RFR (S) 8131682: C1 should use multibyte nops everywhere (original) (raw)

Aleksey Shipilev aleksey.shipilev at oracle.com
Fri Jul 17 13:29:32 UTC 2015

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Hi there,

C1 is not very good at inlining and intrisifying methods, and hence the call performance is important there. One nit that we can see in the generated code on x86 is that C1 uses the single-byte nops, even for long nop strides.

This improvement fixes that: https://bugs.openjdk.java.net/browse/JDK-8131682 http://cr.openjdk.java.net/~shade/8131682/webrev.00/

Testing:

• JPRT -testset hotspot on open platforms
• eyeballing the generated assembly with -XX:TieredStopAtLevel=1

(I understand the symmetric change is going to be needed in closed parts, but let's polish the open part first).

Thanks, -Aleksey

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