LLVM & Clang can't compile for a supported arch

Question

Under Ubuntu 64 bit I got

llc --version
LLVM (http://llvm.org/):
  LLVM version 3.1
  Optimized build with assertions.
  Built Oct 15 2012 (18:15:59).
  Defa         


        

Answer 1

the llvm linker links for the host, which is only one of the targets, it wont link to every target in the list. it will definitely compile for any target. Basically clang goes from C/C++ to bytecode, then llc takes bytecode and makes assembly for the specific target (new experrimental option to take the bytecode straight to object file) then you need to get a cross assembler and a cross linker to take it the final mile (I use gnu binutils). Unfortunately I found that clang to bytecode is not completely generic (I had hoped and expected that it would be), it does in fact change the target independent output based on the target. The example below using the host triple instead of using -march allowed for my examples to build properly on more hosts.

ARMGNU?=arm-none-eabi
LOPS = -Wall -m32 -emit-llvm -ccc-host-triple $(ARMGNU)
OOPS = -std-compile-opts
LLCOPS = -march=thumb -mtriple=$(ARMGNU)

    clang $(LOPS) -c blinker03.c -o blinker03.clang.bc
    opt $(OOPS) blinker03.clang.bc -o blinker03.clang.thumb.opt.bc
    llc $(LLCOPS) blinker03.clang.thumb.opt.bc -o blinker03.clang.thumb.opt.s
    $(ARMGNU)-as blinker03.clang.thumb.opt.s -o blinker03.clang.thumb.opt.o
    $(ARMGNU)-ld -o blinker03.clang.thumb.opt.elf -T memmap vectors.o blinker03.clang.thumb.opt.o

I have not, but before long will experiment with using the llc straight to object (actually I tried it on a simple test but have not used it on anything larger or posted it anywhere).