Florian Hahn 4495a6b141 [BreakCritEdges] Add option to opt-out of perserving loop-simplify. ...

This patch adds a new option to CriticalEdgeSplittingOptions to control
whether loop-simplify form must be preserved. It is them used by GVN to
indicate that loop-simplify form does not have to be preserved.

This fixes a crash exposed by 189efe295b.

If the critical edge we are splitting goes from a block inside a loop to
a block outside the loop, splitting the edge will create a new exit
block. As a result, the new block will branch to the original exit
block, which will add a non-loop predecessor, breaking loop-simplify
form. To preserve loop-simplify form, the predecessor blocks of the
original exit are split, but that does not work for blocks with
indirectbr terminators. If preserving loop-simplify form is requested,
bail out , before making any changes.

Reviewers: reames, hfinkel, davide, efriedma

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D81582

2020-06-12 11:47:13 +01:00

100 KiB

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