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-boun...@openjdk.java.net [mailto:mlvm-dev-boun...@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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