[ros-dev] [ros-diffs] [dgorbachev] 53907: [NTOSKRNL] Use inline asm in KiIsNpxErrataPresent(). C code can be optimized in a wrong way.

Dmitry Gorbachev d.g.gorbachev at gmail.com
Sat Oct 1 16:38:36 UTC 2011


It is not a compiler fault. The compiler does here two legitimate things:

1) Math can be moved outside _disable/_enable/__writecr0. It can be
fixed by making other local vars volatile.

2) Some time ago, you suggested to look into building with -Ofast
option. So I went agead and compiled with it. GCC replaces division by
multiplication, which causes some loss of precision; thus, the test
fails. This, however, works:

  ErrataPresent = (Value1 / Value2 * 3145727.0) != 4195835.0;

> I hate these kinds of patches.

I do not see a reason for grievance. This handwritten piece is shorter
than compiler-generated code, it is only for i386, there is no need to
port it to arm and amd64, not speaking already that it's just for
"some completely obsolete bs".



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