Integrated: 8278296: Generalize long range check transformation

[Roland Westrelin]

On Fri, 7 Jan 2022 15:18:04 GMT, Roland Westrelin <roland at openjdk.org> wrote:

> 8259609 (C2: optimize long range checks in long counted loops) only
> covered the case of a counted loop with a positive stride and a range
> check with a positive scale. This change generalizes the long range
> check transformation to all 4 combinations of stride and scale signs.
> 
> The stride > 0, scale > 0 case (covered 8259609) was tweaked so it now
> uses Qmax computed as the inclusive limit of j*K+Q. That helps in
> generalizing the formulas to other cases.
> 
> The addition of PhaseIdealLoop::is_scaled_iv_plus_extra_offset() was
> required for the case of negative scale in an int loop. The range
> check then has the shape:
> 
> (CmpUL (AddL (ConvI2L (SubI ConI (LshiftI (Phi
> 
> with ConI, the zero constant.
> 
> This change also addresses this comment from John:
> 
> https://github.com/openjdk/jdk/pull/6576#discussion_r765343664
> 
> as part of 8276116 (C2: optimize long range checks in int counted loops)

This pull request has now been integrated.

Changeset: ef266d77
Author:    Roland Westrelin <roland at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/ef266d77b6eb54d7e30a0aafd8a3e8c8f4f0e43a
Stats:     723 lines in 7 files changed: 489 ins; 79 del; 155 mod

8278296: Generalize long range check transformation

Reviewed-by: jrose, thartmann

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PR: https://git.openjdk.java.net/jdk/pull/6989