Re: [PATCH 00/72] Convert floatx80 and float128 to FloatParts

["Alex Bennée" <alex.bennee@linaro.org>]

Richard Henderson <richard.henderson@linaro.org> writes:

> Reorg everything using QEMU_GENERIC and multiple inclusion to
> reduce the amount of code duplication between the formats.
>
> The use of QEMU_GENERIC means that we need to use pointers instead
> of structures, which means that even the smaller float formats
> need rearranging.

I did a basic some basic benchmarks which show no issues (although I
suspect hardfloat is hiding any true cost of the softfloat itself):

#+name: run-float-benchmarks
#+begin_src shell :results output :async
  ./fp-bench add -p single
  ./fp-bench add -p double
  ./fp-bench mul -p single
  ./fp-bench mul -p double
  ./fp-bench muladd -p single
  ./fp-bench muladd -p double
#+end_src

#+RESULTS: run-float-benchmarks-after
: 374.77 MFlops
: 287.58 MFlops
: 371.55 MFlops
: 281.48 MFlops
: 370.76 MFlops
: 287.39 MFlops

#+RESULTS: run-float-benchmarks-before
: 362.40 MFlops
: 278.65 MFlops
: 360.68 MFlops
: 280.92 MFlops
: 360.75 MFlops
: 280.76 MFlops

I guess what would be really telling is if a ext80 benchmark exhibited
any slowdown.

>
> I've carried it through to completion within fpu/, so that we don't
> have (much) of the legacy code remaining.  There is some floatx80
> stuff in target/m68k and target/i386 that's still hanging around.
>
>
> r~
>
>
> Alex Bennée (1):
>   tests/fp: add quad support to the benchmark utility
>
> Richard Henderson (71):
>   qemu/host-utils: Use __builtin_bitreverseN
>   qemu/host-utils: Add wrappers for overflow builtins
>   qemu/host-utils: Add wrappers for carry builtins
>   accel/tcg: Use add/sub overflow routines in tcg-runtime-gvec.c
>   softfloat: Move the binary point to the msb
>   softfloat: Inline float_raise
>   softfloat: Use float_raise in more places
>   softfloat: Tidy a * b + inf return
>   softfloat: Add float_cmask and constants
>   softfloat: Use return_nan in float_to_float
>   softfloat: fix return_nan vs default_nan_mode
>   target/mips: Set set_default_nan_mode with set_snan_bit_is_one
>   softfloat: Do not produce a default_nan from parts_silence_nan
>   softfloat: Rename FloatParts to FloatParts64
>   softfloat: Move type-specific pack/unpack routines
>   softfloat: Use pointers with parts_default_nan
>   softfloat: Use pointers with unpack_raw
>   softfloat: Use pointers with ftype_unpack_raw
>   softfloat: Use pointers with pack_raw
>   softfloat: Use pointers with ftype_pack_raw
>   softfloat: Use pointers with ftype_unpack_canonical
>   softfloat: Use pointers with ftype_round_pack_canonical
>   softfloat: Use pointers with parts_silence_nan
>   softfloat: Rearrange FloatParts64
>   softfloat: Convert float128_silence_nan to parts
>   softfloat: Convert float128_default_nan to parts
>   softfloat: Move return_nan to softfloat-parts.c.inc
>   softfloat: Move pick_nan to softfloat-parts.c.inc
>   softfloat: Move pick_nan_muladd to softfloat-parts.c.inc
>   softfloat: Move sf_canonicalize to softfloat-parts.c.inc
>   softfloat: Move round_canonical to softfloat-parts.c.inc
>   softfloat: Use uadd64_carry, usub64_borrow in softfloat-macros.h
>   softfloat: Move addsub_floats to softfloat-parts.c.inc
>   softfloat: Implement float128_add/sub via parts
>   softfloat: Move mul_floats to softfloat-parts.c.inc
>   softfloat: Move muladd_floats to softfloat-parts.c.inc
>   softfloat: Use mulu64 for mul64To128
>   softfloat: Use add192 in mul128To256
>   softfloat: Tidy mul128By64To192
>   softfloat: Introduce sh[lr]_double primitives
>   softfloat: Move div_floats to softfloat-parts.c.inc
>   softfloat: Split float_to_float
>   softfloat: Convert float-to-float conversions with float128
>   softfloat: Move round_to_int to softfloat-parts.c.inc
>   softfloat: Move rount_to_int_and_pack to softfloat-parts.c.inc
>   softfloat: Move rount_to_uint_and_pack to softfloat-parts.c.inc
>   softfloat: Move int_to_float to softfloat-parts.c.inc
>   softfloat: Move uint_to_float to softfloat-parts.c.inc
>   softfloat: Move minmax_flags to softfloat-parts.c.inc
>   softfloat: Move compare_floats to softfloat-parts.c.inc
>   softfloat: Move scalbn_decomposed to softfloat-parts.c.inc
>   softfloat: Move sqrt_float to softfloat-parts.c.inc
>   softfloat: Split out parts_uncanon_normal
>   softfloat: Reduce FloatFmt
>   softfloat: Introduce Floatx80RoundPrec
>   softfloat: Adjust parts_uncanon_normal for floatx80
>   tests/fp/fp-test: Reverse order of floatx80 precision tests
>   softfloat: Convert floatx80_add/sub to FloatParts
>   softfloat: Convert floatx80_mul to FloatParts
>   softfloat: Convert floatx80_div to FloatParts
>   softfloat: Convert floatx80_sqrt to FloatParts
>   softfloat: Convert floatx80_round to FloatParts
>   softfloat: Convert floatx80_round_to_int to FloatParts
>   softfloat: Convert integer to floatx80 to FloatParts
>   softfloat: Convert floatx80 float conversions to FloatParts
>   softfloat: Convert floatx80 to integer to FloatParts
>   softfloat: Convert floatx80_scalbn to FloatParts
>   softfloat: Convert floatx80 compare to FloatParts
>   softfloat: Convert float32_exp2 to FloatParts
>   softfloat: Move floatN_log2 to softfloat-parts.c.inc
>   softfloat: Convert modrem operations to FloatParts
>
>  include/fpu/softfloat-helpers.h  |    5 +-
>  include/fpu/softfloat-macros.h   |  247 +-
>  include/fpu/softfloat-types.h    |   10 +-
>  include/fpu/softfloat.h          |   11 +-
>  include/qemu/host-utils.h        |  291 ++
>  target/mips/fpu_helper.h         |   10 +-
>  accel/tcg/tcg-runtime-gvec.c     |   36 +-
>  fpu/softfloat.c                  | 7760 ++++++++++--------------------
>  linux-user/arm/nwfpe/fpa11.c     |   41 +-
>  target/i386/tcg/fpu_helper.c     |   79 +-
>  target/m68k/fpu_helper.c         |   50 +-
>  target/m68k/softfloat.c          |   90 +-
>  tests/fp/fp-bench.c              |   88 +-
>  tests/fp/fp-test-log2.c          |  118 +
>  tests/fp/fp-test.c               |   11 +-
>  fpu/softfloat-parts-addsub.c.inc |   62 +
>  fpu/softfloat-parts.c.inc        | 1480 ++++++
>  fpu/softfloat-specialize.c.inc   |  424 +-
>  tests/fp/wrap.c.inc              |   12 +
>  tests/fp/meson.build             |   11 +
>  20 files changed, 4886 insertions(+), 5950 deletions(-)
>  create mode 100644 tests/fp/fp-test-log2.c
>  create mode 100644 fpu/softfloat-parts-addsub.c.inc
>  create mode 100644 fpu/softfloat-parts.c.inc


-- 
Alex Bennée