Commit graph

24 commits

Author SHA1 Message Date
Richard Henderson 97152bc427
fpu/softfloat: Introduce parts_is_snan_frac
Backports commit 298b468e4389587ab2e8599dd33eff3fbc698011 from qemu
2018-05-19 22:20:03 -04:00
Richard Henderson ff8fab55a2
fpu/softfloat: Split floatXX_silence_nan from floatXX_maybe_silence_nan
The new function assumes that the input is an SNaN and
does not double-check.

Backports commit d619bb98fdcda24f9ee3b7a53a4d555228dbca52 from qemu
2018-05-19 22:06:33 -04:00
Richard Henderson db3479e242
fpu/softfloat: Merge NO_SIGNALING_NANS definitions
Move the ifdef inside the relevant functions instead of
duplicating the function declarations.

Backports commit bca52234d1c04e0665f67708bcdef6d805d60adb from qemu
2018-05-19 21:59:24 -04:00
Lioncash 1c4c5a9403
softfloat-specialize: Perform comparison pass with qemu
Ensures code and formatting are similar
2018-03-21 13:27:59 -04:00
Laurent Vivier 5fa3a97549
softfloat: use floatx80_infinity in softfloat
Since f3218a8 ("softfloat: add floatx80 constants")
floatx80_infinity is defined but never used.

This patch updates floatx80 functions to use
this definition.

This allows to define a different default Infinity
value on m68k: the m68k FPU defines infinity with
all bits set to zero in the mantissa.

Backports commit 0f605c889ca3fe9744166ad4149d0dff6dacb696 from qemu
2018-03-09 01:34:45 -05:00
Laurent Vivier b42fcb5496
softfloat: export some functions
Move fpu/softfloat-macros.h to include/fpu/

Export floatx80 functions to be used by target floatx80
specific implementations.

Exports:
propagateFloatx80NaN(), extractFloatx80Frac(),
extractFloatx80Exp(), extractFloatx80Sign(),
normalizeFloatx80Subnormal(), packFloatx80(),
roundAndPackFloatx80(), normalizeRoundAndPackFloatx80()

Also exports packFloat32() that will be used to implement
m68k fsinh, fcos, fsin, ftan operations.

Backports commit 88857aca93f6ec8f372fb9c8201394b0e5582034 from qemu
2018-03-09 01:22:00 -05:00
Alex Bennée d92d5c6910
fpu/softfloat: re-factor muladd
We can now add float16_muladd and use the common decompose and
canonicalize functions to have a single implementation for
float16/32/64 muladd functions.

Backports commit d446830a3aac33e7221e361dad3ab1e1892646cb from qemu
2018-03-08 10:55:40 -05:00
Alex Bennée b5fdc7b411
fpu/softfloat: improve comments on ARM NaN propagation
Mention the pseudo-code fragment from which this is based.

Backports commit 13894527f522caab4ec74334191ef29af975e521 from qemu
2018-03-08 10:03:32 -05:00
Laurent Vivier 199c62ea01
softfloat: define 680x0 specific values
Backports commit e5b0cbe8e8744b57faf0c62d023525cd466f5ab8 from qemu
2018-03-03 15:01:16 -05:00
Bharata B Rao 4324d1e97e
softfloat: Fix the default qNAN for target-ppc
Currently float128_default_nan() returns 0xFFFF800000000000 in the
higher double word, but it should return 0x7FFF800000000000 which
is the correct higher double word for default qNAN on PowerPC.

Backports commit 5d51eaea84899d88cb161fab3f089168e3812e9e from qemu
2018-03-02 00:15:36 -05:00
Richard Henderson 5c4f79ac62
target-hppa: Add softfloat specializations
Like the original MIPS, HPPA has the MSB of an SNaN set.
However, it has different rules for silencing an SNaN:
(1) msb is cleared and (2) msb-1 must be set if the fraction
is now zero, and (implementation defined) may be set always.
I haven't checked real hardware but chose the set always
alternative because it's easy and within spec.

Backports commit 005fa38d86257d471ac461c066a5409a9f5ebb02 from qemu
2018-03-01 23:42:09 -05:00
Pranith Kumar 1b19fe260a
softfloat: Fix warn about implicit conversion from int to int8_t
Change the flag type to 'uint8_t' to fix the implicit conversion error.

Backports commit dfd607671037ff46d5b16ade10e10efdf0d260be from qemu
2018-02-25 22:54:39 -05:00
Aleksandar Markovic 3e9325f1e9
softfloat: Handle snan_bit_is_one == 0 in MIPS pickNaNMulAdd()
Only for Mips platform, and only for cases when snan_bit_is_one is 0,
correct the order of argument comparisons in pickNaNMulAdd().

For more info, see [1], page 53, section "3.5.3 NaN Propagation".

