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JIT: handle interaction of OSR, PGO, and tail calls #62263

Merged
merged 3 commits into from Dec 2, 2021
Merged

JIT: handle interaction of OSR, PGO, and tail calls #62263

merged 3 commits into from Dec 2, 2021

Commits on Dec 2, 2021

  1. JIT: handle interaction of OSR, PGO, and tail calls 

    When both OSR and PGO are enabled, the jit will add PGO probes to OSR methods.
And if the OSR method also has a tail call, the jit must take care to not add
block probes to any return block reachable from possible tail call blocks.

Instead, instrumentation should create copies of the return block probe in each
return block predecessor (possibly splitting critical edges to make this viable).

Because all this happens early on, there are no pred lists. The analysis leverages
cheap preds instead, which means it needs to handle cases where a given pred has
multiple pred list entries. And it must also be aware that the OSR method's actual
flowgraph is a subgraph of the full initial graph.

This came up while scouting what it would take to enable OSR by default.
See dotnet#61934.
    @AndyAyersMS
    AndyAyersMS committed Dec 2, 2021
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  2. Be careful not to have multiple pred list entries referring to the in… 

    …termedary.
    @AndyAyersMS
    AndyAyersMS committed Dec 2, 2021
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  3. review feedback

    @AndyAyersMS
    AndyAyersMS committed Dec 2, 2021
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