[9] RFR (M) 8052081: Optimize generated by C2 code for Intel's Atom processor

Vladimir Kozlov vladimir.kozlov at oracle.com
Mon Aug 4 21:47:50 UTC 2014


Atom processor does not have AVX unit but it has SSE so we still can do 
vectorization. General changes in lcm.cpp and superword.cpp we done to 
improve vectorization.

CRC32 assembler code was modified to use only SSE instructions to 
execute it on Atom processors too.

Performance numbers show that we benefit from UseFPUForSpilling on 
general x86 cpus too. Its setting was moved from under AggressiveOpts. 
Note, we are regularly testing AggressiveOpts so this part of code was 
tested before.

OptoScheduling has negative effect on general x86 cpus so it is switched 
on only for Atom processor which benefits from it.

I did performance runs and JPRT testing (with UseAVX=0 and default).


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