Integrated: 8254317: C2: Resource consumption of ConvI2LNode::Ideal() grows exponentially

[Roberto Castañeda Lozano]

On Mon, 19 Oct 2020 08:36:53 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

> Prevent exponential number of calls to `ConvI2LNode::Ideal()` when AddIs are used multiple times by other AddIs in the optimization ConvI2L(AddI(x, y)) -> AddL(ConvI2L(x), ConvI2L(y)). This is achieved by (1) reusing existing ConvI2Ls if possible rather than eagerly creating new ones and (2) postponing the optimization of newly created ConvI2Ls. Remove hook node solution introduced in [8217359](https://github.com/openjdk/jdk/commit/cf554816d1952f722143e9d03ec669e80f955adf), since this is subsumed by (2). Use `phase->is_IterGVN()` rather than `can_reshape` to check if `ConvI2LNode::Ideal()` is called within iterative GVN, for clarity. Add regression tests that cover different shapes and sizes of AddI subgraphs, implicitly checking (by not timing out) that there is no combinatorial explosion.

This pull request has now been integrated.

Changeset: 432c387e
Author:    Roberto Castañeda Lozano <rcastanedalo at openjdk.org>
Committer: Tobias Hartmann <thartmann at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/432c387e
Stats:     190 lines in 2 files changed: 180 ins; 4 del; 6 mod

8254317: C2: Resource consumption of ConvI2LNode::Ideal() grows exponentially

Prevent exponential number of calls to ConvI2LNode::Ideal() when AddIs are used
multiple times by other AddIs in the optimization ConvI2L(AddI(x, y)) ->
AddL(ConvI2L(x), ConvI2L(y)). This is achieved by (1) reusing existing ConvI2Ls
if possible rather than eagerly creating new ones and (2) postponing the
optimization of newly created ConvI2Ls. Remove hook node solution introduced in
8217359, since this is subsumed by (2). Use phase->is_IterGVN() rather than
can_reshape to check if ConvI2LNode::Ideal() is called within iterative GVN, for
clarity. Add regression tests that cover different shapes and sizes of AddI
subgraphs, implicitly checking (by not timing out) that there is no
combinatorial explosion.

Co-authored-by: Vladimir Ivanov <vlivanov at openjdk.org>
Reviewed-by: vlivanov, kvn

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PR: https://git.openjdk.java.net/jdk/pull/727