Inline pickNaN into its only caller. This makes one assert
redundant with the immediately preceding IF.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20241203203949.483774-9-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Unpacking and repacking the parts may be slightly more work
than we did before, but we get to reuse more code. For a
code path handling exceptional values, this is an improvement.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241203203949.483774-8-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
This function is part of the public interface and
is not "specialized" to any target in any way.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20241203203949.483774-7-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
While all indices into val[] should be in [0-2], the mask
applied is two bits. To help static analysis see there is
no possibility of read beyond the end of the array, pad the
array to 4 entries, with the final being (implicitly) NULL.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20241203203949.483774-6-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Assign the pointer return value to 'a' directly,
rather than going through an intermediary index.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20241203203949.483774-5-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Remove "3" as a special case for which and simply
branch to return the desired value.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20241203203949.483774-4-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Inline pickNaNMulAdd into its only caller. This makes
one assert redundant with the immediately preceding IF.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20241203203949.483774-3-richard.henderson@linaro.org
[PMM: keep comment from old code in new location]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Now that all our targets have bene converted to explicitly specify
their pattern for the default NaN value we can remove the remaining
fallback code in parts64_default_nan().
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-55-peter.maydell@linaro.org
Set the default NaN pattern explicitly for tricore.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-54-peter.maydell@linaro.org
Set the default NaN pattern explicitly for riscv.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-53-peter.maydell@linaro.org
Set the default NaN pattern explicitly for hexagon.
Remove the ifdef from parts64_default_nan(); the only
remaining unconverted targets all use the default case.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-52-peter.maydell@linaro.org
Set the default NaN pattern explicitly for xtensa.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-51-peter.maydell@linaro.org
Set the default NaN pattern explicitly for SPARC, and remove
the ifdef from parts64_default_nan.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-50-peter.maydell@linaro.org
Set the default NaN pattern explicitly for s390x.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-49-peter.maydell@linaro.org
Set the default NaN pattern explicitly for rx.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-48-peter.maydell@linaro.org
Set the default NaN pattern explicitly for sh4. Note that sh4
is one of the only three targets (the others being HPPA and
sometimes MIPS) that has snan_bit_is_one set.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-47-peter.maydell@linaro.org
Set the default NaN pattern explicitly for ppc.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-46-peter.maydell@linaro.org
Set the default NaN pattern explicitly for openrisc.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-45-peter.maydell@linaro.org
Set the default NaN pattern explicitly for MIPS. Note that this
is our only target which currently changes the default NaN
at runtime (which it was previously doing indirectly when it
changed the snan_bit_is_one setting).
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-44-peter.maydell@linaro.org
Set the default NaN pattern explicitly for m68k.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-43-peter.maydell@linaro.org
Set the default NaN pattern explicitly for loongarch.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-42-peter.maydell@linaro.org
Set the default NaN pattern explicitly for the arm target.
This includes setting it for the old linux-user nwfpe emulation.
For nwfpe, our default doesn't match the real kernel, but we
avoid making a behaviour change in this commit.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-41-peter.maydell@linaro.org
Set the default NaN pattern explicitly for the alpha target.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-40-peter.maydell@linaro.org
Set the default NaN pattern explicitly, and remove the ifdef from
parts64_default_nan().
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-39-peter.maydell@linaro.org
Set the default NaN pattern explicitly, and remove the ifdef from
parts64_default_nan().
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-38-peter.maydell@linaro.org
Set the default NaN pattern explicitly, and remove the ifdef from
parts64_default_nan().
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-37-peter.maydell@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
Currently we hardcode the default NaN value in parts64_default_nan()
using a compile-time ifdef ladder. This is awkward for two cases:
* for single-QEMU-binary we can't hard-code target-specifics like this
* for Arm FEAT_AFP the default NaN value depends on FPCR.AH
(specifically the sign bit is different)
Add a field to float_status to specify the default NaN value; fall
back to the old ifdef behaviour if these are not set.
