RE: [ARM] Enable FP16 vector arithmetic operations.

[Tamar Christina <Tamar.Christina@arm.com>]

Hi Kyrill,
> 
> Sorry for missing this.
> For the record you are referring to the patch at:
> https://gcc.gnu.org/ml/gcc-patches/2016-09/msg01700.html
> 
> This is ok and in line with what we do for the f32 intrinsics.
> My only concern was that we can do this only if
> __ARM_FEATURE_FP16_VECTOR_ARITHMETIC
> is defined from the architecture/fpu level, but these intrinsics are already
> gated on that in arm_neon.h.
> 
> This is ok for trunk if a bootstrap and test run on arm-none-linux-gnueabihf
> with current trunk shows no issues.

Thanks, bootstrapped and regtested now on arm-none-linux-gnueabihf and no issues.
I'll go ahead and commit then.

Regards,
Tamar

> 
> Thanks,
> Kyrill
> 
> > Tamar
> > ________________________________________
> > From: gcc-patches-owner@gcc.gnu.org <gcc-patches-owner@gcc.gnu.org>
> on
> > behalf of Matthew Wahab <matthew.wahab@foss.arm.com>
> > Sent: Friday, September 23, 2016 4:02 PM
> > To: gcc-patches
> > Subject: [ARM] Enable FP16 vector arithmetic operations.
> >
> > Hello,
> >
> > Support for the ARMv8.2-A FP16 NEON arithmetic instructions was added
> > using non-standard names for the instruction patterns. This was needed
> > because the NEON floating point semantics meant that their use by the
> > compiler for HFmode arithmetic operations needed to be restricted.
> > This follows the implementation for 32-bit NEON intructions.
> >
> > As with the 32-bit instructions, the restriction on the HFmode
> > operation can be lifted when -funsafe-math-optimizations is enabled.
> > This patch does that, defining the standard pattern names addhf3,
> > subhf3, mulhf3 and fmahf3.
> >
> > This patch also updates the NEON intrinsics to use the arithmetic
> > operations when -ffast-math is enabled. This is to make keep the
> > 16-bit support consistent with the 32-bit supportd. It is needed so
> > that code using the f16 intrinsics are subject to the same
> > optimizations as code using the f32 intrinsics would be.
> >
> > Tested for arm-none-linux-gnueabihf with native bootstrap and make
> > check on ARMv8-A and for arm-none-eabi and armeb-none-eabi with
> > cross-compiled make check on an ARMv8.2-A emulator.
> >
> > Ok for trunk?
> > Matthew
> >
> > gcc/
> > 2016-09-23  Matthew Wahab  <matthew.wahab@arm.com>
> >
> >         * config/arm/arm_neon.h (vadd_f16): Use standard arithmetic
> >         operations in fast-math mode.
> >         (vaddq_f16): Likewise.
> >         (vmul_f16): Likewise.
> >         (vmulq_f16): Likewise.
> >         (vsub_f16): Likewise.
> >         (vsubq_f16): Likewise.
> >         * config/arm/neon.md (add<mode>3): New.
> >         (sub<mode>3): New.
> >         (fma:<VH:mode>3): New.  Also remove outdated comment.
> >         (mul<mode>3): New.
> >
> > testsuite/
> > 2016-09-23  Matthew Wahab  <matthew.wahab@arm.com>
> >
> >         * gcc.target/arm/armv8_2-fp16-arith-1.c: Expand comment.  Update
> >         expected output of vadd, vsub and vmul instructions.
> >         * gcc.target/arm/armv8_2-fp16-arith-2.c: New.
> >         * gcc.target/arm/armv8_2-fp16-neon-2.c: New.
> >         * gcc.target/arm/armv8_2-fp16-neon-3.c: New.