Commit Graph

140 Commits

Author SHA1 Message Date
Richard Henderson
2f6c74be59 softfloat: Add scaling float-to-int routines
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20180814002653.12828-3-richard.henderson@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2018-08-24 13:17:30 +01:00
Richard Henderson
2abdfe2440 softfloat: Add scaling int-to-float routines
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20180814002653.12828-2-richard.henderson@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2018-08-24 13:17:29 +01:00
Richard Henderson
64d450a0ea softfloat: Fix missing inexact for floating-point add
For 0x1.0000000000003p+0 + 0x1.ffffffep+14 = 0x1.0001fffp+15
we dropped the sticky bit and so failed to raise inexact.

Reported-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Tested-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Message-id: 20180810193129.1556-7-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2018-08-16 14:29:58 +01:00
Richard Henderson
377ed92679 fpu/softfloat: Define floatN_silence_nan in terms of parts_silence_nan
Isolate the target-specific choice to 3 functions instead of 6.

The code in floatx80_default_nan tried to be over-general.  There are
only two targets that support this format: x86 and m68k.  Thus there
is no point in inventing a mechanism for snan_bit_is_one.

Move routines that no longer have ifdefs out of softfloat-specialize.h.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-05-17 15:27:15 -07:00
Richard Henderson
0218a16e54 fpu/softfloat: Define floatN_default_nan in terms of parts_default_nan
Isolate the target-specific choice to 2 functions instead of 6.

The code in float16_default_nan was only correct for ARM, MIPS, and X86.
Though float16 support is rare among our targets.

The code in float128_default_nan was arguably wrong for Sparc.  While
QEMU supports the Sparc 128-bit insns, no real cpu enables it.

The code in floatx80_default_nan tried to be over-general.  There are
only two targets that support this format: x86 and m68k.  Thus there
is no point in inventing a value for snan_bit_is_one.

Move routines that no longer have ifdefs out of softfloat-specialize.h.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-05-17 15:27:15 -07:00
Richard Henderson
3bd2dec1a1 fpu/softfloat: Pass FloatClass to pickNaNMulAdd
For each operand, pass a single enumeration instead of a pair of booleans.
The commit also merges multiple different ifdef-selected implementations
of pickNaNMulAdd into a single function whose body is ifdef-selected.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-05-17 15:27:15 -07:00
Richard Henderson
4f251cfd52 fpu/softfloat: Pass FloatClass to pickNaN
For each operand, pass a single enumeration instead of a pair of booleans.
The commit also merges multiple different ifdef-selected implementations
of pickNaN into a single function whose body is ifdef-selected.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-05-17 15:27:15 -07:00
Richard Henderson
247d1f2190 fpu/softfloat: Make is_nan et al available to softfloat-specialize.h
We will need these helpers within softfloat-specialize.h, so move
the definitions above the include.  After specialization, they will
not always be used so mark them to avoid the Werror.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-05-17 15:27:15 -07:00
Alex Bennée
6fed16b265 fpu/softfloat: re-factor float to float conversions
This allows us to delete a lot of additional boilerplate
code which is no longer needed.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-05-17 15:27:15 -07:00
Alex Bennée
ca3a3d5a31 fpu/softfloat: Partial support for ARM Alternative half-precision
For float16 ARM supports an alternative half-precision format which
sacrifices the ability to represent NaN/Inf in return for a higher
dynamic range.  The new FloatFmt flag, arm_althp, is then used to
modify the behaviour of canonicalize and round_canonical with respect
to representation and exception raising.

Usage of this new flag waits until we re-factor float-to-float conversions.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-05-17 15:27:15 -07:00
Richard Henderson
0bcfbcbea5 fpu/softfloat: Replace float_class_msnan with parts_silence_nan
With a canonical representation of NaNs, we can silence an SNaN
immediately rather than delay until the final format is known.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-05-17 15:24:19 -07:00
Richard Henderson
f7e598e264 fpu/softfloat: Replace float_class_dnan with parts_default_nan
With a canonical representation of NaNs, we can return the
default nan directly rather than delay the expansion until
the final format is known.

