Does the objective-c compiler in Xcode know better, or is it faster if I use bit shift for multiplications and divisions by powers of 2?
NSInteger parentIndex = index >> 1; // integer division by 2
Isn't this a bit 1980's? Don't processors run these instructions in the same time these days? I remember back in my 68000 days when a div was 100+ cycles and a shift only 3 or 4... not sure this is the case any more as processors have moved on.
Why don't you get the compiler to generate the assembler file and have a look what it's generating and run some benchmarks.
I found this on the web which may help you... although it's for 'C' I think most of the options will be the same.
Q: How can I peek at the assembly code generated by GCC?
Q: How can I create a file where I can see the C code and its assembly
translation together?
A: Use the -S (note: capital S) switch to GCC, and it will emit the assembly code to a file with a .s extension. For example, the following command:
gcc -O2 -S -c foo.c
will leave the generated assembly code on the file foo.s.
If you want to see the C code together with the assembly it was converted to, use a command line like this:
gcc -c -g -Wa,-a,-ad [other GCC options] foo.c > foo.lst
which will output the combined C/assembly listing to the file foo.lst.
If you need to both get the assembly code and to compile/link the program, you can either give the -save-temps option to GCC (which will leave all the temporary files including the .s file in the current directory), or use the -Wa,aln=foo.s option which instructs the assembler to output the assembly translation of the C code (together with the hex machine code and some additional info) to the file named after the =.
Related
I designed RISCV32IM processor, and I used "riscv32-unknown-elf-gcc" to generate code for testing.
However, the PC(instruction memory address) value and data memory address of the generated code had arbitrary values. I used this command:
riscv32-unknown-elf-gcc -march=rv32im -mabi=ilp32 -nostartfiles test.c
Can I know if I can set the instruction and data memory address I want?
Thanks.
Thank you for answer.
I designed only HW, and this is my first time using the SW tool chain.
Even if my question is rudimentary, please understand.
The figure is the result of the "-v" option.
enter image description here
I can't modify the script file because I use riscv tool chain in DOCKER environment.
So, I tried to copy the script file (elf32lriscv.x), modify it.
I modified it to 0x10000 ==> 0x00000.
The file name of the copied script is "test5.x".
And it was executed as follows.
What am I doing wrong?
enter image description here
The riscv compiler is using the default linker script to place text and date section... .
If you add -v option to your command line riscv32-unknown-elf-gcc -v -march=rv32im -mabi=ilp32 -nostartfiles test.c, you will see the linker script used by collect 2 ( normally it will be -melf32lriscv . you can find the linker script in ${path_to_toolchain}/riscv32-unknown-elf/lib/ldscripts/ (the default one is .x).
You can also use riscv32-unknown-elf-ld --verbose like explained by #Frant. However , you need to be careful if the toolchain was compiled with enable multilib and you compile for rv64 but the default is rv32 or vice versa. It is not the case probably, but to be sure you can specify the arch with -A elf32riscv for an rv32.
To Set the addresses you can create your own linker script or copy and modify the default one. You can only modify the executable start like explained by #Frant or make more modification and place whatever you want where you want.
Once your own linker script ready you can pass it to the linker with -Wl,-T,${own_linker_script }. you command will be riscv32-unknown-elf-gcc -march=rv32im -mabi=ilp32 -nostartfiles test.c -Wl,-T,${own_linker_script }
I have managed to build the Kicad 4.0.6 in Linux Mageia 5.1 with gcc version 4.9.2. I first manually fixed two wxWidgets 3.0.2 header files in the /usr/include/wx-3.0/wx/ directory: regex.h and features.h. Kicad then compiled successfully. With the native wx-3.0 headers, the compiler generated the error in pcbnew/netlist_reader.cpp due to the undefined variable wxRE_ADVANCED.
The features.h header checks if the macro WX_NO_REGEX_ADVANCED is defined. If yes, features.h UNdefines wxHAS_REGEX_ADVANCED macro, and defines it, if no. The macro wxHAS_REGEX_ADVANCED, in turn, is used in regex.h to determine if among the enum constants wxRE_ADVANCED = 1 is present. The standard prebuilt Mageia 5 packages wxgtku3.0_0 and lib64wxgtku3.0-devel that I installed with the use of Mageia's software manager urpmi from Mageia repository WX_NO_REGEX_ADVANCED is defined, therefore wxHAS_REGEX_ADVANCED is undefined, and, hence, wxRE_ADVANCED is undefined either. Kicad 4.0.6 source package assumes wxRE_ADVANCED = 1, therefore the build process stops with the error.
