forked from OSchip/llvm-project
3cbbded68c
For each natural loop with multiple exit blocks, this pass creates a new block N such that all exiting blocks now branch to N, and then control flow is redistributed to all the original exit blocks. The bulk of the tranformation is a new function introduced in BasicBlockUtils that an redirect control flow from a set of incoming blocks to a set of outgoing blocks via a common "hub". This is a useful workaround for a limitation in the structurizer which incorrectly orders blocks when processing a nest of loops. This pass bypasses that issue by ensuring that each natural loop is recognized as a separate region. Since the structurizer is a region pass, it no longer sees a nest of loops in a single region, and instead processes each "level" in the nesting as a separate region. The AMDGPU backend provides a new option to enable this pass before the structurizer, which may eventually be enabled by default. Reviewers: madhur13490, arsenm, nhaehnle Reviewed By: nhaehnle Differential Revision: https://reviews.llvm.org/D75865 |
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| llc.cpp | ||