The right option combination to compile into ARM/Thumb2 code.

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1

Hello,

I'm trying to convince llc to compile into thumb2 ISA on ARMv7. I'm using:

-march=thumb -mattr=v7,thumb2,vfp3

but llc complains about this with:

llc: error: invalid target 'thumb -mattr=v7,thumb2,vfp3'

I'm using LLVM from Aug 29 2011. To me the set of options looks sane so I'd like to ask what's wrong with this.

Thanks!
Karel

2

Hi Karel,

It actually looks like the argument parser has parsed "thumb -mattr=v7,thumb2,vfp3" as the full argument to "-march=". Strange.

The easiest way to get what you want is probably "-mtriple thumbv7--". v7 has Thumb2 enabled and VFPv3 (along with NEON) by default.

Cheers,

James

3

Hi James,

Hi Karel,

It actually looks like the argument parser has parsed "thumb -mattr=v7,thumb2,vfp3" as the full argument to "-march=". Strange.

thanks a lot for this remark. It actually solved my issue. It was caused by me telling GHC to pass all those params by using one -optlc parameter but this indeed results in llc receiving whole this string as one parameter. So instead of wrong:

-optlc="-march=thumb -mattr=v7,thumb2,vfp3"

I need to use:

-optlc=-march=thumb -optlc=-mattr=v7,thumb2,vfp3

where -optlc passes its argument to llc command.

Thanks!
Karel