Both x87 and m68k need the low parts of the quotient for their
remainder operations. Arrange for floatx80_modrem to track those bits
and return them via a pointer.
The architectures using float32_rem and float64_rem do not appear to
need this information, so the *_rem interface is left unchanged and
the information returned only from floatx80_modrem. The logic used to
determine the low 7 bits of the quotient for m68k
(target/m68k/fpu_helper.c:make_quotient) appears completely bogus (it
looks at the result of converting the remainder to integer, the
quotient having been discarded by that point); this patch does not
change that, but the m68k maintainers may wish to do so.
Backports commit 445810ec915687d37b8ae0ef8d7340ab4a153efa from qemu
The floatx80 remainder implementation unnecessarily sets the high bit
of bSig explicitly. By that point in the function, arguments that are
invalid, zero, infinity or NaN have already been handled and
subnormals have been through normalizeFloatx80Subnormal, so the high
bit will already be set. Remove the unnecessary code.
Backports commit 566601f1f9d972e44214696d3cb320e6c18880aa from qemu
The floatx80 remainder implementation sometimes returns the numerator
unchanged when the denominator is sufficiently larger than the
numerator. But if the value to be returned unchanged is a
pseudo-denormal, that is incorrect. Fix it to normalize the numerator
in that case.
Backports commit b662495dca0a2a36008cf8def91e2566519ed3f2 from qemu
The floatx80 remainder implementation ignores the high bit of the
significand when checking whether an operand (numerator) with zero
exponent is zero. This means it mishandles a pseudo-denormal
representation of 0x1p-16382L by treating it as zero. Fix this by
checking the whole significand instead.
Backports commit 499a2f7b554a295cfc10f8cd026d9b20a38fe664 from qemu
The m68k-specific softfloat code includes a function floatx80_mod that
is extremely similar to floatx80_rem, but computing the remainder
based on truncating the quotient toward zero rather than rounding it
to nearest integer. This is also useful for emulating the x87 fprem
and fprem1 instructions. Change the floatx80_rem implementation into
floatx80_modrem that can perform either operation, with both
floatx80_rem and floatx80_mod as thin wrappers available for all
targets.
There does not appear to be any use for the _mod operation for other
floating-point formats in QEMU (the only other architectures using
_rem at all are linux-user/arm/nwfpe, for FPA emulation, and openrisc,
for instructions that have been removed in the latest version of the
architecture), so no change is made to the code for other formats.
Backports commit 6b8b0136ab3018e4b552b485f808bf66bcf19ead from qemu
When building with clang version 10.0.0-4ubuntu1, we get:
CC lm32-softmmu/fpu/softfloat.o
fpu/softfloat.c:3365:13: error: bitwise negation of a boolean expression; did you mean logical negation? [-Werror,-Wbool-operation]
absZ &= ~ ( ( ( roundBits ^ 0x40 ) == 0 ) & roundNearestEven );
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
fpu/softfloat.c:3423:18: error: bitwise negation of a boolean expression; did you mean logical negation? [-Werror,-Wbool-operation]
absZ0 &= ~ ( ( (uint64_t) ( absZ1<<1 ) == 0 ) & roundNearestEven );
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...
fpu/softfloat.c:4273:18: error: bitwise negation of a boolean expression; did you mean logical negation? [-Werror,-Wbool-operation]
zSig1 &= ~ ( ( zSig2 + zSig2 == 0 ) & roundNearestEven );
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Fix by rewriting the fishy bitwise AND of two bools as an int.
Backports commit 4066288694c3bdd175df813cad675a3b5191956b from qemu
Replace the floatx80 compare specializations with inline functions
that call the standard floatx80_compare{,_quiet} functions.
Use bool as the return type.
Backports commit c6baf65000f826a713e8d9b5b35e617b0ca9ab5d from qemu
Replace the float128 compare specializations with inline functions
that call the standard float128_compare{,_quiet} functions.
Use bool as the return type.
Backports commit b7b1ac684fea49c6bfe1ad8b706aed7b09116d15 from qemu
Replace the float64 compare specializations with inline functions
that call the standard float64_compare{,_quiet} functions.
Use bool as the return type.
Backports commit 0673ecdf6cb2b1445a85283db8cbacb251c46516 from qemu
Replace the float32 compare specializations with inline functions
that call the standard float32_compare{,_quiet} functions.
Use bool as the return type.
Backports commit 5da2d2d8e53d80e92a61720ea995c86b33cbf25d from qemu
Give the previously unnamed enum a typedef name. Use it in the
prototypes of compare functions. Use it to hold the results
of the compare functions.
Backports commit 71bfd65c5fcd72f8af2735905415c7ce4220f6dc from qemu
Give the previously unnamed enum a typedef name. Use the packed
attribute so that we do not affect the layout of the float_status
struct. Use it in the prototypes of relevant functions.
