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llvm-mirror/tools/llc
Sameer Sahasrabuddhe b4d5045713 Introduce unify-loop-exits pass.
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
2020-03-30 13:23:56 -04:00
..
CMakeLists.txt Don't export symbols from clang/opt/llc if plugins are disabled. 2020-03-23 12:17:09 -07:00
llc.cpp Introduce unify-loop-exits pass. 2020-03-30 13:23:56 -04:00
LLVMBuild.txt