The default NaN value is specified by setting a uint8_t to a
pattern corresponding to the sign and upper fraction parts of
the NaN; the lower bits of the fraction are set from bit 0 of
the pattern.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-35-peter.maydell@linaro.org
Now that float_status has a bunch of fp parameters,
it is easier to copy an existing structure than create
one from scratch. Begin by copying the structure that
corresponds to the FPSR and make only the adjustments
required for BFloat16 semantics.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20241203203949.483774-2-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
In the helper_compute_fprf functions, we pass a dummy float_status
in to the is_signaling_nan() function. This is unnecessary, because
we have convenient access to the CPU env pointer here and that
is already set up with the correct values for the snan_bit_is_one
and no_signaling_nans config settings. is_signaling_nan() doesn't
ever update the fp_status with any exception flags, so there is
no reason not to use env->fp_status here.
Use env->fp_status instead of the dummy fp_status.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-34-peter.maydell@linaro.org
In the helper functions flcmps and flcmpd we use a scratch float_status
so that we don't change the CPU state if the comparison raises any
floating point exception flags. Instead of zero-initializing this
scratch float_status, initialize it as a copy of env->fp_status. This
avoids the need to explicitly initialize settings like the NaN
propagation rule or others we might add to softfloat in future.
To do this we need to pass the CPU env pointer in to the helper.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-33-peter.maydell@linaro.org
In cf_fpu_gdb_get_reg() and cf_fpu_gdb_set_reg() we do the conversion
from float64 to floatx80 using a scratch float_status, because we
don't want the conversion to affect the CPU's floating point exception
status. Currently we use a zero-initialized float_status. This will
get steadily more awkward as we add config knobs to float_status
that the target must initialize. Avoid having to add any of that
configuration here by instead initializing our local float_status
from the env->fp_status.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-32-peter.maydell@linaro.org
In the frem helper, we have a local float_status because we want to
execute the floatx80_div() with a custom rounding mode. Instead of
zero-initializing the local float_status and then having to set it up
with the m68k standard behaviour (including the NaN propagation rule
and copying the rounding precision from env->fp_status), initialize
it as a complete copy of env->fp_status. This will avoid our having
to add new code in this function for every new config knob we add
to fp_status.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-31-peter.maydell@linaro.org
In target/loongarch's helper_fclass_s() and helper_fclass_d() we pass
a zero-initialized float_status struct to float32_is_quiet_nan() and
float64_is_quiet_nan(), with the cryptic comment "for
snan_bit_is_one".
This pattern appears to have been copied from target/riscv, where it
is used because the functions there do not have ready access to the
CPU state struct. The comment presumably refers to the fact that the
main reason the is_quiet_nan() functions want the float_state is
because they want to know about the snan_bit_is_one config.
In the loongarch helpers, though, we have the CPU state struct
to hand. Use the usual env->fp_status here. This avoids our needing
to track that we need to update the initializer of the local
float_status structs when the core softfloat code adds new
options for targets to configure their behaviour.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-30-peter.maydell@linaro.org
We create our 128-bit default NaN by calling parts64_default_nan()
and then adjusting the result. We can do the same trick for creating
the floatx80 default NaN, which lets us drop a target ifdef.
floatx80 is used only by:
i386
m68k
arm nwfpe old floating-point emulation emulation support
(which is essentially dead, especially the parts involving floatx80)
PPC (only in the xsrqpxp instruction, which just rounds an input
value by converting to floatx80 and back, so will never generate
the default NaN)
The floatx80 default NaN as currently implemented is:
m68k: sign = 0, exp = 1...1, int = 1, frac = 1....1
i386: sign = 1, exp = 1...1, int = 1, frac = 10...0
These are the same as the parts64_default_nan for these architectures.
This is technically a possible behaviour change for arm linux-user
nwfpe emulation emulation, because the default NaN will now have the
sign bit clear. But we were already generating a different floatx80
default NaN from the real kernel emulation we are supposedly
following, which appears to use an all-bits-1 value:
https://elixir.bootlin.com/linux/v6.12/source/arch/arm/nwfpe/softfloat-specialize#L267
This won't affect the only "real" use of the nwfpe emulation, which
is ancient binaries that used it as part of the old floating point
calling convention; that only uses loads and stores of 32 and 64 bit
floats, not any of the floatx80 behaviour the original hardware had.