Note one case where we uselessly assigned to a.sign, which was
overwritten/ignored later when expanding float_class_dnan.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-05-17 15:24:19 -07:00
Richard Henderson
298b468e43 fpu/softfloat: Introduce parts_is_snan_frac
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-05-17 15:24:19 -07:00
Richard Henderson
94933df0e5 fpu/softfloat: Canonicalize NaN fraction
Shift the NaN fraction to a canonical position, much like we
do for the fraction of normal numbers.  This will facilitate
manipulation of NaNs within the shared code paths.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-05-17 15:24:19 -07:00
Richard Henderson
0664335a6e fpu/softfloat: Move softfloat-specialize.h below FloatParts definition
We want to be able to specialize on the canonical representation.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-05-17 15:24:19 -07:00
Petr Tesarik
6603d50648 fpu/softfloat: Fix conversion from uint64 to float128
The significand is passed to normalizeRoundAndPackFloat128() as high
first, low second. The current code passes the integer first, so the
result is incorrectly shifted left by 64 bits.

This bug affects the emulation of s390x instruction CXLGBR (convert
from logical 64-bit binary-integer operand to extended BFP result).

Cc: qemu-stable@nongnu.org
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Petr Tesarik <ptesarik@suse.com>
Message-Id: <20180511071052.1443-1-ptesarik@suse.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-05-17 15:24:19 -07:00
Peter Maydell
333583757c fpu/softfloat: Don't set Invalid for float-to-int(MAXINT)
In float-to-integer conversion, if the floating point input
converts exactly to the largest or smallest integer that
fits in to the result type, this is not an overflow.
In this situation we were producing the correct result value,
but were incorrectly setting the Invalid flag.
For example for Arm A64, "FCVTAS w0, d0" on an input of
0x41dfffffffc00000 should produce 0x7fffffff and set no flags.

Fix the boundary case to take the right half of the if()
statements.

This fixes a regression from 2.11 introduced by the softfloat
refactoring.

Cc: qemu-stable@nongnu.org
Fixes: ab52f973a5
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20180510140141.12120-1-peter.maydell@linaro.org
2018-05-15 14:58:42 +01:00
Alex Bennée
a5a5f5e2e4 fpu/softfloat: int_to_float ensure r fully initialised
Reported by Coverity (CID1390635). We ensure this for uint_to_float
later on so we might as well mirror that.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2018-05-15 14:58:42 +01:00
Peter Maydell
1839189bbf softfloat: Handle default NaN mode after pickNaNMulAdd, not before
It is implementation defined whether a multiply-add of
(0,inf,qnan) or (inf,0,qnan) raises InvalidaOperation or
not, so we let the target-specific pickNaNMulAdd function
handle this. This means that we must do the "return the
default NaN in default NaN mode" check after the call,
not before. Correct the ordering, and restore the comment
from the old propagateFloat64MulAddNaN() that warned about
this corner case.

This fixes a regression from 2.11 for Arm guests where we would
incorrectly fail to set the Invalid flag for these cases.

Cc: qemu-stable@nongnu.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 20180504100547.14621-1-peter.maydell@linaro.org
2018-05-10 18:10:56 +01:00
Richard Henderson
ce8d408205 fpu: Bound increment for scalbn
Without bounding the increment, we can overflow exp either here
in scalbn_decomposed or when adding the bias in round_canonical.
This can result in e.g. underflowing to 0 instead of overflowing
to infinity.

The old softfloat code did bound the increment.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2018-04-17 14:52:38 +01:00
Alex Bennée
9cb4e398c2 fpu/softfloat: check for Inf / x or 0 / x before /0
The re-factoring of div_floats changed the order of checking meaning
an operation like -inf/0 erroneously raises the divbyzero flag.
IEEE-754 (2008) specifies this should only occur for operations on
finite operands.

We fix this by moving the check on the dividend being Inf/0 to before
the divisor is zero check.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 20180416135442.30606-1-alex.bennee@linaro.org
Cc: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Reviewed-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Tested-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2018-04-16 18:40:48 +01:00
Alex Bennée
801bc56336 fpu/softfloat: raise float_invalid for NaN/Inf in round_to_int_and_pack
The re-factor broke the raising of INVALID when NaN/Inf is passed to
the float_to_int conversion functions. round_to_uint_and_pack got this
right for NaN but also missed out the Inf handling.

Fixes https://bugs.launchpad.net/qemu/+bug/1759264

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Tested-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20180413140334.26622-3-alex.bennee@linaro.org
Cc: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2018-04-16 10:10:31 +01:00
Emilio G. Cota
6245327a36 softfloat: fix {min, max}nummag for same-abs-value inputs
Before 8936006 ("fpu/softfloat: re-factor minmax", 2018-02-21),
we used to return +Zero for maxnummag(-Zero,+Zero); after that
commit, we return -Zero.

