[cherry-pick][SelectionDAG] Disable FastISel for swiftasync functions (#70741) #7787
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Most (x86) swiftasync functions tend to use both SelectionDAGISel and FastISel lowering: * FastISel argument lowering can only handle C calling convention. * FastISel fails mid-BB in a number of ways, including in simple `ret void` instructions under certain circumstances. This dance of SelectionDAG (argument) -> FastISel (some instructions) -> SelectionDAG(remaining instructions) is lossy; in particular, Argument information lowering is cleared after that first SelectionDAG run. Since swiftasync functions rely heavily on proper Argument lowering for debug information, this patch disables the use of FastISel in such functions. (cherry picked from commit 83729e6)
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@swift-ci please test |
felipepiovezan
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to felipepiovezan/swift
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Nov 14, 2023
With swiftlang/llvm-project#7787 merged, we can now finally renable these tests, as the x86 swift async handling should be properly preserved by the x86 instruction selector. These tests contained some incorrect checks from a time where it was expecting an entry value even in the entry funclet of coroutines. For example, it had this: ``` CHECK-NEXT: [[ASYNC_REG:DW_OP_.*], DW_OP_plus_uconst 0x10, DW_OP_plus_uconst 0x8, DW_OP_deref ``` Which tries to find some "async reg", but really matches anything. It worked by accident on arm, but not on x86. The correct check is simply: ``` CHECK-NOT: OP_entry_value ```
adrian-prantl
approved these changes
Nov 14, 2023
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Most (x86) swiftasync functions tend to use both SelectionDAGISel and FastISel lowering:
ret voidinstructions under certain circumstances.This dance of SelectionDAG (argument) -> FastISel (some instructions) -> SelectionDAG(remaining instructions) is lossy; in particular, Argument information lowering is cleared after that first SelectionDAG run.
Since swiftasync functions rely heavily on proper Argument lowering for debug information, this patch disables the use of FastISel in such functions.
(cherry picked from commit 83729e6)