Re: [PATCH v2 7/8] travis: Add ARM thumb target to tests

[Leif Lindholm]

On Tue, May 14, 2019 at 06:32:06AM -0700, Alexander Graf wrote:
> > But, wait...
> > arm-linux-gnueabi is the softfloat (v5te) toolchain - if we want to
> > test that, fine - but we definitely need to test arm-linux-gnueabihf.
> >
> > First of all, I would expect that this toolchain will not use T32
> > (Thumb-2) instructions by default, so much of the code will end up
> > being compiled as A32 anyway.
> 
> 
> Yeah, that's why we don't need to pass in -marm I guess. But I also
> don't see an explicit hardfloat cross gcc on kernel.org?
> 
>   https://mirrors.kernel.org/pub/tools/crosstool/files/bin/x86_64/8.1.0/

Urgh.
Yeah, so the default output of that toolchain gives
  File Attributes
  Tag_CPU_name: "5T"
  Tag_CPU_arch: v5T
  Tag_ARM_ISA_use: Yes
  Tag_THUMB_ISA_use: Thumb-1

In theory, you should be OK just adding
"-mfloat-abi=hard -march=armv7-a+vfpv3-d16" to CFLAGS, since we're not
using any toolchain-provided libraries:

  Tag_CPU_name: "7-A"
  Tag_CPU_arch: v7
  Tag_CPU_arch_profile: Application
  Tag_ARM_ISA_use: Yes
  Tag_THUMB_ISA_use: Thumb-2
  Tag_FP_arch: VFPv3-D16
  Tag_ABI_PCS_wchar_t: 4
  Tag_ABI_FP_denormal: Needed
  Tag_ABI_FP_exceptions: Needed
  Tag_ABI_FP_number_model: IEEE 754
  Tag_ABI_align_needed: 8-byte
  Tag_ABI_align_preserved: 8-byte, except leaf SP
  Tag_ABI_enum_size: int
  Tag_ABI_VFP_args: VFP registers

/
    Leif