[PATCH] add better support for Raspberry Pi board

[Simon Marlow]

I've finished this now.  I committed the second part of your patch (the 
DriverPipeline one), fixed up the "detection" of hard-float, which was 
based on the triple passed to --target but needed some tweaking, and 
I've made it detect VFPv2 from the C compiler.  We should probably be 
doing the hard-float detection the same way.

So now you don't need any special -optlc options for registerised 
compilation with LLVM on Raspberry Pi, it just works.

Cheers,
	Simon

On 25/01/13 21:23, Karel Gardas wrote:
>
> BTW: I've forgot to mention: hard versus soft float abis are well
> detected by configure itself. So this is not the problem in my patch.
> The only issue is in testing/guessing for FPU/NEON. Good way may be to
> grep /proc/cpuinfo but this is only applicable while doing native
> compile on ARM-Linux platform. Is that what majority of GHC users will
> do? I don't think so as I think the way for majority will be
> cross-compilation but perhaps we can at least try it for those doing
> native compiles? What do you think about it?
>
> Thanks!
> Karel
>
> On 01/25/13 09:59 PM, Karel Gardas wrote:
>> On 01/25/13 09:38 PM, Simon Marlow wrote:
>>> This would improve things for RPi, but we shouldn't be guessing here.
>>> gcc has predefines for the appropriate features:
>>>
>>> #define __ARM_PCS_VFP 1
>>>
>>> indicates hard-float ABI, and
>>>
>>> #define __VFP_FP__ 1
>>>
>>> indicates VFP presences (2 or 3? I don't know)
>>
>> The problem is that IIRC those defines are presented when you use
>> appropriate GCC's command-line option. It does not tell anything about
>> the target hardware itself. So that's why I'm just guessing in the
>> patch. But honestly speaking do you think there is any other GHC user
>> who would use GHC on ARMv6 and the hardware will be different than RPi?
>> I think a chance for this is very low since otherwise everybody is using
>> ARMv7 these days...
>>
>> Anyway, if you don't like guessing, what about to add few configure
>> options which will drive the generation of ARM related bits into
>> settings file and keeping some good defaults like we use now? i.e.
>> ARMv7+VFPv3+NEON or ARMv6+VFPv2 or ARMv5 alone?
>>
>> Thanks!
>> Karel
>>
>>>
>>> Cheers,
>>> Simon
>>>
>>> On 25/01/13 15:56, Karel Gardas wrote:
>>>> This patch adds support for Raspberry Pi board. The board is based
>>>> on Broadcom BCM2835, which includes ARM1176JZF-S CPU core. The core
>>>> is classical ARM11 so implementing ARMv6 ISA, but also provides VFPv2
>>>> FPU
>>>> unit. As this looks like fairly popular hardware, in this patch we
>>>> assume
>>>> detected ARMv6 hardware to support VFPv2. Also as Raspberry Pi is very
>>>> commonly
>>>> used with hard-float ABI Linux distribution, the patch relaxes a
>>>> condition
>>>> of "hard-float support for ARMv7 only" to any general ARM core.
>>>> ---
>>>> aclocal.m4 | 2 +-
>>>> compiler/main/DriverPipeline.hs | 9 ++++++---
>>>> 2 files changed, 7 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/aclocal.m4 b/aclocal.m4
>>>> index edbe389..b23568f 100644
>>>> --- a/aclocal.m4
>>>> +++ b/aclocal.m4
>>>> @@ -369,7 +369,7 @@ AC_DEFUN([GET_ARM_ISA],
>>>> [AC_DEFINE(arm_HOST_ARCH_PRE_ARMv7, 1, [ARM pre v7])
>>>> changequote(, )dnl
>>>> ARM_ISA=ARMv6
>>>> - ARM_ISA_EXT="[]"
>>>> + ARM_ISA_EXT="[VFPv2]"
>>>> changequote([, ])dnl
>>>> ],
>>>> [changequote(, )dnl
>>>> diff --git a/compiler/main/DriverPipeline.hs
>>>> b/compiler/main/DriverPipeline.hs
>>>> index c24bb51..81d0bc0 100644
>>>> --- a/compiler/main/DriverPipeline.hs
>>>> +++ b/compiler/main/DriverPipeline.hs
>>>> @@ -1454,14 +1454,17 @@ runPhase LlvmLlc input_fn dflags
>>>> else if (elem VFPv3D16 ext)
>>>> then ["-mattr=+v7,+vfp3,+d16"]
>>>> else []
>>>> + ArchARM ARMv6 ext _ -> if (elem VFPv2 ext)
>>>> + then ["-mattr=+v6,+vfp2"]
>>>> + else ["-mattr=+v6"]
>>>> _ -> []
>>>> -- On Ubuntu/Debian with ARM hard float ABI, LLVM's llc still
>>>> -- compiles into soft-float ABI. We need to explicitly set abi
>>>> -- to hard
>>>> abiOpts = case platformArch (targetPlatform dflags) of
>>>> - ArchARM ARMv7 _ HARD -> ["-float-abi=hard"]
>>>> - ArchARM ARMv7 _ _ -> []
>>>> - _ -> []
>>>> + ArchARM _ _ HARD -> ["-float-abi=hard"]
>>>> + ArchARM _ _ _ -> []
>>>> + _ -> []
>>>>
>>>> sseOpts | isSse4_2Enabled dflags = ["-mattr=+sse42"]
>>>> | isSse2Enabled dflags = ["-mattr=+sse2"]
>>>>
>>>
>>>
>>
>>
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>