Most x87 instruction implementations fail to raise the expected IEEE
floating-point exceptions because they do nothing to convert the
exception state from the softfloat machinery into the exception flags
in the x87 status word. There is special-case handling of division to
raise the divide-by-zero exception, but that handling is itself buggy:
it raises the exception in inappropriate cases (inf / 0 and nan / 0,
which should not raise any exceptions, and 0 / 0, which should raise
"invalid" instead).
Fix this by converting the floating-point exceptions raised during an
operation by the softfloat machinery into exceptions in the x87 status
word (passing through the existing fpu_set_exception function for
handling related to trapping exceptions). There are special cases
where some functions convert to integer internally but exceptions from
that conversion are not always correct exceptions for the instruction
to raise.
There might be scope for some simplification if the softfloat
exception state either could always be assumed to be in sync with the
state in the status word, or could always be ignored at the start of
each instruction and just set to 0 then; I haven't looked into that in
detail, and it might run into interactions with the various ways the
emulation does not yet handle trapping exceptions properly. I think
the approach taken here, of saving the softfloat state, setting
exceptions there to 0 and then merging the old exceptions back in
after carrying out the operation, is conservatively safe
Backports commit 975af797f1e04e4d1b1a12f1731141d3770fdbce from qemu
The fist / fistt family of instructions should all store the most
negative integer in the destination format when the rounded /
truncated integer result is out of range or the input is an invalid
encoding, infinity or NaN. The fisttpl and fisttpll implementations
(32-bit and 64-bit results, truncate towards zero) failed to do this,
producing the most positive integer in some cases instead. Fix this
by copying the code used to handle this issue for fistpl and fistpll,
adjusted to use the _round_to_zero functions for the actual
conversion (but without any other changes to that code).
Backports commit c8af85b10c818709755f5dc8061c69920611fd4c from qemu
The fbstp implementation fails to check for out-of-range and invalid
values, instead just taking the result of conversion to int64_t and
storing its sign and low 18 decimal digits. Fix this by checking for
an out-of-range result (invalid conversions always result in INT64_MAX
or INT64_MIN from the softfloat code, which are large enough to be
considered as out-of-range by this code) and storing the packed BCD
indefinite encoding in that case.
Backports commit 374ff4d0a3c2cce2bc6e4ba8a77eaba55c165252 from qemu
The fbstp implementation stores +0 when the rounded result should be
-0 because it compares an integer value with 0 to determine the sign.
Fix this by checking the sign bit of the operand instead.
Backports commit 18c53e1e73197a24f9f4b66b1276eb9868db5bf0 from qemu
The fxam implementation does not check for invalid encodings, instead
treating them like NaN or normal numbers depending on the exponent.
Fix it to check that the high bit of the significand is set before
treating an encoding as NaN or normal, thus resulting in correct
handling (all of C0, C2 and C3 cleared) for invalid encodings.
Backports commit 34b9cc076ff423023a779a04a9f7cd7c17372cbf from qemu
The implementations of the fldl2t, fldl2e, fldpi, fldlg2 and fldln2
instructions load fixed constants independent of the rounding mode.
Fix them to load a value correctly rounded for the current rounding
mode (but always rounded to 64-bit precision independent of the
precision control, and without setting "inexact") as specified.
Backports commit 80b4008c805ebcfd4c0d302ac31c1689e34571e0 from qemu
The fscale implementation uses floatx80_scalbn for the final scaling
operation. floatx80_scalbn ends up rounding the result using the
dynamic rounding precision configured for the FPU. But only a limited
set of x87 floating-point instructions are supposed to respect the
dynamic rounding precision, and fscale is not in that set. Fix the
implementation to save and restore the rounding precision around the
call to floatx80_scalbn.
Backports commit c535d68755576bfa33be7aef7bd294a601f776e0 from qemu
The fscale implementation passes infinite exponents through to generic
code that rounds the exponent to a 32-bit integer before using
floatx80_scalbn. In round-to-nearest mode, and ignoring exceptions,
this works in many cases. But it fails to handle the special cases of
scaling 0 by a +Inf exponent or an infinity by a -Inf exponent, which
should produce a NaN, and because it produces an inexact result for
finite nonzero numbers being scaled, the result is sometimes incorrect
in other rounding modes. Add appropriate handling of infinite
exponents to produce a NaN or an appropriately signed exact zero or
infinity as a result
Backports commit c1c5fb8f9067c830e36830c2b82c0ec146c03d7b from qemu
The fscale implementation does not check for invalid encodings in the
exponent operand, thus treating them like INT_MIN (the value returned
for invalid encodings by floatx80_to_int32_round_to_zero). Fix it to
treat them similarly to signaling NaN exponents, thus generating a
quiet NaN result.
Backports commit b40eec96b26028b68c3594fbf34b6d6f029df26a from qemu
The implementation of the fscale instruction returns a NaN exponent
unchanged. Fix it to return a quiet NaN when the provided exponent is
a signaling NaN.
Backports commit 0d48b436327955c69e2eb53f88aba9aa1e0dbaa0 from qemu
The implementation of the fxtract instruction treats all nonzero
operands as normal numbers, so yielding incorrect results for invalid
formats, infinities, NaNs and subnormal and pseudo-denormal operands.
Implement appropriate handling of all those cases.
Backports commit c415f2c58296d86e9abb7e4a133111acf7031da3 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
The fxam instruction returns the wrong result after fdecstp or after
an underflow. Check fptags to handle this.
Backports commit 93c3593ad04f2610fd0a176dfa89a7e40b6afe1f from qemu
Cleanup in the boilerplate that each target must define.
Replace x86_env_get_cpu with env_archcpu. The combination
CPU(x86_env_get_cpu) should have used ENV_GET_CPU to begin;
use env_cpu now.
Backports commit 6aa9e42f27331be34e06d4d66f92f2272868f96a from qemu
As cpu.h is another typically widely included file which doesn't need
full access to the softfloat API we can remove the includes from here
as well. Where they do need types it's typically for float_status and
the rounding modes so we move that to softfloat-types.h as well.
As a result of not having softfloat in every cpu.h call we now need to
add it to various helpers that do need the full softfloat.h
definitions.
Backports commit 24f91e81b65fcdd0552d1f0fcb0ea7cfe3829c19 from qemu
Move cpu_get_fp80()/cpu_set_fp80() from fpu_helper.c to
machine.c because fpu_helper.c will be disabled if tcg is
disabled in the build.
Backports commit db573d2cf7ae6b5a4fc324be6f55e078fc218464 from qemu.
In unicorn's case, they can be moved into unicorn.c
We've currently got 18 architectures in QEMU, and thus 18 target-xxx
folders in the root folder of the QEMU source tree. More architectures
(e.g. RISC-V, AVR) are likely to be included soon, too, so the main
folder of the QEMU sources slowly gets quite overcrowded with the
target-xxx folders.
To disburden the main folder a little bit, let's move the target-xxx
folders into a dedicated target/ folder, so that target-xxx/ simply
becomes target/xxx/ instead.
Backports commit fcf5ef2ab52c621a4617ebbef36bf43b4003f4c0 from qemu
2018-03-01 22:50:58 -05:00
Renamed from qemu/target-i386/fpu_helper.c (Browse further)
