How to Cross-Compile from LLVM IR to Assembly for ARM Cortex M4?

Question

I'm trying to cross-compile an llvm-ir file to assembly, or better generate an object file, for an ARM Cortex M4 microprocessor using llc compiler.
Which are the parameters that I have to specify in order to do so? I have tried with this command
llc -mtriple=armv7m-eabi -mcpu=cortex-m4 file.ll -o file.s
It doesn't throw any error but the assembly code generated is still for an x86 machine.

In particular, trying to compiling with random parameters, e.g.
llc -mtriple=randomwords -mcpu=cortex-m4 file.ll -o file.s
It goes smooth, producing an assembly code for the x86 machine. It ignores what I specify.

Answer 1

I found a solution, or better a work around to this problem.
Instead of using directly llc, first I've obtained the binary code through this command
llvm-as file.ll -o file.bc
An than I used clang to crosscompile and obtain the object file for ARM Cortex M4 using this instruction
clang --target=arm-none-eabi -march=armv7e-m -mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mfloat-abi=hard -mthumb -nostdlib file.bc -c -o file.o
The -c is used to compile only.
It is also possible to obtain the assembly code by using the following command line
clang -S --target=arm-none-eabi -march=armv7e-m -mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mfloat-abi=hard -mthumb -nostdlib file.bc -o file.s

Answer 2

llc (not sure about prior to v9) seems to only care about the architecture. I can cross compile and link with the following script (for a RPI running Linux):

#/bin/sh
llc-9 -march=arm -float-abi=hard -O3 -filetype obj $1.ll -o $1.o
~/devel/musl/musl-cross-make/output/bin/arm-linux-musleabihf-gcc -mfloat-abi=hard -static $1.o -o $1

llc --version will show the available architectures

Try the following for your case (or use a more specific architecture if it is in the list):

llc -march=arm -mcpu=cortex-m4 -filetype obj file.ll -o file.o