On 18/05/16 01:58, Joseph Myers wrote:
 > On Tue, 17 May 2016, Matthew Wahab wrote:
 >
 >> As with the VFP FP16 arithmetic instructions, operations on __fp16
 >> values are done by conversion to single-precision. Any new optimization
 >> supported by the instruction descriptions can only apply to code
 >> generated using intrinsics added in this patch series.
 >
 > As with the scalar instructions, I think it is legitimate in most cases to
 > optimize arithmetic via single precision to work direct on __fp16 values
 > (and this would be natural for vectorization of __fp16 arithmetic).
 >
 >> A number of the instructions are modelled as two variants, one using
 >> UNSPEC and the other using RTL operations, with the model used decided
 >> by the funsafe-math-optimizations flag. This follows the
 >> single-precision instructions and is due to the half-precision
 >> operations having the same conditions and restrictions on their use in
 >> optmizations (when they are enabled).
 >
 > (Of course, these restrictions still apply.)

The F16 support generally follows the F32 implementation and, for F32,
direct arithmetic vector operations are only available when
unsafe-math-optimizations is enabled. I want to check the behaviour of
the F16 operations when unsafe-math is enabled so I'll defer to a follow
up patch the change to use standard names for the vector operations.

There are still some changes from the previous patch:

- Two fma/fmsub patterns *fma<VH:mode>4 and <*fmsub<VH:mode>4 are
   dropped since they just duplicated *fma<VH:mode>4_intrinsic and
   <*fmsub<VH:mode>4_intrinsic.

- Patterns neon_vadd<mode>_unspec and neon_vsub<mode>_unspec are
   dropped, they were redundant.

- <absneg_str><mode>2_fp16 is renamed to <absneg_str><mode>2. This
   implements the abs and neg operations which are always safe to use.

- neon_vsqrte<mode> is renamed to neon_vrsqrte<mode>. This is a
   misspelled intrinsic that wasn't caught in testing because the
   relevant test case is missing. The intrinsic is fixed here and in
   other patches and an advsimd-intrinsics test added later in the
   (updated) series.

- neon_vcvt<sup>_n<mode: The bounds on the scalar were wrong, the
   correct range for f16 is 0-17.

- Test armv8_2-fp16-arith-1.c is updated to expect f16 arithmetic
   instructions rather then f32 and to use the neon command line options.

Tested the series for arm-none-linux-gnueabihf with native bootstrap and
make check and for arm-none-eabi and armeb-none-eabi with make check on
an ARMv8.2-A emulator.

Ok for trunk?
Matthew

2016-07-04  Matthew Wahab  <matthew.wahab@arm.com>

	* config/arm/iterators.md (VCVTHI): New.
	(NEON_VCMP): Add UNSPEC_VCLT and UNSPEC_VCLE.  Fix a long line.
	(NEON_VAGLTE): New.
	(VFM_LANE_AS): New.
	(VH_CVTTO): New.
	(V_reg): Add HF, V4HF and V8HF.  Fix white-space.
	(V_HALF): Add V4HF.  Fix white-space.
	(V_if_elem): Add HF, V4HF and V8HF.  Fix white-space.
	(V_s_elem): Likewise.
	(V_sz_elem): Fix white-space.
	(V_elem_ch): Likewise.
	(VH_elem_ch): New.
	(scalar_mul_constraint): Add V8HF and V4HF.
	(Is_float_mode): Fix white-space.
	(Is_d_reg): Fix white-space.
	(q): Add HF.  Fix white-space.
	(float_sup): New.
	(float_SUP): New.
	(cmp_op_unsp): Add UNSPEC_VCALE and UNSPEC_VCALT.
	(neon_vfm_lane_as): New.
	* config/arm/neon.md (add<mode>3_fp16): New.
	(sub<mode>3_fp16): New.
	(mul<mode>3add<mode>_neon): New.
	(fma<VH:mode>4_intrinsic): New.
	(fmsub<VCVTF:mode>4_intrinsic): Fix white-space.
	(fmsub<VH:mode>4_intrinsic): New.
	(<absneg_str><mode>2): New.
	(neon_v<absneg_str><mode>): New.
	(neon_v<fp16_rnd_str><mode>): New.
	(neon_vrsqrte<mode>): New.
	(neon_vpaddv4hf): New.
	(neon_vadd<mode>): New.
	(neon_vsub<mode>): New.
	(neon_vmulf<mode>): New.
	(neon_vfma<VH:mode>): New.
	(neon_vfms<VH:mode>): New.
	(neon_vc<cmp_op><mode>): New.
	(neon_vc<cmp_op><mode>_fp16insn): New
	(neon_vc<cmp_op_unsp><mode>_fp16insn_unspec): New.
	(neon_vca<cmp_op><mode>): New.
	(neon_vca<cmp_op><mode>_fp16insn): New.
	(neon_vca<cmp_op_unsp><mode>_fp16insn_unspec): New.
	(neon_vc<cmp_op>z<mode>): New.
	(neon_vabd<mode>): New.
	(neon_v<maxmin>f<mode>): New.
	(neon_vp<maxmin>fv4hf: New.
	(neon_<fmaxmin_op><mode>): New.
	(neon_vrecps<mode>): New.
	(neon_vrsqrts<mode>): New.
	(neon_vrecpe<mode>): New (VH variant).
	(neon_vdup_lane<mode>_internal): New.
	(neon_vdup_lane<mode>): New.
	(neon_vcvt<sup><mode>): New (VCVTHI variant).
	(neon_vcvt<sup><mode>): New (VH variant).
	(neon_vcvt<sup>_n<mode>): New (VH variant).
	(neon_vcvt<sup>_n<mode>): New (VCVTHI variant).
	(neon_vcvt<vcvth_op><sup><mode>): New.
	(neon_vmul_lane<mode>): New.
	(neon_vmul_n<mode>): New.
	* config/arm/unspecs.md (UNSPEC_VCALE): New
	(UNSPEC_VCALT): New.
	(UNSPEC_VFMA_LANE): New.
	(UNSPECS_VFMS_LANE): New.

testsuite/
2016-07-04  Matthew Wahab  <matthew.wahab@arm.com>

	* gcc.target/arm/armv8_2-fp16-arith-1.c: Use arm_v8_2a_fp16_neon
	options.  Add tests for float16x4_t and float16x8_t.