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Utilize VN-based non-null knowledge better #69808

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SingleAccretion
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@SingleAccretion SingleAccretion commented May 25, 2022

Previously, global non-null assertion propagation would give up on any non-ADD(LCL_VAR, CONST)-like trees. This is correct for actual assertion-based propagation (since we record assertions based on conservative VNs and those propagate only through locals), but is unnecessarily conservative when it comes to utilizing non-nullness provided by VN.

Fix this by moving the IR checks after the VN check.

Diffs.

@dotnet-issue-labeler dotnet-issue-labeler bot added the area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI label May 25, 2022
@ghost ghost added the community-contribution Indicates that the PR has been added by a community member label May 25, 2022
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ghost commented May 25, 2022

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Issue Details

Previously, global non-null assertion propagation would give up on any non-ADD(LCL_VAR, CONST)-like trees. This is correct for actual assertion-based propagation (since we record assertions based on conservative VNs and those propagate only through locals), but is unnecessarily conservative when it comes to utilizing non-nullness provided by VN.

Fix this by moving the IR checks after the VN check.

We are expecting a moderate amount of positive diffs.

Author: SingleAccretion
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area-CodeGen-coreclr, community-contribution

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@SingleAccretion SingleAccretion force-pushed the More-Non-Null-AssertionProp branch from b535337 to b874a31 Compare May 25, 2022 18:12
@SingleAccretion SingleAccretion marked this pull request as ready for review May 25, 2022 20:55
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SingleAccretion commented May 25, 2022

Libraries Test Run checked coreclr Linux_musl arm Release failure is #60705

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Previously, global non-null assertion propagation would give up
on any non-"ADD(LCL_VAR, CONST)"-like trees. This is correct for
actual assertion-based propagation (since we record assertions
based on conservative VNs and those propagate only through locals),
but is unnecessarily conservative when it comes to utilizing
non-nullness provided by VN.

Fix this by moving the IR checks after the VN check.
@jakobbotsch jakobbotsch merged commit 684fc2d into dotnet:main Jun 4, 2022
@SingleAccretion SingleAccretion deleted the More-Non-Null-AssertionProp branch June 4, 2022 09:50
@ghost ghost locked as resolved and limited conversation to collaborators Jul 4, 2022
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