[PATCH][ARM] Optimize copysign/copysignf for soft-float using BFI

[Jiong Wang]

On 01/12/14 15:33, Christophe Lyon wrote:
> On 27 November 2014 at 11:35, Ramana Radhakrishnan
> <ramana.gcc@googlemail.com> wrote:
>> On Wed, Oct 29, 2014 at 10:20 AM, Jiong Wang <jiong.wang@arm.com> wrote:
>>> On 26/08/14 13:36, Richard Earnshaw wrote:
>>>
>>>> On 29/07/14 15:49, Jiong Wang wrote:
>>>>> test done
>>>>> ===
>>>>> no regression on the full toolchain test on arm-none-eabi.
>>>>>
>>>>>
>>>>> ok to install?
>>>> Hmm, I think this is wrong for DF mode.  The principle the patch works
>>>> on is by tying the output to the value containing the sign bit, and then
>>>> copying the rest of the other value into that value.  However, for DF
>>>> mode it only copies 31 of the 63 bits needed; the least significant 32
>>>> bits of the mantissa are not copied over.
>>>>
>>>> R.
>>>
>>> updated the patch. fixed the DF mode bug.
>>>
>>> no regression on arm-none-eabi multi-lib test.
>>>
>>> ok to trunk?
>>>
>>> gcc/
>>>    * config/arm/arm.md (copysignsf3): New define_expand for SImode.
>> New pattern.
>>
>>>    (copysigndf3): New define_expand for DImode.
>> Likewise.
>>
>> Ok for trunk if no regressions.
> I can see the new test fail at link time, when GCC is configured to
> default to 'hf' (e.g. --target arm-none-linux-gnueabihf), because the
> dg-skip-if directive is not accurate enough.

painful with these multi-lib test...
haven't found a way in dejagnu to 100% make sure the options to override all others ...
especially when pre configure, local board file, testcase dg-options, various things mixed
together...

> Additionally, you require arm_thumb2_ok, but do not force -mthumb in
> dg-options. Do you really need it?

I could recall, the arm_thumb2_ok there serve as arch level check to make sure bfi insn available.
if you remove it, then the case will run even if there is no BFI, but then it's testing copysign builtin
not the optimized pattern we added.

>
>> Sorry about the slow review.
>>
>> Ramana
>>
>>
>>> gcc/testsuite/
>>>    * gcc.target/arm/copysign_softfloat_1.c: New copysign/copysignf testcase
>>> for soft-float.