-all" "-mincremental-linker- compatible" "-disable-free" "-disable-llvm-verifier" "-discard-value-names" "-ma in-file-name" "crash.c" "-mrelocation-model" "pic" "-pic-level" "2" "-mthread-mo...

On Tue, Jun 3, 2014 at 7:59 AM, Nancy <nancydreaming at gmail.com> wrote: >> First, you could switch to ld.gold instead of ld.bfd. It uses much > $ln -s `which gold` /usr/local/bin/ld > >> the idea. I think for autoconf you need ".../configure >> --enable-split-dwarf" to use this. >> > $.../configure --enable-targets=x86 --enable-split-dwarf >

...version 10.0.0 >> # Driver args: "-c" "-m64" "crash.c" >> # Original command: "C:\\Program Files\\LLVM\\bin\\clang.exe" "-cc1" >> "-triple" >> "x86_64-pc-windows-msvc19.11.0" "-emit-obj" "-mrelax-all" >> "-mincremental-linker- >> compatible" "-disable-free" "-disable-llvm-verifier" >> "-discard-value-names" "-ma >> in-file-name" "crash.c" "-mrelocation-model" "pic" "-pic-level&q...

> E.g. -mrelax-all is either harmful or not improving enough to give a > measurable improvement. > > Can someone else try to reproduce this? I can. I tried these builds on tmpfs so as to give -mno-relax-all an smaller advantaged for less IO: --enable-optimized --with-optimize-option=-O0 real 3m38.568s...

> > It's more of a debugging tool and stress test of the x86 branch relaxation than anything. It's definitely not intended to be an optimization. > > "relax-all" says to not just relax instructions that are strictly required, but to relax every instruction that can be relaxed, whether it's needed or not. > > I'm more inclined to remove the command line

...t would be very reasonable > since at this point I assume the MC assembler is considered to be > stable. I think you are right about it being an optimization (compile time optimization to be precise). In fact, it is used by default at -O0, run "clang -c test.c -v" and you will see -mrelax-all being passed, but not if you add -O1. It is not used on optimized builds because it produces larger binaries. > Eli Cheers, Rafael

...: error: unable to execute command: Aborted unsupported GC: vmkit UNREACHABLE executed at GCMetadata.cpp:87! 0 clang 0x09e9d5d9 llvm::sys::PrintStackTrace(_IO_FILE*) + 41 Stack dump: 0. Program arguments: /home/ali/llvm-3.3.src/Release+Asserts/bin/clang -cc1 -triple i386-pc-linux-gnu -emit-obj -mrelax-all -disable-free -main-file-name somefile.bc -mrelocation-model static -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases -target-cpu pentium4 -target-linker-version 2.21.53.20110810 -resource-dir /home/ali/llvm-3.3.src/Release+Asserts/bin/../lib/clang/3.3 -fdebug-compilation-dir /...

...Driver args: "-c" "-m64" "crash.c" >> >> # Original command: "C:\\Program Files\\LLVM\\bin\\clang.exe" "-cc1" >> >> "-triple" >> >> "x86_64-pc-windows-msvc19.11.0" "-emit-obj" "-mrelax-all" >> >> "-mincremental-linker- >> >> compatible" "-disable-free" "-disable-llvm-verifier" >> >> "-discard-value-names" "-ma >> >> in-file-name" "crash.c" "-mrelocation-model&quot...

...7dd63c8d742250dac6ea365e7c30f0fbab3257) Target: avr Thread model: posix InstalledDir: /usr/local/bin Found candidate GCC installation: /usr/lib/gcc/avr/5.4.0 Selected GCC installation: /usr/lib/gcc/avr/5.4.0 (in-process) "/usr/local/bin/clang-11" -cc1 -triple avr -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name main.cpp -mrelocation-model static -mthread-model posix -mframe-pointer=all -fmath-errno -fno-rounding-math -masm-verbose -mconstructor-aliases -target-cpu atmega328p -dwarf-column-info -fno-split-dwarf-inlining -debugger...

...nd: "/Users/user/workspace/github/clang_build/manual/llvm-project/_install/Toolchains/LLVM12.0.0git.xctoolchain/usr/bin/clang-12" -cc1 -triple x86_64-apple-macosx10.15.0 -Wundef-prefix=TARGET_OS_ -Werror=undef-prefix -Wdeprecated-objc-isa-usage -Werror=deprecated-objc-isa-usage -emit-obj -mrelax-all --mrelax-relocations -disable-free -main-file-name seq_vector.cpp -mrelocation-model pic -pic-level 2 -mframe-pointer=all -fno-rounding-math -munwind-tables -target-sdk-version=10.15.6 -fcompatibility-qualified-id-block-type-checking -fvisibility-inlines-hidden-static-local-var -target-cpu penr...

