[aarch64-port-dev ] RFR: 8193266: AArch64: TestOptionsWithRanges.java SIGSEGV

Andrew Haley aph at redhat.com
Sat Dec 9 19:02:19 UTC 2017

On 09/12/17 11:37, Andrew Haley wrote:
> Hmm.  This sort-of papers over the problem, in that it disables XOR-
> encoding of class metadata.  I would have thought it makes more sense
> to set narrow_klass_base high enough so that this does not happen.  We
> really want narrow_klass_shift to be zero if we can, which should be
> OK if the shared klasses are in a 4G range.

And I now see that in the very odd code in question the shift is set
to 3, regardless of the fact that it's not necessary.  Something to
do with AOT, which I guess always does the shift.  I'd prefer
AArch64 always to set the shift to zero, and we could then search
for a suitable base.  We never need a shift for compressed classes,
given that 4G seems to be hard-wired as a maximum size.

We could establish the convention that the shift is always zero
on AArch64, and then this problem would go away completely.

Andrew Haley
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
EAC8 43EB D3EF DB98 CC77 2FAD A5CD 6035 332F A671

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