[PATCH][RFC] Fixing instability of -fschedule-insns for x86

[Igor Zamyatin <izamyatin at gmail dot com>]

Hi all!

Patch aims to fix instability introduced by first scheduler on x86. In
particular it targets following list:

[1] http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46843
[2] http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46829
[3] http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36680
[4] http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42295

Main idea of this activity is mostly to provide user a possibility to
safely turn on first scheduler for his codes. In some cases this could
positively affect performance, especially for in-order Atom.

It would be great to hear some feedback from the community about the change.

Thanks in advance,
Igor

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