[1] "MIPS Architecture for Programmers Volume IV-j:
The MIPS32 SIMD Architecture Module",
Imagination Technologies LTD, Revision 1.12, February 3, 2016

Backports commit c27644f0e9659471e1c9355da5b667960d311937 from qemu
2018-02-24 20:40:11 -05:00
Aleksandar Markovic 33833b6605
softfloat: For Mips only, correct default NaN values
Only for Mips platform, and only for cases when snan_bit_is_one is 0,
correct default NaN values (in their 16-, 32-, and 64-bit flavors).

For more info, see [1], page 84, Table 6.3 "Value Supplied When a New
Quiet NaN Is Created", and [2], page 52, Table 3.7 "Default NaN
Encodings".

[1] "MIPS Architecture For Programmers Volume II-A:
The MIPS64 Instruction Set Reference Manual",
Imagination Technologies LTD, Revision 6.04, November 13, 2015

[2] "MIPS Architecture for Programmers Volume IV-j:
The MIPS32 SIMD Architecture Module",
Imagination Technologies LTD, Revision 1.12, February 3, 2016

Backports commit a7c04d545a97126c9df9d96623747d8613aaf7db from qemu
2018-02-24 20:38:23 -05:00
Aleksandar Markovic 33ee9429b2
softfloat: Clean code format in fpu/softfloat-specialize.h
fpu/softfloat-specialize.h is the most critical file in SoftFloat
library, since it handles numerous differences between platforms in
relation to floating point arithmetics. This patch makes the code
in this file more consistent format-wise, and hopefully easier to
debug and maintain.

Backports commit a59eaea64686c8966b7653303660f8c26f285c77 from qemu
2018-02-24 20:35:05 -05:00
Aleksandar Markovic 6eb4fa54f6
softfloat: Implement run-time-configurable meaning of signaling NaN bit
This patch modifies SoftFloat library so that it can be configured in
run-time in relation to the meaning of signaling NaN bit, while, at the
same time, strictly preserving its behavior on all existing platforms.

Background:

In floating-point calculations, there is a need for denoting undefined or
unrepresentable values. This is achieved by defining certain floating-point
numerical values to be NaNs (which stands for "not a number"). For additional
reasons, virtually all modern floating-point unit implementations use two
kinds of NaNs: quiet and signaling. The binary representations of these two
kinds of NaNs, as a rule, differ only in one bit (that bit is, traditionally,
the first bit of mantissa).

Up to 2008, standards for floating-point did not specify all details about
binary representation of NaNs. More specifically, the meaning of the bit
that is used for distinguishing between signaling and quiet NaNs was not
strictly prescribed. (IEEE 754-2008 was the first floating-point standard
that defined that meaning clearly, see [1], p. 35) As a result, different
platforms took different approaches, and that presented considerable
challenge for multi-platform emulators like QEMU.

Mips platform represents the most complex case among QEMU-supported
platforms regarding signaling NaN bit. Up to the Release 6 of Mips
architecture, "1" in signaling NaN bit denoted signaling NaN, which is
opposite to IEEE 754-2008 standard. From Release 6 on, Mips architecture
adopted IEEE standard prescription, and "0" denotes signaling NaN. On top of
that, Mips architecture for SIMD (also known as MSA, or vector instructions)
also specifies signaling bit in accordance to IEEE standard. MSA unit can be
implemented with both pre-Release 6 and Release 6 main processor units.

QEMU uses SoftFloat library to implement various floating-point-related
instructions on all platforms. The current QEMU implementation allows for
defining meaning of signaling NaN bit during build time, and is implemented
via preprocessor macro called SNAN_BIT_IS_ONE.

On the other hand, the change in this patch enables SoftFloat library to be
configured in run-time. This configuration is meant to occur during CPU
initialization, at the moment when it is definitely known what desired
behavior for particular CPU (or any additional FPUs) is.

The change is implemented so that it is consistent with existing
implementation of similar cases. This means that structure float_status is
used for passing the information about desired signaling NaN bit on each
invocation of SoftFloat functions. The additional field in float_status is
called snan_bit_is_one, which supersedes macro SNAN_BIT_IS_ONE.

IMPORTANT:

This change is not meant to create any change in emulator behavior or
functionality on any platform. It just provides the means for SoftFloat
library to be used in a more flexible way - in other words, it will just
prepare SoftFloat library for usage related to Mips platform and its
specifics regarding signaling bit meaning, which is done in some of
subsequent patches from this series.

Further break down of changes:

1) Added field snan_bit_is_one to the structure float_status, and
correspondent setter function set_snan_bit_is_one().

