[Bug 250454] PT_GETFPREGS on i386 oversimplifies translating FPU Tag Word

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=250454

--- Comment #4 from commit-hook at FreeBSD.org ---
A commit references this bug:

Author: kib
Date: Wed Oct 21 00:15:13 UTC 2020
New revision: 366904
URL: https://svnweb.freebsd.org/changeset/base/366904

Log:
  Improve FPU Tag Word reconstruction on i386 to indicate register states.

  Improve the code reconstructing en_tw in struct fpreg32 from FXSAVE
  results so that all register states are indicated correctly.  The
  previous code unconditionally mapped non-empty register state to
  'normalized value' constant.  The new code explicitly distinguishes
  the 'zero value' and 'special value' constants as well.  This improves
  consistency between real FSAVE and translation from FXSAVE, and
  ensures that tests using PT_GETFPREGS can rely on a single correct
  value independently of the underlying implementation.

  PR:   250454
  Sponsored by: The FreeBSD Foundation
  Obtained from:        Moritz Systems
  Submitted by: Micha? G?rny <mgorny at moritz.systems>
  Discussed with:       emaste
  MFC after:    1 week
  Differential revision:        https://reviews.freebsd.org/D26856

Changes:
  head/sys/amd64/ia32/ia32_reg.c
  head/sys/i386/i386/npx.c

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