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.NET is a cross-platform runtime for cloud, mobile, desktop, and IoT apps.
https://docs.microsoft.com/dotnet/core/
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Investigate the heuristics for creating DummyDef in LSRA #71539

Open kunalspathak opened 2 years ago

kunalspathak commented 2 years ago

Today, if there is a CSE candidate has definition in the middle of deeply nested loop, we end up adding DummyDef refpositions in blocks that doesn't have its uses and that leads to spilling/reloading such variables without need. This happens because of the way we choose the predecessor of such blocks and we should revisit to see if we can also accommodate the variable location where it is defined instead of just checking the block's flow. Relevant discussion in https://github.com/dotnet/runtime/pull/70271#issuecomment-1167949183

category:design theme:register-allocator skill-level:expert cost:small impact:medium

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Issue Details
Today, if there is a CSE candidate has definition in the middle of deeply nested loop, we end up adding `DummyDef` refpositions in blocks that doesn't have its uses and that leads to spilling/reloading such variables without need. This happens because of the way we choose the predecessor of such blocks and we should revisit to see if we can also accommodate the variable location where it is defined instead of just checking the block's flow. Relevant discussion in https://github.com/dotnet/runtime/pull/70271#issuecomment-1167949183
Author: kunalspathak
Assignees: kunalspathak
Labels: `area-CodeGen-coreclr`
Milestone: 8.0.0