[PATCH 02/10] Improve performance of sincosf

[Szabolcs Nagy]

v4:
- Added empty s_sincosf_data.c on targets with their own sincosf.
- Moved round/converttoint changes in math_private.h to separate patch.

This patch is a complete rewrite of sinf, cosf and sincosf.  The new version
is significantly faster, as well as simple and accurate.
The worst-case ULP is 0.56072, maximum relative error is 0.5303p-23 over all
4 billion inputs.  In non-nearest rounding modes the error is 1ULP.

The algorithm uses 3 main cases: small inputs which don't need argument
reduction, small inputs which need a simple range reduction and large inputs
requiring complex range reduction.  The code uses approximate integer
comparisons to quickly decide between these cases - on some targets this may
be slow, so this can be configured to use floating point comparisons.

The small range reducer uses a single reduction step to handle values up to
120.0.  It is fastest on targets which support inlined round instructions.

The large range reducer uses integer arithmetic for simplicity.  It does a
32x96 bit multiply to compute a 64-bit modulo result.  This is more than
accurate enough to handle the worst-case cancellation for values close to
an integer multiple of PI/4.  It could be further optimized, however it is
already much faster than necessary.

sincosf throughput gains on Cortex-A72:
* |x| < 0x1p-12 : 1.6x
* |x| < M_PI_4  : 1.7x
* |x| < 2 * M_PI: 1.5x
* |x| < 120.0   : 1.8x
* |x| < Inf     : 2.3x

On a benchmark with significant use of sincosf the overall speedup is >33%.

ChangeLog:
2018-07-06  Wilco Dijkstra  <wdijkstr@arm.com>
	    Szabolcs Nagy  <szabolcs.nagy@arm.com>

	* math/Makefile: Add s_sincosf_data.c.
	* sysdeps/ia64/fpu/s_sincosf_data.c: New file.
	* sysdeps/ieee754/flt-32/math_config.h (PREFER_FLOAT_COMPARISON): Define.
	* sysdeps/ieee754/flt-32/s_sincosf.h (abstop12): Add new function.
	(sincosf_poly): Likewise.
	(reduce_small): Likewise.
	(reduce_large): Likewise.
	* sysdeps/ieee754/flt-32/s_sincosf.c (sincosf): Rewrite.
	* sysdeps/ieee754/flt-32/s_sincosf_data.c: New file with sincosf data.
	* sysdeps/m68k/m680x0/fpu/s_sincosf_data.c: New file.
	* sysdeps/x86_64/fpu/s_sincosf_data.c: New file.
---
  math/Makefile                            |   2 +-
  sysdeps/ia64/fpu/s_sincosf_data.c        |   1 +
  sysdeps/ieee754/flt-32/math_config.h     |   3 +
  sysdeps/ieee754/flt-32/s_sincosf.c       | 197 ++++++++++---------------------
  sysdeps/ieee754/flt-32/s_sincosf.h       | 119 +++++++++++++++++++
  sysdeps/ieee754/flt-32/s_sincosf_data.c  |  74 ++++++++++++
  sysdeps/m68k/m680x0/fpu/s_sincosf_data.c |   1 +
  sysdeps/x86_64/fpu/s_sincosf_data.c      |   1 +
  8 files changed, 265 insertions(+), 133 deletions(-)
  create mode 100644 sysdeps/ia64/fpu/s_sincosf_data.c
  create mode 100644 sysdeps/ieee754/flt-32/s_sincosf_data.c
  create mode 100644 sysdeps/m68k/m680x0/fpu/s_sincosf_data.c
  create mode 100644 sysdeps/x86_64/fpu/s_sincosf_data.c

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