Currently we handle flushing of output denormals in uncanon_normal
always before we deal with rounding. This works for architectures
that detect tininess before rounding, but is usually not the right
place when the architecture detects tininess after rounding. For
example, for x86 the SDM states that the MXCSR FTZ control bit causes
outputs to be flushed to zero "when it detects a floating-point
underflow condition". This means that we mustn't flush to zero if
the input is such that after rounding it is no longer tiny.
At least one of our guest architectures does underflow detection
after rounding but flushing of denormals before rounding (MIPS MSA);
this means we need to have a config knob for this that is separate
from our existing tininess_before_rounding setting.
Add an ftz_detection flag. For consistency with
tininess_before_rounding, we make it default to "detect ftz after
rounding"; this means that we need to explicitly set the flag to
"detect ftz before rounding" on every existing architecture that sets
flush_to_zero, so that this commit has no behaviour change.
(This means more code change here but for the long term a less
confusing API.)
For several architectures the current behaviour is either
definitely or possibly wrong; annotate those with TODO comments.
These architectures are definitely wrong (and should detect
ftz after rounding):
* x86
* Alpha
For these architectures the spec is unclear:
* MIPS (for non-MSA)
* RX
* SH4
PA-RISC makes ftz detection IMPDEF, but we aren't setting the
"tininess before rounding" setting that we ought to.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Set the default NaN pattern explicitly for the tests/fp code.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-36-peter.maydell@linaro.org
Explicitly set a rule in the softfloat tests for propagating NaNs in
the muladd case. In meson.build we put -DTARGET_ARM in fpcflags, and
so we should select here the Arm rule of float_3nan_prop_s_cab.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-17-peter.maydell@linaro.org
Explicitly set a rule in the softfloat tests for the inf-zero-nan
muladd special case. In meson.build we put -DTARGET_ARM in fpcflags,
and so we should select here the Arm rule of
float_infzeronan_dnan_if_qnan.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20241202131347.498124-5-peter.maydell@linaro.org
Explicitly set a 2-NaN propagation rule in the softfloat tests. In
meson.build we put -DTARGET_ARM in fpcflags, and so we should select
here the Arm propagation rule of float_2nan_prop_s_ab.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241025141254.2141506-3-peter.maydell@linaro.org
G_NORETURN was introduced in glib 2.68, fallback to G_GNUC_NORETURN in
glib-compat.
Note that this attribute must be placed before the function declaration
(bringing a bit of consistency in qemu codebase usage).
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Warner Losh <imp@bsdimp.com>
Message-Id: <20220420132624.2439741-20-marcandre.lureau@redhat.com>
Rename to parts$N_muladd.
Implement float128_muladd with FloatParts128.
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Currently this only support softfloat calculations because working out
if the hardware supports 128 bit floats needs configure magic. The 3
op muladd operation is currently unimplemented so commented out for
now.
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20201020163738.27700-8-alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
At this point random_ops[] only contains normals, so there's
no need to do anything to them. In fact, raising the exponent
here can make the output !normal, which is precisely
what the comment says we want to avoid.
Signed-off-by: Emilio G. Cota <cota@braap.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
The second test in the branches is wrong; fix while converting
to a switch statement, which is easier to get right.
Signed-off-by: Emilio G. Cota <cota@braap.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
These microbenchmarks will allow us to measure the performance impact of
FP emulation optimizations. Note that we can measure both directly the impact
on the softfloat functions (with "-t soft"), or the impact on an
emulated workload (call with "-t host" and run under qemu user-mode).
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>
