Does ARM platform have a universal tool chain / compiler?

Question

Recently I tried to make my own cross-compile toolchain for a arm platform. I noticed with the autoconf script of GCC, I have to pass variables like:

--with-cpu=cortex-m4 \
--with-fpu=fpv4-sp-d16 \
--with-float=hard \
--with-mode=thumb \

So it seems different ARM platforms should have different tool chain/compiler cause I have to configure the cpu, fpu etc. But then I found there's some sort of pre-made binaries of these tool chain.

https://developer.arm.com/open-source/gnu-toolchain/gnu-rm/downloads

I tried this tool chain and compiled a hello world program and tried it on my target ARM board, then it shows "segmentation fault." OK, at least it's not "cannot execute binary file: Exec format error"

But I am still wondering, how come it does not work? Or is it suppose to work actually?

Answer 1

When building the toolchain itself, you have to configure which features to support. You can build a "slim" compiler, supporting just the features you need for the target you want.

But you can also support everything the ARM platform has to offer and get a clumsy compiler.

For the features themselves, you should differ between different types:

• Optimization flags like -mcpu are not required, they are only to optimize the code for a certain ARM processor
• The fpu feature of your ARM core on the other hand has to be available to use the fpu at all.
• Your float=hard depends on the operating system, not on the processor: it allows to pass floats to functions in floating registers which can be a big speedup because transfer between ARM registers and float registers are slow. But for linkage, the system needs to agree on that.
• Support for thumb is somehow optional, too. You can use either if the core supports it, but nowadays it would be stupid not to let the compiler choose thumb mode.