RFR(M): 8027754: Enable loop optimizations for loops with MathExact inside (original) (raw)

Rickard Bäckman rickard.backman at oracle.com
Thu Jan 23 03:27:23 PST 2014

Hi all,

this change is going to 9 (and backporting to 8u20). Can I please have this change reviewed?

The implementation of different j.l.Math.mathExact() didn't work very well with different optimizations because there was one node that generated both control and data. This change has a new implementation where each call to j.l.Math.mathExact() generates a Overflow node and a normal math operation node (in the integer add example: OverflowAddINode and a AddINode). The Overflow node is responsible for generating control.

In the end we generate assembly like:

mov rdx, rdi add rdx, rsi ... mov rax, rdi add rax, rsi jo

With one add instruction for the data and one for flags. Future improvements could be to try to match the Overflow and the math operation and remove one of them.

Bug: https://bugs.openjdk.java.net/browse/JDK-8027754 Webrev: http://cr.openjdk.java.net/~rbackman/8027754/

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