arm - Illegal instruction when running simple ELLCC-generated ELF binary on a Raspberry Pi -


i have empty program in llvm ir:

define i32 @main(i32 %argc, i8** %argv) nounwind { entry:     ret i32 0 }

i'm cross-compiling on intel x86-64 windows arm linux using ellcc, following command:

ecc++ hw.ll -o hw.o -target arm-linux-engeabihf

it completes without errors , generates elf binary.

when take binary raspberry pi model b+ (running raspbian), following error:

illegal instruction

i don't know how tell what's wrong the disassembled code. tried other arm linux targets behavior same. what's wrong?

the exact same file builds, links , runs fine other targets i386-linux-eng, x86_64-w64-mingw32, etc (that test on), again using ellcc toolchain.

assuming library , startup code isn't @ fault, disassembly of main looks like:

.text:00010188  e24dd008    sub sp, sp, #8 .text:0001018c  e3002000    movw r2, #0 .text:00010190  e58d0004    str r0, [sp, #4] .text:00010194  e1a00002    mov r0, r2 .text:00010198  e58d1000    str r1, [sp] .text:0001019c  e28dd008    add sp, sp, #8 .text:000101a0  e12fff1e    bx lr

i'd guess it's choking on movw @ 0x0001018c. movw/movt encodings can handle full 16-bit immediate values first appeared in armv6t2 version of architecture - arm1176 in original pi models predates that, supporting original armv6*.

you need tell compiler generate code appropriate thing you're running on - don't know ellcc, i'd guess it's modern , up-to-date , defaulting newer armv6t2 or armv7. otherwise, it's akin generating code pentium , hoping works on 80486 - might lucky, might not. said, there's no reason should have chosen encoding in first place - it's not if 0 can't encoded in 'classic' mov instruction...

the decadent option, however, consider perfect excuse replace pi pi 2 - cortex-a7s in nice capable armv7 cores ;)

* lies clarity. think 1176 might v6k, that's irrelevant here. i'm not sure if exists plain armv6, , various architecture extensions frankly hideous mess


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