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Re: [Qemu-devel] [PATCH v2 02/16] softloat: disable floatx80_invalid_enc
From: |
Andreas Schwab |
Subject: |
Re: [Qemu-devel] [PATCH v2 02/16] softloat: disable floatx80_invalid_encoding() for m68k |
Date: |
Mon, 30 Jan 2017 23:47:06 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.1.91 (gnu/linux) |
On Jan 30 2017, Peter Maydell <address@hidden> wrote:
> I guess we need to look more carefully at exactly what the
> m68k does for these encodings (maybe have a 'normalize value'
> function which squashes them down to whatever the equivalent
> non-weird encoding is?).
On the m68k, the concept of pseudo-inf/nan doesn't exist, because the
integer bit is don't-care for inf and nan. The combination of a zero
integer bit with other non-zero biased exponents is called unnormal, and
the 68881/2 will always convert them to normal/denormal/zero on input.
(The 68040/60 don't support denormal/unnormal in hardware and lets the
support library handle them, which presumably works the same way as the
68881/2.)
Andreas.
--
Andreas Schwab, address@hidden
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."
- [Qemu-devel] [PATCH v2 00/16] target-m68k: implement 680x0 FPU, Laurent Vivier, 2017/01/30
- [Qemu-devel] [PATCH v2 01/16] softfloat: define 680x0 specific values, Laurent Vivier, 2017/01/30
- [Qemu-devel] [PATCH v2 02/16] softloat: disable floatx80_invalid_encoding() for m68k, Laurent Vivier, 2017/01/30
- [Qemu-devel] [PATCH v2 04/16] target-m68k: define ext_opsize, Laurent Vivier, 2017/01/30
- [Qemu-devel] [PATCH v2 07/16] target-m68k: manage FPU exceptions, Laurent Vivier, 2017/01/30
- [Qemu-devel] [PATCH v2 03/16] target-m68k: move FPU helpers to fpu_helper.c, Laurent Vivier, 2017/01/30
- [Qemu-devel] [PATCH v2 13/16] target-m68k: add fsglmul and fsgldiv, Laurent Vivier, 2017/01/30
- [Qemu-devel] [PATCH v2 08/16] target-m68k: define 96bit FP registers for gdb on 680x0, Laurent Vivier, 2017/01/30
- [Qemu-devel] [PATCH v2 06/16] target-m68k: add FPCR and FPSR, Laurent Vivier, 2017/01/30
- [Qemu-devel] [PATCH v2 10/16] target-m68k: add fscc., Laurent Vivier, 2017/01/30
- [Qemu-devel] [PATCH v2 09/16] target-m68k: add fmovem, Laurent Vivier, 2017/01/30
- [Qemu-devel] [PATCH v2 12/16] target-m68k: add fscale, fgetman, fgetexp and fmod, Laurent Vivier, 2017/01/30
- [Qemu-devel] [PATCH v2 14/16] target-m68k: add explicit single and double precision operations, Laurent Vivier, 2017/01/30