I want to evaluate an AVX2 program written in c-intrinsics using gcc 5.4.0 and clang 3.8 for compiling and using perf , valgrind and IACA for evaluating and analysis. I Exactly want the same optimization approach so I read this related question clang optimization and this page for gcc optimization option for gcc but I still doubted .
gcc -O2 and gcc -O3 is my basis and want the same in clang since Clang do auto-vectorization in -O2 and I don't want it when comparing the results with gcc -O2 and want it when -O3 is enabled in gcc. so the question is what command should I use in clang that is corresponded to these commands in gcc :
First:
compile :
gcc -Wall -O2 -march=native -masm=intel -c -S "%f"
build:
gcc -Wall -O2 -mavx2 -o "%e" "%f"
Second:
compile :
gcc -Wall -O3 -march=native -masm=intel -c -S "%f"
build:
gcc -Wall -O3 -mavx2 -o "%e" "%f"
Related
How to do in clang the gcc -O optimizing option equivalent?
gcc -O3 -o tes tes.cpp
on clang ...?
You do exactly the same.
clang -O3 -o tes tes.cpp
I am trying to compile FormCalc 9.9 on a MacOS 10.10.5.
Compilation consists in running a bash script on terminal. I redirect both stdout and sterr to a log file, but this is all the output I get:
$ ./compile
Compiling for system type MacOSX-x86-64
cp -p ./bin/MacOSX-x86-64/* MacOSX-x86-64/
gcc -O3 -fomit-frame-pointer -ffast-math -Wall -Wextra -m64 -o MacOSX-x86-64/ToForm ./FormCalc/ToForm.c
./FormCalc/ToForm.c:72:9: warning: declaration does not declare anything [-Wmissing-declarations]
__attribute__ ((fallthrough));
^
>
1 warning generated.
strip MacOSX-x86-64/ToForm
gcc -O3 -fomit-frame-pointer -ffast-math -Wall -Wextra -m64 -o MacOSX-x86-64/ToFortran ./FormCalc/ToFortran.c
strip MacOSX-x86-64/ToFortran
gcc -O3 -fomit-frame-pointer -ffast-math -Wall -Wextra -m64 -o MacOSX-x86-64/ToC ./FormCalc/ToC.c
strip MacOSX-x86-64/ToC
gcc -O3 -fomit-frame-pointer -ffast-math -Wall -Wextra -m64 -o MacOSX-x86-64/reorder ./tools/reorder.c
strip MacOSX-x86-64/reorder
looking for gcc... /usr/bin/clang
looking for g++... /usr/bin/clang++
looking for fortran... /usr/local/bin/gfortran
extracting the Fortran libraries... ok
does gfortran append underscores... error linking Fortran and C
How can I get more information about the linking error?
I have converted c program into assembly code using following commands in LLVM :
clang -emit-llvm matrix.c -c -o matrix.bc
llc -march=alpha matrix.bc -o matrix.s
Now how to convert matrix.s assembly file into executable file of alpha.
How to do that?
clang can also be used
clang matrix.s -L [additional library locations] -mllvm -Wall -g -L. -Wl,-pie -I. -I[additional include locations] -o [executable output]
Adjust the flags as your needs dictate.
EDIT
Without the need for other includes or libraries just call:
clang matrix.s -mllvm -Wall -g -Wl,-pie -o matrix.out
gcc experts,
I'm trying to use gcc lto with library archives, as the gcc comes with my system (RedHat Enterprise Linux 5.7) doesn't work with -flto (neither for my Ubuntu 14.10), so I build binutils && gcc from scratch.
Here is what I did:
1. Build binutils-2.22 with --enable-plugins
2. Build gcc-4.7.2 with --with-plugin-ld=/path/to/ld/built/in/step1 --enable-lto
3. Then for the following simple test:
// 1.c:
int foo(void)
{ return 0; }
// 2.c:
extern int foo(void)
int main(void)
{ return foo(); }
The following can get foo() inlined:
my_gcc -O3 -flto -c -o 1.o 1.c
my_gcc -O3 -flto -c -o 2.o 2.c
my_gcc -O3 -flto -o a.out 1.o 2.o
While the following can't:
my_gcc -O3 -flto -c -o 1.o 1.c
my_gcc -O3 -flto -c -o 2.o 2.c
my_ar cr --plugin <my_gcc>/libexec/gcc/x86_64-redhat-linux/4.7.2/liblto_plugin.so 1.a 1.o
my_ar cr --plugin <my_gcc>/libexec/gcc/x86_64-redhat-linux/4.7.2/liblto_plugin.so 2.a 2.o
gcc -O3 -flto -fuse-linker-plugin -o a.out 1.a 2.a
As the building system for the product I'm working on has to use archives, then what I can do to let lto work with library archive?
Your help will be much much appreciated.
Thanks a lot.
When linking, the order in which the libraries are listed on the command line, matters. So when compiling from the archives, you should swap 1.a and 2.a:
gcc -O3 -flto -fuse-linker-plugin -o a.out 2.a 1.a
I tested with gcc 4.9.2 and the disassembly, obtained with objdump -d a.out, shows that foo() is being inlined.
I am using the Boost library in Unix, GCC. I read the following topic: Boost static linking and added -static to my Makefile. However, this does not work.
Here is my Makefile:
all: nbbo
nbbo: nbbo.o reader.o
g++ -static -O3 -ffast-math -funroll-loops -ansi -pedantic-errors -L/usr/lib -lboost_filesystem -lboost_serialization -lboost_iostreams -lz -I /usr/include/boost -o nbbo nbbo.o reader.o
nbbo.o: nbbo.cpp
g++ -static -O3 -ffast-math -funroll-loops -ansi -pedantic-errors -I /usr/include/boost -c -o nbbo.o nbbo.cpp
reader.o: reader.cc reader.h
g++ -static -O3 -ffast-math -funroll-loops -ansi -pedantic-errors -I /usr/include/boost -c -o reader.o reader.cc
clean:
rm *.o
And here is the error message:
nbbo.o: In function `__tcf_10':
nbbo.cpp:(.text+0x3d9): undefined reference to `boost::serialization::extended_type_info::key_unregister() const'
nbbo.cpp:(.text+0x3e3): undefined reference to `boost::serialization::typeid_system::extended_type_info_typeid_0::type_unregister()'
nbbo.cpp:(.text+0x3fb): undefined reference to `boost::serialization::typeid_system::extended_type_info_typeid_0::~extended_type_info_typeid_0()'
etc
Which "UNIX" are you using? Using the -static flag should work fine on linux. But not on OSX. On OSX you have to remove the static flag and give the complete path to the library in order to link statically. I dont know how this would work on other "UNIXes"
eg.
g++ ..... /path/to/your/lib.a ... -o ..