[PATCH, RA]: Fix PR 39914: 96% performance regression in FP code with -O1

[Uros Bizjak]

Hello!

The fix for PR debug/39432 introduced big runtime regression for -O1 
compiled code. IMO, such a performance hit is not acceptable with -O1, 
we want to _optimize_ the code with -O. We have -O0 to achieve full 
debug functionality.

Attached patch reportedly fixes this regression.

2009-04-28  Uros Bizjak  <ubizjak@gmail.com>

    * ira-conflicts.c (ira_build_conflicts): Prohibit call used
    registers for allocnos created from user-defined variables only
    when not optimizing.

Patch was tested on x86_64-pc-linux-gnu. OK for mainline and 4.4.1 ?

Uros.
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