[jdk17] RFR: 8269879: [PPC64] C2: Math.rint intrinsic uses wrong rounding mode

[Martin Doerr]

On Mon, 5 Jul 2021 20:42:59 GMT, Lutz Schmidt <lucy at openjdk.org> wrote:

> The changes look good so far.

Thanks!

> You are mentioning that the now used instruction is available from Power7 and that for older versions of the Power spec, the intrinsic should be disabled. I am missing such a change, probably in vm_version_ppc.cpp.

See change in Matcher::match_rule_supported(int opcode).

> Furthermore, you mention that the instruction needs a special (non-default) setting of the rounding mode control flags. How can such flag setting be assured?

No, it's the default setting (see referenced ABI chapters).

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PR: https://git.openjdk.java.net/jdk17/pull/215