[9] RFR(S): 8043284: Optimize signed integer comparison

[Vladimir Kozlov]

Hi Tobias,

You missed cop == Op_CmpI check.
And add checks for r0 and r1 != TypeInt::INT (no bottom type) in addition to != NULL.
You don't need t2 because there is already cmp2_type. Check cmp2_type for != TypeInt::INT too.
Use as_Sub() (which is cast) instead of isa_Sub() because there is is_Sub() check at the beginning already.

I don't see how second condition could happen because tr1 < tr2:

sub_tr1 == TypeInt::CC_GT && sub_tr2 == TypeInt::CC_LT

Instead of ConINode::make() you can use phase->intcon().

Thanks,
Vladimir

On 7/31/14 5:35 AM, Tobias Hartmann wrote:
> Hi,
>
> please review the following patch that fixes JDK-8043284.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8043284
> Webrev: http://cr.openjdk.java.net/~thartmann/8043284/webrev.00/
>
> == Problem ==
> Similar to the previous implementation of unsigned integer comparison (see JDK- 8042786), signed integer comparison does
> only consider the general integer range [MinInt, MaxInt] instead of two ranges when comparing the result of an
> overflowing AddI/SubI. However, there are situations where one can prove that both resulting ranges are unequal to the
> tested value (see 'TestIntegerComparison::testSigned' in the webrev). In this case the comparison can be optimized.
>
> == Solution ==
> Similar to the fix for JDK-8042786 we compute both type ranges if the add/sub overflows and compare them to the tested
> value. If we can prove that the value is always unequal, we replace the BoolNode by true or false (depending on the test).
> A jtreg test is added that triggers both the unsigned as well as the signed optimization.
>
> == Testing ==
> - Jtreg test (TestIntegerComparison)
> - JPRT
>
> Thanks,
> Tobias