2) Constants <float16|float32|float64|floatx80|float128>_default_nan
(used both internally and externally) converted to functions
<float16|float32|float64|floatx80|float128>_default_nan(float_status*).
This is necessary since they are dependent on signaling bit meaning.
At the same time, for the sake of code cleanup and simplicity, constants
<floatx80|float128>_default_nan_<low|high> (used only internally within
SoftFloat library) are removed, as not needed.

3) Added a float_status* argument to SoftFloat library functions
XXX_is_quiet_nan(XXX a_), XXX_is_signaling_nan(XXX a_),
XXX_maybe_silence_nan(XXX a_). This argument must be present in
order to enable correct invocation of new version of functions
XXX_default_nan(). (XXX is <float16|float32|float64|floatx80|float128>
here)

4) Updated code for all platforms to reflect changes in SoftFloat library.
This change is twofolds: it includes modifications of SoftFloat library
functions invocations, and an addition of invocation of function
set_snan_bit_is_one() during CPU initialization, with arguments that
are appropriate for each particular platform. It was established that
all platforms zero their main CPU data structures, so snan_bit_is_one(0)
in appropriate places is not added, as it is not needed.

[1] "IEEE Standard for Floating-Point Arithmetic",
IEEE Computer Society, August 29, 2008.

Backports commit af39bc8c49224771ec0d38f1b693ea78e221d7bc from qemu
2018-02-24 20:27:12 -05:00
Peter Maydell 2eaf79bfd3
fpu: Replace int8 typedef with int8_t
Replace the int8 softfloat-specific typedef with int8_t.
This change was made with

find include hw fpu target-* -name '*.[ch]' | xargs sed -i -e 's/\bint8\b/int8_t/g'

together with manual removal of the typedef definition, and
manual undoing of various mis-hits.

Backports commit 8f506c709adb7d3bed4ebefefe9487c156192a64 from qemu
2018-02-19 00:33:01 -05:00
Peter Maydell 997ca2f6ea
softfloat: expand out STATUS macro
Expand out and remove the STATUS macro.

Backports commit a2f2d288b5a06e6c680c387c9980d91363f59c61 from qemu
2018-02-12 13:43:13 -05:00
Peter Maydell 48e9546efc
softfloat: expand out STATUS_VAR
Expand out and remove the STATUS_VAR macro.

Backports commit ff32e16e865c78fb54187723f3fd09650cd9b962 from qemu
2018-02-12 13:36:42 -05:00
Peter Maydell 20f696343b
softfloat: Expand out the STATUS_PARAM macro
Expand out STATUS_PARAM wherever it is used and delete the definition.

Backports commit e5a41ffa870ad096eb2f084447fea5dd00a51b31 from qemu
2018-02-12 13:07:53 -05:00
Peter Maydell 606cff6e81
softfloat: Clarify license status
The code in the softfloat source files is under a mixture of
licenses: the original code and many changes from QEMU contributors
are under the base SoftFloat-2a license; changes from Stefan Weil
and RedHat employees are GPLv2-or-later; changes from Fabrice Bellard
are under the BSD license. Clarify this in the comments at the
top of each affected source file, including a statement about
the assumed licensing for future contributions, so we don't need
to remember to ask patch submitters explicitly to pick a license.

Backports commit 16017c48547960539fcadb1f91d252124f442482 from qemu
2018-02-12 13:00:01 -05:00
Peter Maydell eaf3805f36
softfloat: Revert and reimplement remaining parts of b645bb4885 and 5a6932d51d
Revert the parts of commits b645bb4885 and 5a6932d51d which are still
in the codebase and under a SoftFloat-2b license.

Reimplement support for architectures where the most significant bit
in the mantissa is 1 for a signaling NaN rather than a quiet NaN,
by adding handling for SNAN_BIT_IS_ONE being set to the functions
which test values for NaN-ness.

This includes restoring the bugfixes lost in the reversion where
some of the float*_is_quiet_nan() functions were returning true
for both signaling and quiet NaNs.

[This is a mechanical squashing together of two separate "revert"
and "reimplement" patches.]

Backports commit 332d5849708d11b835e0b36f4e26e8b36bfb3f5a from qemu
2018-02-12 12:57:15 -05:00
Peter Maydell a9079657e8
softfloat: Apply patch corresponding to rebasing to softfloat-2a
This commit applies the changes to master which correspond to
replacing commit 158142c2c2df with a set of changes made by:
* taking the SoftFloat-2a release
* mechanically transforming the block comment style
* reapplying Fabrice's original changes from 158142c2c2df

This commit was created by:
diff -u 158142c2c2df import-sf-2a
patch -p1 --fuzz 10 <../relicense-patch.txt
(where import-sf-2a is the branch resulting from the changes above).

Backports commit a7d1ac78e0f1101df2ff84502029a4b0da6024ae from qemu
2018-02-12 12:49:49 -05:00
Nguyen Anh Quynh 344d016104 import 2015-08-21 15:04:50 +08:00