RFR: C1 stores constants without read barriers

[Roman Kennke]

I thought that too. But then realized we don't need barriers on constants for store values. Will explain on IRC as soon as my internet conn is back alive...

Am 29. Juni 2017 13:55:31 MESZ schrieb Aleksey Shipilev <shade at redhat.com>:
>I think this part of C1 is incorrect when barriers are required for
>constants:
>http://cr.openjdk.java.net/~shade/shenandoah/c1-store-const-rb/webrev.01/
>
>This might explain a few test failures we have: the from-space constant
>is read
>before concurrent evacuation has the chance to update it. Then it gets
>stored to
>another heap location, and everything blows up.
>
>While we could conditionalize this on ShBarriersForConst, this is C1
>code, which
>does not have to be super-optimal. Surprisingly, the new code is what
>c1_LIRGenerator_aarch64 is already doing, so this patch seems good from
>the
>symmetry standpoint too.
>
>Testing: hotspot_gc_shenandoah
>
>Thanks,
>-Aleksey

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