Because floatx80 has an explicit integer bit, this permits some
odd encodings where the integer bit is not set correctly for the
floating point value type. In In Intel terminology the
categories are:
exp == 0, int = 0, mantissa == 0 : zeroes
exp == 0, int = 0, mantissa != 0 : denormals
exp == 0, int = 1 : pseudo-denormals
0 < exp < 0x7fff, int = 0 : unnormals
0 < exp < 0x7fff, int = 1 : normals
exp == 0x7fff, int = 0, mantissa == 0 : pseudo-infinities
exp == 0x7fff, int = 1, mantissa == 0 : infinities
exp == 0x7fff, int = 0, mantissa != 0 : pseudo-NaNs
exp == 0x7fff, int = 1, mantissa == 0 : NaNs
The usual IEEE cases of zero, denormal, normal, inf and NaN are always valid.
x87 permits as input also pseudo-denormals.
m68k permits all those and also pseudo-infinities, pseudo-NaNs and unnormals.
Currently we have an ifdef in floatx80_invalid_encoding() to select
the x86 vs m68k behaviour. Add new floatx80_behaviour flags to
select whether pseudo-NaN and unnormal are valid, and use these
(plus the existing pseudo_inf_valid flag) to decide whether these
encodings are invalid at runtime.
We leave pseudo-denormals as always-valid, since both x86 and m68k
accept them.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20250224111524.1101196-8-peter.maydell@linaro.org
Message-id: 20250217125055.160887-6-peter.maydell@linaro.org
The definition of which floatx80 encodings are invalid is
target-specific. Currently we handle this with an ifdef, but we
would like to defer this decision to runtime. In preparation, pass a
float_status argument to floatx80_invalid_encoding().
We will change the implementation from ifdef to looking at
the status argument in the following commit.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20250224111524.1101196-7-peter.maydell@linaro.org
In Intel terminology, a floatx80 Infinity with the explicit integer
bit clear is a "pseudo-infinity"; for x86 these are not valid
infinity values. m68k is looser and does not care whether the
Integer bit is set or clear in an infinity.
Move this setting to runtime rather than using an ifdef in
floatx80_is_infinity().
Since this was the last use of the floatx80_infinity global constant,
we remove it and its definition here.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20250224111524.1101196-6-peter.maydell@linaro.org
Message-id: 20250217125055.160887-5-peter.maydell@linaro.org
Unlike the other float formats, whether a floatx80 value is
considered to be an Infinity is target-dependent. (On x86 if the
explicit integer bit is clear this is a "pseudo-infinity" and not a
valid infinity; m68k does not care about the value of the integer
bit.)
Currently we select this target-specific logic at compile time with
an ifdef. We're going to want to do this at runtime, so change the
floatx80_is_infinity() function to take a float_status.
This commit doesn't change any logic; we'll do that in the
next commit.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20250224111524.1101196-5-peter.maydell@linaro.org
Currently we hardcode at compile time whether the floatx80 default
Infinity value has the explicit integer bit set or not (x86 sets it;
m68k does not). To be able to compile softfloat once for all targets
we'd like to move this setting to runtime.
Define a new FloatX80Behaviour enum which is a set of flags that
define the target's floatx80 handling. Initially we define just one
flag, for whether the default Infinity has the Integer bit set or
not, but we will expand this in future commits to cover the other
floatx80 target specifics that we currently make compile-time
settings.
Define a new function floatx80_default_inf() which returns the
appropriate default Infinity value of the given sign, and use it in
the code that was previously directly using the compile-time constant
floatx80_infinity_{low,high} values when packing an infinity into a
floatx80.
Since floatx80 is highly unlikely to be supported in any new
architecture, and the existing code is generally written as "default
to like x87, with an ifdef for m68k", we make the default value for
the floatx80 behaviour flags be "what x87 does". This means we only
need to change the m68k target to specify the behaviour flags.
(Other users of floatx80 are the Arm NWFPE emulation, which is
obsolete and probably not actually doing the right thing anyway, and
the PPC xsrqpxp insn. Making the default be "like x87" avoids our
needing to review and test for behaviour changes there.)
We will clean up the remaining uses of the floatx80_infinity global
constant in subsequent commits.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20250224111524.1101196-2-peter.maydell@linaro.org
Message-id: 20250217125055.160887-2-peter.maydell@linaro.org
Certain Hexagon instructions suppress changes to the result
when the product of fma() is a true zero.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
We currently have a flag, float_muladd_halve_result, to scale
the result by 2**-1. Extend this to handle arbitrary scaling.
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
These variants take a float64 as input, compute the result to
infinite precision (as we do with FloatParts), round the result
to the precision and dynamic range of float32, and then return
the result in the format of float64.
This is the operation PowerPC requires for its float32 operations.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20211119160502.17432-28-richard.henderson@linaro.org>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
For "fmax/fmin ft0, ft1, ft2" and if one of the inputs is sNaN,
The original logic:
Return NaN and set invalid flag if ft1 == sNaN || ft2 == sNan.
The alternative path:
Set invalid flag if ft1 == sNaN || ft2 == sNaN.
Return NaN only if ft1 == NaN && ft2 == NaN.
The IEEE 754 spec allows both implementation and some architecture such
as riscv choose different defintions in two spec versions.
(riscv-spec-v2.2 use original version, riscv-spec-20191213 changes to
alternative)
Signed-off-by: Chih-Min Chao <chihmin.chao@sifive.com>
Signed-off-by: Frank Chang <frank.chang@sifive.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20211021160847.2748577-2-frank.chang@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
The float128 implementation is straight-forward.
Unfortuantely, we don't have any tests we can simply adjust/unlock.
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20210517142739.38597-24-david@redhat.com>
[rth: Update for changed parts_minmax return value]
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This patch implements operations for bfloat16 except conversion and some misc
operations. We also add FloatFmt and pack/unpack interfaces for bfloat16.
As they are both static fields, we can't make a sperate patch for them.
Signed-off-by: LIU Zhiwei <zhiwei_liu@c-sky.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20200813071421.2509-2-zhiwei_liu@c-sky.com>
[rth: Use FloatRelation for comparison operations.]
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
