RFR: 8240615: is_power_of_2() has Undefined Behaviour and is inconsistent

[Andrew Haley]

On 3/10/20 6:06 PM, Vladimir Kozlov wrote:
> Why you did not cast constant to (julong) in btrL_mem_imm() x86_64.ad?

I don't think that it's necessary. (~$con$$constant) returns a jlong
which gets passed to log2_long(julong x), so it gets converted to
from julong to julong at the point of the call.

> I looked through C1 and C2 code usage of is_power_of_2(). And it is not clear to me if we handle MAX and MIN values 
> correctly in some cases (mulnode.cpp, divnode.cpp). But it is a different issue.
> 
> I think your is_power_of_2() change should be fine for C2 and C1 code.

OK, thanks.

-- 
Andrew Haley  (he/him)
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
https://keybase.io/andrewhaley
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