[llvm-dev] *** GMX Spamverdacht *** Re: clang 4.0.0: Invalid code for builtin floating point function with -mfloat-abi=hard -ffast-math (ARM)

[Friedman, Eli via llvm-dev]

Did anything ever happen here?  This still appears to be broken on trunk.

-Eli

On 3/30/2017 4:12 PM, Peter Jakubek wrote:
> I think the problem is here:
>
> llvm\lib\Target\ARM\ARMISelLowering.cpp, line 187:
>
>   if (!Subtarget->isTargetDarwin() && !Subtarget->isTargetIOS() &&
>       !Subtarget->isTargetWatchOS()) {
>     const auto &E = Subtarget->getTargetTriple().getEnvironment();
>
>     bool IsHFTarget = E == Triple::EABIHF || E == Triple::GNUEABIHF ||
>                       E == Triple::MuslEABIHF;
>     // Windows is a special case.  Technically, we will replace all of 
> the "GNU"
>     // calls with calls to MSVCRT if appropriate and adjust the calling
>     // convention then.
>     IsHFTarget = IsHFTarget || Subtarget->isTargetWindows();
>
>     for (int LCID = 0; LCID < RTLIB::UNKNOWN_LIBCALL; ++LCID)
> setLibcallCallingConv(static_cast<RTLIB::Libcall>(LCID),
>                             IsHFTarget ? CallingConv::ARM_AAPCS_VFP
>                                        : CallingConv::ARM_AAPCS);
>   }
>
> IsHFTarget is only true if the target is eabihf. -msoft-abi is 
> completely ignored.
>
> cheers,
>
> Peter
>
> Am 30.03.2017 um 00:15 schrieb Renato Golin:
>> On 29 March 2017 at 02:33, Saleem Abdulrasool <compnerd at compnerd.org> 
>> wrote:
>>> sin/cos are libm functions, and so a libcall to those need to honour 
>>> the
>>> floating point ABI requests.  The calling convention to be followed 
>>> there
>>> should match `-mfloat-abi` (that is, -mfloat-abi=hard => AAPCS/VFP,
>>> -mfloat-abi=soft => AAPCS).
>>
>> Exactly, but they're not, and that's the problem. Do you have any idea
>> why -ffast-math would change their PCS for libc calls?
>>
>> The behaviour seems to have been by your patch
>> (https://reviews.llvm.org/rL291909), so maybe there's some
>> transformation that uses the run-time functions, or some other badly
>> coupled logic...
>>
>> cheers,
>> --renato
>>

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