Adjust switch statements as necessary to avoid compiler warnings.
Backports commit 3dede407cc61b64997f0c30f6dbf4df09949abc9 from qemu
Slightly tidies the usage within softfloat.c and the
representation in float_status.
Backports commit a828b373bdabc7e53d1e218e3fc76f85b6674688 from qemu
The existing f{32,64}_addsub_post test, which checks for zero
inputs, is identical to f{32,64}_mul_fast_test. Which means
we can eliminate the fast_test/fast_op hooks in favor of
reusing the same post hook.
This means we have one fewer test along the fast path for multiply.
Backports commit b240c9c497b9880ac0ba29465907d5ebecd48083 from qemu
The softfloat function floatx80_round_to_int incorrectly handles the
case of a pseudo-denormal where only the high bit of the significand
is set, ignoring that bit (treating the number as an exact zero)
rather than treating the number as an alternative representation of
+/- 2^-16382 (which may round to +/- 1 depending on the rounding mode)
as hardware does. Fix this check (simplifying the code in the
process).
Backports commit 9ecaf5ccec13ff2e8fe1e72f6e0f3367d2169c1c from qemu
The softfloat floatx80 comparisons fail to allow for pseudo-denormals,
which should compare equal to corresponding values with biased
exponent 1 rather than 0. Add an adjustment for that case when
comparing numbers with the same sign.
Backports commit be53fa785ab766d2722628403edee75b3e6ab599 from qemu
The softfloat function addFloatx80Sigs, used for addition of values
with the same sign and subtraction of values with opposite sign, fails
to handle the case where the two values both have biased exponent zero
and there is a carry resulting from adding the significands, which can
occur if one or both values are pseudo-denormals (biased exponent
zero, explicit integer bit 1). Add a check for that case, so making
the results match those seen on x86 hardware for pseudo-denormals.
Backports commit 41602807766e253ccb6fb761f3ff12767f786e2c from qemu
Conversions between IEEE floating-point formats should convert
signaling NaNs to quiet NaNs. Most of those in QEMU's softfloat code
do so, but those for floatx80 fail to. Fix those conversions to
silence signaling NaNs as well.
Backports commit 7537c2b4a363237534c96d089a02b0712b49d890 from qemu
All other calls to normalize*Subnormal detect zero input before
the call -- this is the only outlier. This case can happen with
+0.0 + +0.0 = +0.0 or -0.0 + -0.0 = -0.0, so return a zero of
the correct sign.
Reported-by: Coverity (CID 1421991)
Backports commit 2f311075b7a74124098effc72290767b02869561 from qemu
This is not a normal header and should only be included in the main
softfloat.c file to bring in the various target specific
specialisations. Indeed as it contains non-inlined C functions it is
not even a legal header. Rename it to match our included C convention.
Backports commit 00f43279a3e5e7ea3a0fa853157863663e838e2e from qemu
In our quest to eliminate the home rolled LIT64 macro we fixup usage
inside the softfloat code. While we are at it we remove some of the
extraneous spaces to closer fit the house style.
Backports commit e932112420f063776f2b9d9e5512830cd6890a7a from qemu
Remove some more use of LIT64 while making the meaning more clear. We
also avoid the need of casts as the results by definition fit into the
return type.
Backports commit 2c217da0fc9f1127bda804e2a500b8138b02c581 from qemu
This also allows us to remove the extractFloat16exp/frac helpers. We
avoid using the floatXX_pack_raw functions as they are slight overkill
for masking out all but the top bit of the number. The generated code
is almost exactly the same as makes no difference to the
pre-conversion code.
Backports commit e6b405fe00d8e6424a58492b37a1656d1ef0929b from qemu
We have a wrapper that does the right thing from stdint.h so lets use
it for our constants in softfloat-specialize.h
Backports commit f7e81a945737631c19405a39d510d2284257c3ff from qemu
Previously this was only supported for roundAndPackFloat64.
New support in round_canonical, round_to_int, float128_round_to_int,
roundAndPackFloat32, roundAndPackInt32, roundAndPackInt64,
roundAndPackUint64. This does not include any of the floatx80 routines,
as we do not have users for that rounding mode there.
Backports commit 5d64abb32ffe558e616545819f3e53dd66335994 from qemu
Handling it just like float128_to_uint32_round_to_zero, that hopefully
is free of bugs :)
Documentation basically copied from float128_to_uint64
Backports commit e45de9922e43c1ce4f4739b62142314a13029d5c from qemu
Clang v7.0.1 does not like the __int128 variable type for inline
assembly on s390x:
In file included from fpu/softfloat.c:97:
include/fpu/softfloat-macros.h:647:9: error: inline asm error:
This value type register class is not natively supported!
asm("dlgr %0, %1" : "+r"(n) : "r"(d));
^
Disable this code part there now when compiling with Clang, so that
the generic code gets used instead.
