JIT: do early block merging in more cases #86157
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OSR and PGO both rely on the fact that the early flowgraph the JIT builds is the same flowgraph as the one seen in a previous JIT complation of that method, since there is metadata (patchpoint offset, pgo schema) that refers to the flowgraph. Previous work here (dotnet#85860) didn't ensure this for enough cases. In particular if Tier0 does not do early block merging, but OSR does, it's possible for the OSR entry point to fall within a merged block range, which the JIT is not prepared to handle. This lead to the asserts seen in dotnet#86125. The fix is to enable early block merging unless we're truly in a minopts or debug codegen mode (previous to this Tier0 would not merge unless it also was instrumenting; now it will always merge). An alternative fix would be to find the block containing the OSR entry IL offset, scan its statements, and split the block at the right spot, but that seemed more involved. Fixes dotnet#86125.
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch Issue DetailsOSR and PGO both rely on the fact that the early flowgraph the JIT builds is the same flowgraph as the one seen in a previous JIT complation of that method, since there is metadata (patchpoint offset, pgo schema) that refers to the flowgraph. Previous work here (#85860) didn't ensure this for enough cases. In particular if Tier0 does not do early block merging, but OSR does, it's possible for the OSR entry point to fall within a merged block range, which the JIT is not prepared to handle. This lead to the asserts seen in #86125. The fix is to enable early block merging unless we're truly in a minopts or debug codegen mode (previous to this Tier0 would not merge unless it also was instrumenting; now it will always merge). An alternative fix would be to find the block containing the OSR entry IL offset, scan its statements, and split the block at the right spot, but that seemed more involved. Fixes #86125.
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@EgorBo PTAL Some diffs in Tier0 codegen. |
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/azp run runtime-jit-experimental |
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Azure Pipelines successfully started running 1 pipeline(s). |
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Will fix formatting after the experimental leg completes. |
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Experimental had what looks like two unrelated failures in jit-stress-splitting. Will ignore for now as the OSR failures are fixed. |
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Replay failures are related to collections issues. |
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OSR and PGO both rely on the fact that the early flowgraph the JIT builds is the same flowgraph as the one seen in a previous JIT complation of that method, since there is metadata (patchpoint offset, pgo schema) that refers to the flowgraph. Previous work here (#85860) didn't ensure this for enough cases.
In particular if Tier0 does not do early block merging, but OSR does, it's possible for the OSR entry point to fall within a merged block range, which the JIT is not prepared to handle. This lead to the asserts seen in #86125.
The fix is to enable early block merging unless we're truly in a minopts or debug codegen mode (previous to this Tier0 would not merge unless it also was instrumenting; now it will always merge).
An alternative fix would be to find the block containing the OSR entry IL offset, scan its statements, and split the block at the right spot, but that seemed more involved.
Fixes #86125.