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AMDGPU/SI: Handle infinite loop for the structurizer to work with CFG with…

Authored by cfang on May 17 2018, 9:45 AM.

Description

AMDGPU/SI: Handle infinite loop for the structurizer to work with CFG with infinite loops.

Summary:

The current StructurizeCFG pass only works for CFG with one exit. AMDGPUUnifyDivergentExitNodes combines multiple "return" blocks and/or "unreachable" blocks

to one exit block for the Structurizer to work. However, infinite loop is another kind of special "exit", and if we don't handle it, the case of multiple exits will prevent the structurizer from working.

In this work, for each infinite loop, we add a dummy edge to the "return" block, and thus the AMDGPUUnifyDivergentExitNodes pass will work with infinite loops.
This will make CFG with infinite loops be structurized.

Reviewer:

nhaehnle

Differential Revision:

https://reviews.llvm.org/D46340

llvm-svn: 332625