History log of /openbmc/qemu/tests/tcg/i386/test-i386-fyl2xp1.c (Results 1 – 2 of 2)
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Revision tags: v9.2.0, v9.1.2, v9.1.1, v9.1.0, v8.0.0, v7.2.0, v7.0.0, v6.2.0, v6.1.0, v5.2.0
# 3591ddd3 26-Jun-2020 Peter Maydell <peter.maydell@linaro.org>

Merge remote-tracking branch 'remotes/bonzini/tags/for-upstream' into staging

* Various fixes
* libdaxctl support to correctly align devdax character devices (Jingqi)
* initial-all-set support for l

Merge remote-tracking branch 'remotes/bonzini/tags/for-upstream' into staging

* Various fixes
* libdaxctl support to correctly align devdax character devices (Jingqi)
* initial-all-set support for live migration (Jay)
* forbid '-numa node, mem' for 5.1 and newer machine types (Igor)
* x87 fixes (Joseph)
* Tighten memory_region_access_valid (Michael) and fix fallout (myself)
* Replay fixes (Pavel)

# gpg: Signature made Fri 26 Jun 2020 14:42:17 BST
# gpg: using RSA key F13338574B662389866C7682BFFBD25F78C7AE83
# gpg: issuer "pbonzini@redhat.com"
# gpg: Good signature from "Paolo Bonzini <bonzini@gnu.org>" [full]
# gpg: aka "Paolo Bonzini <pbonzini@redhat.com>" [full]
# Primary key fingerprint: 46F5 9FBD 57D6 12E7 BFD4 E2F7 7E15 100C CD36 69B1
# Subkey fingerprint: F133 3857 4B66 2389 866C 7682 BFFB D25F 78C7 AE83

* remotes/bonzini/tags/for-upstream: (31 commits)
i386: Mask SVM features if nested SVM is disabled
ibex_uart: fix XOR-as-pow
vmport: move compat properties to hw_compat_5_0
hyperv: vmbus: Remove the 2nd IRQ
kvm: i386: allow TSC to differ by NTP correction bounds without TSC scaling
numa: forbid '-numa node, mem' for 5.1 and newer machine types
osdep: Make MIN/MAX evaluate arguments only once
target/i386: Add notes for versioned CPU models
target/i386: reimplement fpatan using floatx80 operations
target/i386: reimplement fyl2x using floatx80 operations
target/i386: reimplement fyl2xp1 using floatx80 operations
target/i386: reimplement fprem, fprem1 using floatx80 operations
softfloat: return low bits of quotient from floatx80_modrem
softfloat: do not set denominator high bit for floatx80 remainder
softfloat: do not return pseudo-denormal from floatx80 remainder
softfloat: fix floatx80 remainder pseudo-denormal check for zero
softfloat: merge floatx80_mod and floatx80_rem
target/i386: reimplement f2xm1 using floatx80 operations
xen: Actually fix build without passthrough
Makefile: Install qemu-[qmp/ga]-ref.* into the directory "interop"
...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

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# 5eebc49d 17-Jun-2020 Joseph Myers <joseph@codesourcery.com>

target/i386: reimplement fyl2xp1 using floatx80 operations

The x87 fyl2xp1 emulation is currently based around conversion to
double. This is inherently unsuitable for a good emulation of any
floatx

target/i386: reimplement fyl2xp1 using floatx80 operations

The x87 fyl2xp1 emulation is currently based around conversion to
double. This is inherently unsuitable for a good emulation of any
floatx80 operation, even before considering that it is a particularly
naive implementation using double (adding 1 then using log rather than
attempting a better emulation using log1p).

Reimplement using the soft-float operations, as was done for f2xm1; as
in that case, m68k has related operations but not exactly this one and
it seemed safest to implement directly rather than reusing the m68k
code to avoid accumulation of errors.

A test is included with many randomly generated inputs. The
assumption of the test is that the result in round-to-nearest mode
should always be one of the two closest floating-point numbers to the
mathematical value of y * log2(x + 1); the implementation aims to do
somewhat better than that (about 70 correct bits before rounding). I
haven't investigated how accurate hardware is.

Intel manuals describe a narrower range of valid arguments to this
instruction than AMD manuals. The implementation accepts the wider
range (it's needed anyway for the core code to be reusable in a
subsequent patch reimplementing fyl2x), but the test only has inputs
in the narrower range so that it's valid on hardware that may reject
or produce poor results for inputs outside that range.

Code in the previous implementation that sets C2 for some out-of-range
arguments is not carried forward to the new implementation; C2 is
undefined for this instruction and I suspect that code was just
cut-and-pasted from the trigonometric instructions (fcos, fptan, fsin,
fsincos) where C2 *is* defined to be set for out-of-range arguments.

Signed-off-by: Joseph Myers <joseph@codesourcery.com>

Message-Id: <alpine.DEB.2.21.2006172320190.20587@digraph.polyomino.org.uk>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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