Hotspot loves PHP.reboot

[MacGregor, Duncan (GE Energy)]

Could we do pass a method handle into this hypothetical to this
hypothetical addDetectingOverflow and allow thus allow the caller to
specify what should happen in the overflow case? Or does that still
leave too much of a problem regarding actually returning the values?

 

From: mlvm-dev-bounces at openjdk.java.net
[mailto:mlvm-dev-bounces at openjdk.java.net] On Behalf Of John Rose
Sent: 06 September 2011 21:05
To: Da Vinci Machine Project
Subject: Re: Hotspot loves PHP.reboot

 

On Sep 6, 2011, at 8:51 AM, Charles Oliver Nutter wrote:





Did we ever figure out if it's possible to trick Hotspot into doing a
JO instead of the raw bit-level operations? John/Christian/Tom: what
would it take to get HS to "know" that we're doing an integer
overflow-after-maths check and do the (faster?) JO?



 

(1) Write a compelling API for something like
Integer.addDetectingOverflow.

(2) Roll it into JDK 8+epsilon.

(3) Do the JIT work.

 

People have thought on and off about (1) for many years, but with no
clear winner.  Exceptions or boxed objects have unpleasant interactions
and are hard to use, while smuggling out the 33rd bit some other way
(TLS, a long or double, a return-by-reference, a sentinel value) is
painful.

 

(This is a case where tuples would make things simple, but it is not
enough to motivate introducing tuples.)

 

-- John

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