Fix it by making {min,max}nummag consistent with {min,max}num,
deferring to the latter when the absolute value of the operands
is the same.

With this fix we now pass fp-test.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 20180413140334.26622-2-alex.bennee@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2018-04-13 15:47:53 +01:00
Richard Henderson
bd49e6027c fpu: Fix rounding mode for floatN_to_uintM_round_to_zero
We incorrectly passed in the current rounding mode
instead of float_round_to_zero.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20180410055912.934-1-richard.henderson@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2018-04-10 13:02:26 +01:00
Stef O'Rear
cffad426f5 softfloat: fix crash on int conversion of SNaN
Signed-off-by: Stef O'Rear <sorear2@gmail.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2018-03-09 14:30:12 +00:00
Laurent Vivier
0f605c889c 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.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20180224201802.911-4-laurent@vivier.eu>
2018-03-04 17:27:35 +01:00
Laurent Vivier
88857aca93 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.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20180224201802.911-2-laurent@vivier.eu>
2018-03-04 17:22:55 +01:00
Alex Bennée
c13bb2da9e fpu/softfloat: re-factor sqrt
This is a little bit of a departure from softfloat's original approach
as we skip the estimate step in favour of a straight iteration. There
is a minor optimisation to avoid calculating more bits of precision
than we need however this still brings a performance drop, especially
for float64 operations.

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
2018-02-21 10:21:54 +00:00
Alex Bennée
0c4c909291 fpu/softfloat: re-factor compare
The compare function was already expanded from a macro. I keep the
macro expansion but move most of the logic into a compare_decomposed.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
2018-02-21 10:21:47 +00:00
Alex Bennée
8936006707 fpu/softfloat: re-factor minmax
Let's do the same re-factor treatment for minmax functions. I still
use the MACRO trick to expand but now all the checking code is common.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
2018-02-21 10:21:41 +00:00
Alex Bennée
0bfc9f1952 fpu/softfloat: re-factor scalbn
This is one of the simpler manipulations you could make to a floating
point number.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
2018-02-21 10:21:34 +00:00
Alex Bennée
c02e1fb80b fpu/softfloat: re-factor int/uint to float
These are considerably simpler as the lower order integers can just
use the higher order conversion function. As the decomposed fractional
part is a full 64 bit rounding and inexact handling comes from the
pack functions.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
2018-02-21 10:21:29 +00:00
Alex Bennée
ab52f973a5 fpu/softfloat: re-factor float to int/uint
We share the common int64/uint64_pack_decomposed function across all
the helpers and simply limit the final result depending on the final
size.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
2018-02-21 10:21:22 +00:00
Alex Bennée
dbe4d53a59 fpu/softfloat: re-factor round_to_int
We can now add float16_round_to_int and use the common round_decomposed and
canonicalize functions to have a single implementation for
float16/32/64 round_to_int functions.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
2018-02-21 10:21:16 +00:00
Alex Bennée
d446830a3a 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.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
2018-02-21 10:21:11 +00:00
Alex Bennée
cf07323d49 fpu/softfloat: re-factor div
We can now add float16_div and use the common decompose and
canonicalize functions to have a single implementation for
float16/32/64 versions.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
2018-02-21 10:21:06 +00:00
Alex Bennée
74d707e2cc fpu/softfloat: re-factor mul
We can now add float16_mul and use the common decompose and
canonicalize functions to have a single implementation for
float16/32/64 versions.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
2018-02-21 10:20:59 +00:00
Alex Bennée
6fff216769 fpu/softfloat: re-factor add/sub
We can now add float16_add/sub and use the common decompose and
canonicalize functions to have a single implementation for
float16/32/64 add and sub functions.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
2018-02-21 10:20:53 +00:00
Alex Bennée
a90119b5a2 fpu/softfloat: define decompose structures
These structures pave the way for generic softfloat helper routines
that will operate on fully decomposed numbers.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
2018-02-21 10:20:45 +00:00
Alex Bennée
d97544c94a fpu/softfloat: move the extract functions to the top of the file
This is pure code-motion during re-factoring as the helpers will be
needed earlier.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
2018-02-21 10:20:39 +00:00
Alex Bennée
210cbd4910 fpu/softfloat: implement float16_squash_input_denormal
This will be required when expanding the MINMAX() macro for 16
bit/half-precision operations.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
2018-02-21 10:20:14 +00:00
Laurent Vivier
0f72129281 softfloat: define floatx80_round()
Add a function to round a floatx80 to the defined precision
(floatx80_rounding_precision)