On Feb 25, 2011, at 11:38 AM, Rafael Avila de Espindola wrote: >>> Can someone else try to reproduce this? > > I tried gcc.c from > http://people.csail.mit.edu/smcc/projects/single-file-programs/ and the > difference is a bit more noticeable: > > -O0 -mno-relax-all > > real 0m13.182s > user 0m12.690s > sys 0m0.450s > > -O0 > > gcc.o is

Hello, In llc, we have this flag (output of command --help | grep relax): -mc-relax-all - When used with filetype=obj, relax all fixups in the emitted object file It also appears in clang: -mrelax-all (integrated-as) Relax all machine instructions I'd like to discuss the naming and semantics of this flag, because ISTM at least the name is misleading. If I understand correctly, relaxation is always required in MC (*) to produce correct code, and in fact MC always performs relaxati...

>> Can someone else try to reproduce this? I tried gcc.c from http://people.csail.mit.edu/smcc/projects/single-file-programs/ and the difference is a bit more noticeable: -O0 -mno-relax-all real 0m13.182s user 0m12.690s sys 0m0.450s -O0 gcc.o is 10932968 bytes. real 0m12.969s user 0m12.520s sys 0m0.410s gcc.o is 11410552 bytes IMHO it would still be reasonable to switch to

....9.3 Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8 Candidate multilib: .;@m64 Candidate multilib: 32;@m32 Candidate multilib: x32;@mx32 Selected multilib: .;@m64 "/usr/local/google/home/dberris/xray/llvm-build/bin/clang-3.9" -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -mrelax-all -disable-free -main-file-name test.cc -mrelocation-model static -mthread-model posix -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -v -dwarf-column-info -debug-info-kind=limited -dwarf-version=4 -debugger-tuning=gdb -fxray...

...compiler verbose option "-v". It will show you how exactly clang invokes the backend: > clang -v -c showdebug.c clang version 3.2 (trunk 156703) Target: x86_64-unknown-linux-gnu Thread model: posix "/opt/kernelgen/bin/clang" -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -mrelax-all -disable-free -main-file-name showdebug.c -mrelocation-model static -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -target-cpu x86-64 -target-linker-version 11 -momit-leaf-frame-pointer -v -coverage-file showdebug.o -resource-dir /opt/kernelgen/bin/../lib/cla...

...x00000000006d2b27 main + 7175 17 libc.so.6 0x00007fe8a0857c4d __libc_start_main + 253 18 clang 0x00000000006c7bc9 Stack dump: 0. Program arguments: /usr/local/google/tsan-llvm/data-race-test/clang_build_Linux/Release+Asserts/bin/clang -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -mrelax-all -disable-free -main-file-name t.c -mrelocation-model static -mdisable-fp-elim -masm-verbose -mconstructor-aliases -munwind-tables -target-cpu x86-64 -target-linker-version 2.20.1 -momit-leaf-frame-pointer -coverage-file t.o -resource-dir /usr/local/google/tsan-llvm/data-race-test/clang_build_Li...

...0x000000010001d2cd main + 765 32 clang 0x0000000100018c64 start + 52 33 clang 0x0000000000000021 start + 4294865905 Stack dump: 0. Program arguments: /Volumes/MacPro/Projects/OpenSource/llvm/release/Release+Asserts/bin/clang -cc1 -triple i386-apple-darwin10.0.0 -emit-obj -mrelax-all -disable-free -main-file-name round.c -pic-level 1 -mdisable-fp-elim -masm-verbose -target-cpu yonah -target-linker-version 97.14 -resource-dir /Volumes/MacPro/Projects/OpenSource/llvm/release/Release+Asserts/lib/clang/2.9 -ferror-limit 19 -fmessage-length 180 -stack-protector 1 -fblocks -fdiag...

Hi Jack, Are you packaging all the static libraries that lld produces as part of the package ? PS : When I build on x86_64, I only get a 9M image for lld. Thanks Shankar Easwaran On 11/20/2013 9:15 AM, Jack Howarth wrote: > When lld-3.4 is added to the tools directory of the llvm source tree > as lld, the resulting cmake build produces a huge number of static libs and > bloats