[CSE] Stack nest at OSSA lowering after inlining. #64005
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CSE inlines a portion of lazy property getters. Now that in OSSA `partial_apply [on_stack]`s are represented as owned values rather than stack locations, it is possible for their destroys to violate stack discipline. A direct lowering of the instructions to non-OSSA would violate stack nesting. Previously, when inlining during CSE, it was assumed that the callee maintained stack discipline. And, when inlining an OSSA function into a non-OSSA function, OSSA instructions were lowered directly. The result was that stack discipline could be violated when directly lowering callees with `partial_apply [on_stack]`s that violate stack discipline upon direct lowering. Here, when CSE inlining a lazy property getter in OSSA form into a function lowered out of OSSA form, stack nesting is fixed up.
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@swift-ci please test |
atrick
reviewed
Mar 3, 2023
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@nate-chandler looks great to me too.
Just an observation. It might be less bug prone for the inliner to do this work itself. For efficiency, we might then want fixNesting to work on a region rather than the whole function.
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CSE inlines a portion of lazy property getters.
Now that in OSSA
partial_apply [on_stack]s are represented as owned values rather than stack locations, it is possible for their destroys to violate stack discipline. A direct lowering of the instructions to non-OSSA would violate stack nesting.Previously, when inlining during CSE, it was assumed that the callee maintained stack discipline. And, when inlining an OSSA function into a non-OSSA function, OSSA instructions were lowered directly. The result was that stack discipline could be violated when directly lowering callees with
partial_apply [on_stack]s that violate stack discipline upon direct lowering.Here, when CSE inlining a lazy property getter in OSSA form into a function lowered out of OSSA form, stack nesting is fixed up.