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
Message-Id: <20170628204241.32106-5-laurent@vivier.eu>
2017-06-29 20:27:39 +02:00
Peter Maydell
d000b477f2 softfloat: Use correct type in float64_to_uint64_round_to_zero()
In float64_to_uint64_round_to_zero() a typo meant that we were
taking the uint64_t return value from float64_to_uint64() and
putting it into an int64_t variable before returning it as
uint64_t again. Use uint64_t instead of pointlessly casting it
back and forth to int64_t.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
2017-02-28 09:03:38 +03:00
Bharata B Rao
fd425037d2 softfloat: Add float128_to_uint32_round_to_zero()
float128_to_uint32_round_to_zero() is needed by xscvqpuwz instruction
of PowerPC ISA 3.0.

Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
2017-02-22 11:28:28 +11:00
Bharata B Rao
2e6d856835 softfloat: Add float128_to_uint64_round_to_zero()
Implement float128_to_uint64() and use that to implement
float128_to_uint64_round_to_zero()

This is required by xscvqpudz instruction of PowerPC ISA 3.0.

Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
2017-02-22 11:28:28 +11:00
Bharata B Rao
9ee6f678f4 softfloat: Add round-to-odd rounding mode
Power ISA 3.0 introduces a few quadruple precision floating point
instructions that support round-to-odd rounding mode. The
round-to-odd mode is explained as under:

Let Z be the intermediate arithmetic result or the operand of a convert
operation. If Z can be represented exactly in the target format, the
result is Z. Otherwise the result is either Z1 or Z2 whichever is odd.
Here Z1 and Z2 are the next larger and smaller numbers representable
in the target format respectively.

Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
2017-02-22 11:28:28 +11:00
Andrew Dutcher
d1eb8f2acb fpu: add mechanism to check for invalid long double formats
All operations that take a floatx80 as an operand need to have their
inputs checked for malformed encodings. In all of these cases, use the
function floatx80_invalid_encoding to perform the check. If an invalid
operand is found, raise an invalid operation exception, and then return
either NaN (for fp-typed results) or the integer indefinite value (the
minimum representable signed integer value, for int-typed results).

For the non-quiet comparison operations, this touches adjacent code in
order to pass style checks.

Signed-off-by: Andrew Dutcher <andrew@andrewdutcher.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1471392895-17324-1-git-send-email-andrew@andrewdutcher.com
[PMM: changed "1 << 63" to "1ULL << 63" to fix compile errors]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2016-09-15 12:43:18 +01:00
Aleksandar Markovic
af39bc8c49 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.

Signed-off-by: Thomas Schwinge <thomas@codesourcery.com>
Signed-off-by: Maciej W. Rozycki <macro@codesourcery.com>
Signed-off-by: Aleksandar Markovic <aleksandar.markovic@imgtec.com>
Tested-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Reviewed-by: Leon Alrae <leon.alrae@imgtec.com>
Tested-by: Leon Alrae <leon.alrae@imgtec.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
[leon.alrae@imgtec.com:
 * cherry-picked 2 chunks from patch #2 to fix compilation warnings]
Signed-off-by: Leon Alrae <leon.alrae@imgtec.com>
2016-06-24 13:40:37 +01:00
Peter Maydell
0c48262d47 fpu: Use plain 'int' rather than 'int_fast16_t' for exponents
Use the plain 'int' type rather than 'int_fast16_t' for handling
exponents. Exponents don't need to be exactly 16 bits, so using int16_t
for them would confuse more than it clarified.

This should be a safe change because int_fast16_t semantics
permit use of 'int' (and on 32-bit glibc that is what you get).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
Message-id: 1453807806-32698-4-git-send-email-peter.maydell@linaro.org
2016-02-19 16:27:22 +00:00
Peter Maydell
07d792d2b0 fpu: Use plain 'int' rather than 'int_fast16_t' for shift counts
Use the plain 'int' type rather than 'int_fast16_t' for shift counts
in the various shift related functions, since we don't actually care
about the size of the integer at all here, and using int16_t would
be confusing.

This should be a safe change because int_fast16_t semantics
permit use of 'int' (and on 32-bit glibc that is what you get).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
Message-id: 1453807806-32698-3-git-send-email-peter.maydell@linaro.org
2016-02-19 16:27:22 +00:00