Depending on the host abi, float16, aka uint16_t, values are
passed and returned either zero-extended in the host register
or with garbage at the top of the host register.
The tcg code generator has so far been assuming garbage, as that
matches the x86 abi, but this is incorrect for other host abis.
Further, target/arm has so far been assuming zero-extended results,
so that it may store the 16-bit value into a 32-bit slot with the
high 16-bits already clear.
Rectify both problems by mapping "f16" in the helper definition
to uint32_t instead of (a typedef for) uint16_t. This forces
the host compiler to assume garbage in the upper 16 bits on input
and to zero-extend the result on output.
Backports commit 6c2be133a7478e443c99757b833d0f265c48e0a6 from qemu
The FRECPX instructions should (like most other floating point operations)
honour the FPCR.FZ bit which specifies whether input denormals should
be flushed to zero (or FZ16 for the half-precision version).
We forgot to implement this, which doesn't affect the results (since
the calculation doesn't actually care about the mantissa bits) but did
mean we were failing to set the FPSR.IDC bit.
Backports commit 2cfbf36ec07f7cac1aabb3b86f1c95c8a55424ba from qemu
AMD Zen expose the Intel equivalant to Speculative Store Bypass Disable
via the 0x80000008_EBX[25] CPUID feature bit.
This needs to be exposed to guest OS to allow them to protect
against CVE-2018-3639.
Backports commit 403503b162ffc33fb64cfefdf7b880acf41772cd from qemu
"Some AMD processors only support a non-architectural means of enabling
speculative store bypass disable (SSBD). To allow a simplified view of
this to a guest, an architectural definition has been created through a new
CPUID bit, 0x80000008_EBX[25], and a new MSR, 0xc001011f. With this, a
hypervisor can virtualize the existence of this definition and provide an
architectural method for using SSBD to a guest.
Add the new CPUID feature, the new MSR and update the existing SSBD
support to use this MSR when present." (from x86/speculation: Add virtualized
speculative store bypass disable support in Linux).
Backports commit cfeea0c021db6234c154dbc723730e81553924ff from qemu
New microcode introduces the "Speculative Store Bypass Disable"
CPUID feature bit. This needs to be exposed to guest OS to allow
them to protect against CVE-2018-3639.
Backports commit d19d1f965904a533998739698020ff4ee8a103da from qemu
This patch documents the preference for g_new instead of g_malloc. The
reasons were adapted from commit b45c03f585ea9bb1af76c73e82195418c294919d.
Discussion in QEMU's mailing list:
http://lists.nongnu.org/archive/html/qemu-devel/2018-05/msg03238.html
Backports commit f7c922ed3d8e3cb54febbdc594ce9f4400e0d290 from qemu
Excepting MOVPRFX, which isn't a reduction. Presumably it is
placed within the group because of its encoding.
Backports commit 047cec971d2791b206677b954227ea92ff7ee3db from qemu
These were the instructions that were stubbed out when
introducing the decode skeleton.
Backports commit 39eea56172e668cc4cca611ed9166779df54ac63 from qemu
Including only 4, as-yet unimplemented, instruction patterns
so that the whole thing compiles.
Backports commit 38388f7ee3adc04a7e7246c04352451c4f8d00fb from qemu
This is a preparation for the coming feature of creating dynamically an XML
description for the ARM sysregs.
Add "_S" suffix to the secure version of sysregs that have both S and NS views
Replace (S) and (NS) by _S and _NS for the register that are manually defined,
so all the registers follow the same convention.
Backports commit 9c513e786d85cc58b8ba56a482566f759e0835b6 from qemu
This is a preparation for the coming feature of creating dynamically an XML
description for the ARM sysregs.
A register has ARM_CP_NO_GDB enabled will not be shown in the dynamic XML.
This bit is enabled automatically when creating CP_ANY wildcard aliases.
This bit could be enabled manually for any register we want to remove from the
dynamic XML description.
Backports commit 1f16378718fa87d63f70d0797f4546a88d8e3dd7 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
Isolate the target-specific choice to 2 functions instead of 6.
The code in float16_default_nan was only correct for ARM, MIPS, and X86.
Though float16 support is rare among our targets.
The code in float128_default_nan was arguably wrong for Sparc. While
QEMU supports the Sparc 128-bit insns, no real cpu enables it.
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 value for snan_bit_is_one.
Move routines that no longer have ifdefs out of softfloat-specialize.h.
Backports commit 0218a16e540ad416683e19dfbd52f75092507b27 from qemu
For each operand, pass a single enumeration instead of a pair of booleans.
The commit also merges multiple different ifdef-selected implementations
of pickNaNMulAdd into a single function whose body is ifdef-selected.
Backports commit 3bd2dec1a1e8fadb49e3ff2e2633f79e01a25c41 from qemu
For each operand, pass a single enumeration instead of a pair of booleans.
The commit also merges multiple different ifdef-selected implementations
of pickNaN into a single function whose body is ifdef-selected.
Backports commit 4f251cfd52c7945ebd6ab0d86518b1a9aa51b10c from qemu
We will need these helpers within softfloat-specialize.h, so move
the definitions above the include. After specialization, they will
not always be used so mark them to avoid the Werror.
Backports commit 247d1f2190c5530fd18fe92a145d0a1985fca4e4 from qemu
Only MIPS requires snan_bit_is_one to be variable. While we are
specializing softfloat behaviour, allow other targets to eliminate
this runtime check.
Backports commit 03385dfdaaa2dc31bbd07d13244a6b037bfab4cc from qemu
This allows us to delete a lot of additional boilerplate
code which is no longer needed.
Backports commit 6fed16b265a4fcc810895bbca4d67e1ae7a89f07 from qemu
For float16 ARM supports an alternative half-precision format which
sacrifices the ability to represent NaN/Inf in return for a higher
dynamic range. The new FloatFmt flag, arm_althp, is then used to
modify the behaviour of canonicalize and round_canonical with respect
to representation and exception raising.
Usage of this new flag waits until we re-factor float-to-float conversions.
Backports commit ca3a3d5a3141d44aa717dc11e4d33a834a85e1f6 from qemu
The ARM ARM specifies FZ16 is suppressed for conversions. Rather than
pushing this logic into the softfloat code we can simply save the FZ
state and temporarily disable it for the softfloat call.
Backports commit 0acb9e7cb341cd767e39ec0875c8706eb2f1c359 from qemu
Instead of passing env and leaving it up to the helper to get the
right fpstatus we pass it explicitly. There was already a get_fpstatus
helper for neon for the 32 bit code. We also add an get_ahp_flag() for
passing the state of the alternative FP16 format flag. This leaves
scope for later tracking the AHP state in translation flags.
Backports commit 486624fcd3eaca6165ab8401d73bbae6c0fb81c1 from qemu
