Re: [ARM] Enable FP16 vector arithmetic operations.

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

Hi All,

I'm taking this one over from Matthew, I think it slipped through the cracks before.

Since it still applies cleanly on trunk I'm just pinging it.

Ok for trunk?

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  Also remove outdated comment.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.