llvm / llvm/llvm-project

Use BFI as the value that should be conserved in SimpleLoopUnswitch

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loopoptim
Dominant language
LLVM
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Description

In `buildPartialUnswitchConditionalBranch`, we could use the BFI of BBs in the loop to estimate the branch weights of the unswitched branch.

Contributor guide

Open the contributing guide

Research direction

Locate buildPartialUnswitchConditionalBranch and trace how SimpleLoopUnswitch currently estimates branch weights. Read the surrounding loop-unswitch implementation and its BFI usage; done means the unswitched branch weights use BFI information for the loop blocks as described.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp
Domain
compilers
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
35/100

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