Then I reverted /usr/include/wx-3.0/wx/regex.h and features.h to their original state and learned how to add the definition of wxRE_ADVANCED to CMakeLists.txt. However, I still have a question.
The recommended format of adding the definition to CMakeLists.txt I found at CMake command line for C++ #define is this:
if (NOT DEFINED wxRE_ADVANCED)
set(wxRE_ADVANCED 1)
endif()
add_definitions(-DwxRE_ADVANCED=$(wxRE_ADVANCED))
However, it did not work! The macro expansion for wxRE_ADVANCED in pcbnew/netlist_reader.cpp was empty. I printed it at compile time inserting the following lines into the netlist_reader.cpp file (this was hard to find, most of the recommended formats did not work. The correct one is in C preprocessor: expand macro in a #warning):
#define __STRINGIFY(TEXT) #TEXT
#define __WARNING(TEXT) __STRINGIFY(GCC warning TEXT)
#define WARNING(VALUE) __WARNING(__STRINGIFY(wxRE_ADVANCED = VALUE))
Pragma (WARNING(wxRE_ADVANCED))
Finally, I simplified the CMakeLists.txt definition down to this, and it was a success:
if (NOT DEFINED wxRE_ADVANCED)
set(wxRE_ADVANCED 1)
endif()
add_definitions(-DwxRE_ADVANCED=1)
My question: what is the meaning of "-DwxRE_ADVANCED=$(wxRE_ADVANCED)" if it does not work? Is it possible not to use set(wxRE_ADVANCED 1), and simply write add_definitions(-DwxRE_ADVANCED=1)? Thank you.
P.S. Yes, the Kicad 4.0.6 build process successfully finished with only one line added to the top level CMakeLists.txt file:
add_definitions(-DwxRE_ADVANCED=1)
A variable is called via $variable or ${variable}. Note the curly brackets, not parentheses.
Also, it is recommended to use:
target_compile_definitions(mytarget PUBLIC wxRE_ADVANCED=1)
on a target directly, rather than the general add_definitions() command.
I have cross compiled a software for an HummingBoard-Pro (arm processor).
The software just receives some data using the lcm protocol.
If I use the cross compiled software, the data received by the application are invalid, while if I use on-board compiled software everything works fine.
-The software is exactly the same!
-I cross compiled using cmake and a specific arm toolchain.
Output example of cross compiled sw:
first value 5.73599e+107
second value 5.73599e+107
third value 5.73599e+107
Output example of on board compiled sw:
first value 1
second value 2
third value 3
Note: It's my first cross compilation attempt so probably something goes wrong but I haven't really idea about what.
CMakelists file
cmake_minimum_required(VERSION 3.1)
set(main_project_dir ${CMAKE_CURRENT_SOURCE_DIR})
set(external_dir ${main_project_dir}/external)
set(external_lcm_dir ${external_dir}/lcm_dir)
set(external_lcm ${external_lcm_dir}/lcm)
set(external_lcm_build ${external_lcm}/build)
set(external_lcm_gen_exe /usr/local/bin/lcm-gen)
set(lcm_input_file ${main_project_dir}/lcm_format_files/lcm_input_files/indrive.sensors.vanet.lcm)
set(lcm_libraries ${main_project_dir}/external/lcm_dir/lcm/build/lcm)
set(lmc_libraries_header ${main_project_dir}/external/lcm_dir/lcm/)
set(lcm_autogenerated_dir ${main_project_dir}/build/lcm_autogenerated_classes)
add_custom_target(
generate-lcm
COMMAND ${external_lcm_gen_exe} -x ${lcm_input_file} --cpp-hpath ${lcm_autogenerated_dir}
COMMENT "=================== Generating lcm files..."
)
add_subdirectory(testSender)
add_subdirectory(testReceiver)
TOOLCHAIN FILE
SET (CMAKE_SYSTEM_NAME Linux)
SET (CMAKE_SYSTEM_VERSION 1)
SET (CMAKE_SYSTEM_PROCESSOR arm)
INCLUDE_DIRECTORIES(/usr/hummingboard/usr/include /usr/hummingboard/include /usr/hummingboard/usr/include/arm-linux-gnueabihf/)
LINK_DIRECTORIES(/usr/hummingboard/usr/lib /usr/hummingboard/lib /usr/hummingboard/lib/arm-linux-gnueabihf )
SET(CMAKE_PREFIX_PATH /usr/arm-linux-gnueabihf/lib/
/usr/hummingboard/
/usr/hummingboard/lib/arm-linux-gnueabihf/
/usr/hummingboard/usr
/usr/hummingboard/usr/lib/arm-linux-gnueabihf/
)
SET (CMAKE_C_COMPILER /usr/bin/arm-linux-gnueabi-gcc)
SET (CMAKE_CXX_COMPILER /usr/bin/arm-linux-gnueabi-g++)
SET (CMAKE_FIND_ROOT_PATH /usr/hummingboard/ /usr/hummingboard/usr)
SET (CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
SET (CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
SET (CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)
SET (CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
Turning my comments into an answer
Your toolchain file looks like a mixture of two GNU toolchains, which is not allowed and could explain strange behavior of your software.