We also get the nwfpe float64 default NaN value wrong:
https://elixir.bootlin.com/linux/v6.12/source/arch/arm/nwfpe/softfloat-specialize#L166
so if we ever cared about this obscure corner the right fix would be
to correct that so nwfpe used its own default-NaN setting rather
than the Arm VFP one.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-29-peter.maydell@linaro.org
Currently m68k_cpu_reset_hold() calls floatx80_default_nan(NULL)
to get the NaN bit pattern to reset the FPU registers. This
works because it happens that our implementation of
floatx80_default_nan() doesn't actually look at the float_status
pointer except for TARGET_MIPS. However, this isn't guaranteed,
and to be able to remove the ifdef in floatx80_default_nan()
we're going to need a real float_status here.
Rearrange m68k_cpu_reset_hold() so that we initialize env->fp_status
earlier, and thus can pass it to floatx80_default_nan().
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-28-peter.maydell@linaro.org
The use_first_nan field in float_status was an xtensa-specific way to
select at runtime from two different NaN propagation rules. Now that
xtensa is using the target-agnostic NaN propagation rule selection
that we've just added, we can remove use_first_nan, because there is
no longer any code that reads it.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-27-peter.maydell@linaro.org
Set the Float3NaNPropRule explicitly for HPPA, and remove the
ifdef from pickNaNMulAdd().
HPPA is the only target that was using the default branch of the
ifdef ladder (other targets either do not use muladd or set
default_nan_mode), so we can remove the ifdef fallback entirely now
(allowing the "rule not set" case to fall into the default of the
switch statement and assert).
We add a TODO note that the HPPA rule is probably wrong; this is
not a behavioural change for this refactoring.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-26-peter.maydell@linaro.org
Set the Float3NaNPropRule explicitly for i386. We had no
i386-specific behaviour in the old ifdef ladder, so we were using the
default "prefer a then b then c" fallback; this is actually the
correct per-the-spec handling for i386.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-25-peter.maydell@linaro.org
Set the Float3NaNPropRule explicitly for xtensa, and remove the
ifdef from pickNaNMulAdd().
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-24-peter.maydell@linaro.org
Set the Float3NaNPropRule explicitly for Arm, and remove the
ifdef from pickNaNMulAdd().
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-23-peter.maydell@linaro.org
Set the Float3NaNPropRule explicitly for SPARC, and remove the
ifdef from pickNaNMulAdd().
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-22-peter.maydell@linaro.org
Set the Float3NaNPropRule explicitly for s390x, and remove the
ifdef from pickNaNMulAdd().
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-21-peter.maydell@linaro.org
Set the Float3NaNPropRule explicitly for PPC, and remove the
ifdef from pickNaNMulAdd().
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-20-peter.maydell@linaro.org
Set the Float3NaNPropRule explicitly for loongarch, and remove the
ifdef from pickNaNMulAdd().
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-19-peter.maydell@linaro.org
Set the Float3NaNPropRule explicitly for Arm, and remove the
ifdef from pickNaNMulAdd().
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-18-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
IEEE 758 does not define a fixed rule for which NaN to pick as the
result if both operands of a 3-operand fused multiply-add operation
are NaNs. As a result different architectures have ended up with
different rules for propagating NaNs.
QEMU currently hardcodes the NaN propagation logic into the binary
because pickNaNMulAdd() has an ifdef ladder for different targets.
We want to make the propagation rule instead be selectable at
runtime, because:
* this will let us have multiple targets in one QEMU binary
* the Arm FEAT_AFP architectural feature includes letting
the guest select a NaN propagation rule at runtime
In this commit we add an enum for the propagation rule, the field in
float_status, and the corresponding getters and setters. We change
pickNaNMulAdd to honour this, but because all targets still leave
this field at its default 0 value, the fallback logic will pick the
rule type with the old ifdef ladder.
It's valid not to set a propagation rule if default_nan_mode is
enabled, because in that case there's no need to pick a NaN; all the
callers of pickNaNMulAdd() catch this case and skip calling it.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-16-peter.maydell@linaro.org
The new implementation of pickNaNMulAdd() will find it convenient
to know whether at least one of the three arguments to the muladd
was a signaling NaN. We already calculate that in the caller,
so pass it in as a new bool have_snan.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-15-peter.maydell@linaro.org
Set the FloatInfZeroNaNRule explicitly for the HPPA target,
so we can remove the ifdef from pickNaNMulAdd().
As this is the last target to be converted to explicitly setting
the rule, we can remove the fallback code in pickNaNMulAdd()
entirely.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-14-peter.maydell@linaro.org
