[Qemu-devel] [PATCH] Fix guest x86/amd64 helper_fprem/helper_fprem1

[Julian Seward]

The helpers for x86/amd64 fprem and fprem1 in target-i386/helper.c are
significantly borked and, for example, cause konqueror in RedHat8 (x86
guest) to go into an infinite loop when displaying http://news.bbc.co.uk.

helper_fprem has the following borkage:
- various Inf/Nan/zero inputs not handled correctly
- incorrect rounding when converting negative 'dblq' to 'q'
- incorrect order of assignment to C bits (0,3,1 not 0,1,3)

helper_fprem1 has those problems and is also incorrect about the points
at which its rounding needs to differ from that of helper_fprem.

Patch below fixes all these.  It brings the fprem and fprem1 behaviour 
very much closer to the hardware -- not identical, but close.  Some
+0.0 results should really be -0.0 and there may still be other differences.

Anyway konquerer no longer loops with the patch applied.

J

x86_fprem.diff
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