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From:   Vincent Chen <vincentc@andestech.com>
To:     <green.hu@gmail.com>, <arnd@arndb.de>
CC:     <linux-kernel@vger.kernel.org>, <vincentc@andestech.com>
Subject: [PATCH v4 0/5] nds32 FPU port
Date:   Thu, 22 Nov 2018 11:14:33 +0800
Message-ID: <1542856478-795-1-git-send-email-vincentc@andestech.com>
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

  This patch set contains basic components for supporting the nds32 FPU,
such as exception handlers and context switch for FPU registers. By
default, the lazy FPU scheme is supported and the user can configure it
via CONFIG_LZAY_FPU. In addition, a floating point emulator is required
to handle all arithmetic of denormalized number because it is not supported
by the nds32 FPU.

  As mentioned above, the nds32 FPU does not support denormalized number
This means the denormalized operands and results are not permitted. If an
instruction contains denormalized operands, the nds32 FPU will raise an
denormalized input exception to inform kernel to deal with this
instruction. If the result of the instruction is a denormalized number,
normally nds32 FPU will treat it as an underflow case and round the result
to an appropriate value based on current rounding mode. Obviously, there is
a precision gap for tininess number. To reduce this precision gap, kernel
will enable the underflow trap by default to direct all underflow cases to
the floating pointer emulator. By the floating pointer emulator, the
correct denormalized number can be derived in kernel and return to the user
program. The feature can be configured by
CONFIG_SUPPORT_DENORMAL_ARITHMETIC, and if the precision requirement is not
critical for tininess number, user may disables this feature to keep
performance.

  The implementation of floating point emulator is based on soft-fp
which is located in include/math-emu folder. However, soft-fp is too
outdated to pass the current compiler check. The needed modifications
for soft-fp are included in this patch set

Changes in v4:
 - Fix compilation error

Changes in v3:
 - Kernel with FPU support enabled still can run on a CPU without FPU
 - Rename CONFIG_UNLAZY_FPU to CONFIG_LAYZ_FPU
 - Rename _switch() to _switch_fpu()
 - Store FPU context when kernel suspends
 - Modify the comments in code and patch

Changes in v2:
 - Remove the initilzation for floating pointer register before entering to
   signal handler.

Vincent Chen (5):
  nds32: nds32 FPU port
  nds32: Support FP emulation
  nds32: support denormalized result through FP emulator
  math-emu/op-2.h: Use statement expressions to prevent negative
    constant shift
  math-emu/soft-fp.h: (_FP_ROUND_ZERO) cast 0 to void to fix warning

 arch/nds32/Kconfig                       |    1 +
 arch/nds32/Kconfig.cpu                   |   34 +++
 arch/nds32/Makefile                      |    5 +
 arch/nds32/include/asm/bitfield.h        |   15 ++
 arch/nds32/include/asm/elf.h             |   11 +
 arch/nds32/include/asm/fpu.h             |  126 +++++++++++
 arch/nds32/include/asm/fpuemu.h          |   32 +++
 arch/nds32/include/asm/nds32_fpu_inst.h  |  109 +++++++++
 arch/nds32/include/asm/processor.h       |    7 +
 arch/nds32/include/asm/sfp-machine.h     |  158 +++++++++++++
 arch/nds32/include/asm/syscalls.h        |    1 +
 arch/nds32/include/uapi/asm/auxvec.h     |    7 +
 arch/nds32/include/uapi/asm/sigcontext.h |   14 ++
 arch/nds32/include/uapi/asm/udftrap.h    |   13 +
 arch/nds32/include/uapi/asm/unistd.h     |    2 +
 arch/nds32/kernel/Makefile               |    4 +
 arch/nds32/kernel/ex-entry.S             |   24 ++-
 arch/nds32/kernel/ex-exit.S              |   13 +-
 arch/nds32/kernel/ex-scall.S             |    8 +-
 arch/nds32/kernel/fpu.c                  |  269 ++++++++++++++++++++++
 arch/nds32/kernel/process.c              |   64 +++++-
 arch/nds32/kernel/setup.c                |   12 +-
 arch/nds32/kernel/signal.c               |   62 +++++-
 arch/nds32/kernel/sleep.S                |    4 +-
 arch/nds32/kernel/sys_nds32.c            |   32 +++
 arch/nds32/kernel/traps.c                |   16 ++
 arch/nds32/math-emu/Makefile             |    7 +
 arch/nds32/math-emu/faddd.c              |   24 ++
 arch/nds32/math-emu/fadds.c              |   24 ++
 arch/nds32/math-emu/fcmpd.c              |   24 ++
 arch/nds32/math-emu/fcmps.c              |   24 ++
 arch/nds32/math-emu/fd2s.c               |   22 ++
 arch/nds32/math-emu/fdivd.c              |   27 +++
 arch/nds32/math-emu/fdivs.c              |   26 +++
 arch/nds32/math-emu/fmuld.c              |   23 ++
 arch/nds32/math-emu/fmuls.c              |   23 ++
 arch/nds32/math-emu/fnegd.c              |   21 ++
 arch/nds32/math-emu/fnegs.c              |   21 ++
 arch/nds32/math-emu/fpuemu.c             |  357 ++++++++++++++++++++++++++++++
 arch/nds32/math-emu/fs2d.c               |   23 ++
 arch/nds32/math-emu/fsqrtd.c             |   21 ++
 arch/nds32/math-emu/fsqrts.c             |   21 ++
 arch/nds32/math-emu/fsubd.c              |   27 +++
 arch/nds32/math-emu/fsubs.c              |   27 +++
 include/math-emu/op-2.h                  |   97 ++++-----
 include/math-emu/soft-fp.h               |    2 +-
 46 files changed, 1816 insertions(+), 68 deletions(-)
 create mode 100644 arch/nds32/include/asm/fpu.h
 create mode 100644 arch/nds32/include/asm/fpuemu.h
 create mode 100644 arch/nds32/include/asm/nds32_fpu_inst.h
 create mode 100644 arch/nds32/include/asm/sfp-machine.h
 create mode 100644 arch/nds32/include/uapi/asm/udftrap.h
 create mode 100644 arch/nds32/kernel/fpu.c
 create mode 100644 arch/nds32/math-emu/Makefile
 create mode 100644 arch/nds32/math-emu/faddd.c
 create mode 100644 arch/nds32/math-emu/fadds.c
 create mode 100644 arch/nds32/math-emu/fcmpd.c
 create mode 100644 arch/nds32/math-emu/fcmps.c
 create mode 100644 arch/nds32/math-emu/fd2s.c
 create mode 100644 arch/nds32/math-emu/fdivd.c
 create mode 100644 arch/nds32/math-emu/fdivs.c
 create mode 100644 arch/nds32/math-emu/fmuld.c
 create mode 100644 arch/nds32/math-emu/fmuls.c
 create mode 100644 arch/nds32/math-emu/fnegd.c
 create mode 100644 arch/nds32/math-emu/fnegs.c
 create mode 100644 arch/nds32/math-emu/fpuemu.c
 create mode 100644 arch/nds32/math-emu/fs2d.c
 create mode 100644 arch/nds32/math-emu/fsqrtd.c
 create mode 100644 arch/nds32/math-emu/fsqrts.c
 create mode 100644 arch/nds32/math-emu/fsubd.c
 create mode 100644 arch/nds32/math-emu/fsubs.c