Backports commit 2c00542c70b9cbd6da510c97cd3d46adcf9e3efc from qemu
Performance results for fp-bench:
Host: Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz
- before:
sqrt-single: 42.30 MFlops
sqrt-double: 22.97 MFlops
- after:
sqrt-single: 311.42 MFlops
sqrt-double: 311.08 MFlops
Here USE_FP makes a huge difference for f64's, with throughput
going from ~200 MFlops to ~300 MFlops.
Backports commit f131bae8a7b7ed1928cc94c69df291db609c316a from qemu
The appended paves the way for leveraging the host FPU for a subset
of guest FP operations. For most guest workloads (e.g. FP flags
aren't ever cleared, inexact occurs often and rounding is set to the
default [to nearest]) this will yield sizable performance speedups.
The approach followed here avoids checking the FP exception flags register.
See the added comment for details.
This assumes that QEMU is running on an IEEE754-compliant FPU and
that the rounding is set to the default (to nearest). The
implementation-dependent specifics of the FPU should not matter; things
like tininess detection and snan representation are still dealt with in
soft-fp. However, this approach will break on most hosts if we compile
QEMU with flags that break IEEE compatibility. There is no way to detect
all of these flags at compilation time, but at least we check for
-ffast-math (which defines __FAST_MATH__) and disable hardfloat
(plus emit a #warning) when it is set.
This patch just adds common code. Some operations will be migrated
to hardfloat in subsequent patches to ease bisection.
Note: some architectures (at least PPC, there might be others) clear
the status flags passed to softfloat before most FP operations. This
precludes the use of hardfloat, so to avoid introducing a performance
regression for those targets, we add a flag to disable hardfloat.
In the long run though it would be good to fix the targets so that
at least the inexact flag passed to softfloat is indeed sticky.
Backports commit a94b783952cc493cb241aabb1da8c7a830385baa from qemu
glibc >= 2.25 defines canonicalize in commit eaf5ad0
(Add canonicalize, canonicalizef, canonicalizel., 2016-10-26).
Given that we'll be including <math.h> soon, prepare
for this by prefixing our canonicalize() with sf_ to avoid
clashing with the libc's canonicalize().
Backports commit f9943c7f766678af36d31076b78e466256f4871b from qemu
The divdeu instruction was added to ISA 2.06 (Power7).
Exclude this block from older cpus.
Fixes: 27ae5109a2ba (softfloat: Specialize udiv_qrnnd for ppc64)
Backports commit 7370981bd1ef58b3c20ba8b83cc342d1c61bc773 from qemu
The ISA has a 128/64-bit division instruction, though it assumes the
low 64-bits of the numerator are 0, and so requires a bit more fixup
than a full 128-bit division insn.
Backports commit 27ae5109a2ba8b6b679cce3e03e16570a34390a0 from qemu
The __udiv_qrnnd primitive that we nicked from gmp requires its
inputs to be normalized. We were not doing that. Because the
inputs are nearly normalized already, finishing that is trivial.
Replace div128to64 with a "proper" udiv_qrnnd, so that this
remains a reusable primitive.
Fixes: cf07323d494
Fixes: https://bugs.launchpad.net/qemu/+bug/1793119
Backports commit 5dfbc9e4903c0121140f2945f05df48cea72dd82 from qemu
Our minimum required compiler for compiling QEMU is GCC 4.1 these days,
so we can drop the support for compilers which do not provide the
__builtin_clz*() functions yet. Since the countLeadingZeros32/64 are
then identical to the clz32/64 functions, and we do not have to sync
the softloat 2 codebase with upstream anymore (softloat 3 is a complete
rewrite) we can simply replace the functions with our QEMU versions.
Backports commit 0019d5c3a18c31604fb55f9cec3ceb13999c4866 from qemu
It has not had users since f83311e476 ("target-m68k: use floatx80
internally", 2017-06-21).
Note that no other bit-width has floatX_trunc_to_int.
Backports commit c953da8f0be5e026d1c9128660736d72294feb3e from qemu
For 0x1.0000000000003p+0 + 0x1.ffffffep+14 = 0x1.0001fffp+15
we dropped the sticky bit and so failed to raise inexact.
Backports commit 64d450a0eaad5f02f9d6bba1dd451446297bb4dc from qemu
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.
Backports commit 377ed92679a2a5f838bc0a095112ea5020720fff from qemu
Reduce the number of ifdefs. Correct the result for OpenRISC
and TriCore (although TriCore fixed in target-specific code).
Backports commit 8fb3d90203f328d1bebcf7f20934027bfc4e7f3f from qemu