I would e.g. expect there to be a /usr/hummingboard/bin directory. And shouldn't there be a arm-linux-gnueabihf-gcc to match with /usr/arm-linux-gnueabihf/lib/.
My guess would be that you are mixing hard-float (hf) with soft-float libraries and native- with cross-compilers.
It gets visible with the value 5.73599e+107 = 0x7f800000 which means infinite.
To find the root-cause I would recommend to check your floating point settings. Please compare the compiler command lines between both builds (working vs. non-working) using verbose makefiles.
References
Assign infinity to float
Using CMake with GNU Make: How can I see the exact commands?
I am working on a project where our verification test scripts need to locate symbol addresses within the build of software being tested. This might be used for setting breakpoints or reading static data from memory. What I am after is to create a map file containing symbol names, base address in memory, and size. Our build outputs an ELF file which has the information I want. I've been trying to use the readelf, nm, and objdump tools to try and to gain the symbol addresses I need.
I originally tried readelf -s file.elf and that seemed to access some symbols, particularly those which were written in assembler. However, many of the symbols that I wanted were not in there - specifically those that originated within our Ada code.
I used readelf --debug-dump file.elf to dump all debug information. From that I do see all symbols, including those that were in the Ada code. However, the format seems to be in the DWARF format. Does anyone know why these symbols would not be output by readelf when I ask it to list the symbolic information? Perhaps there is simply an option I am missing.
Now I could go to the trouble of writing a custom DWARF parser to get the information but if I can get it using one of the Binutils (nm, readelf, objdump) then I'd really like prefer a standard solution.
DWARF is the debug information and tries to reflect the relation of the original source code. Taking following code as an example
static int one() {
// something
return 1;
}
int main(int ac, char **av) {
return one();
}
After you compile it using gcc -O3 -g, the static function one will be inlined into main. So when you use readelf -s, you will never see the symbol one. However, when you use readelf --debug-dump, you can see one is a function which is inlined.
So, in this example, compiler does not prohibit you use optimization with -g, so you can still debug the executable. In that example, even the function is optimized and inlined, gdb still can use DWARF information to know the function and source/line from current code block inside inlined function.
Above is just a case of compiler optimization. There might be plenty of reasons that could lead to mismatch symbols address between readelf -s and DWARF.
I hope the title clarifies what I want to ask because it is a bit tricky.
I have a SCONS SConscript for every subdir as follows (doing it in linux, if it matters):
src_dir
compiler
SConscript
yacc srcs
scripts
legacy_script
data
SConscript
data files for the yacc
I use a variant_dir without copy, for example:
SConscript('src_dir/compiler/SConscript', variant_dir = 'obj_dir', duplicate = 0)
The resulting obj_dir after building the yacc is:
obj_dir
compiler
compiler_compiler.exe
Now here is the deal.
I have another SConscript in the data dir that needs to do 2 things:
1. compile the data with the yacc compiled compiler
2. Take the output of the compiler and run it with the legacy_script I can't change
(the legacy_script, takes the output of the compiled data and build some h files for another software to depend on)
number 1 is acheived easily:
linux_env.Command('[output1, output2]', 'data/data_files','compiler_compiler.exe data_files output1 output2')
my problem is number 2: How do I make the script runner depend on outputs of another target
And just to clarify it, I need to make SCONS run (and only if compiler_output changes):
src_dir/script/legacy_script obj_dir/data/compiler_output obj_dir/some_dir/script_output
(the script is usage is: legacy_script input_file output_file)
I hope I made myself clear, feel free to ask some more questions...
I've had a similar problem recently when I needed to compile Cheetah Templates first, which were then used from another Builder to generate HTML files from different sources.
If you define the build output of the first builder as source for the second builder, SCons will run them in the correct order and only if intermediate files have changed.
Wolfgang