[mono][swift-interop] Support for Swift struct lowering in callback returns #104949
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6 tasks
This was referenced Jul 16, 2024
matouskozak
requested review from
BrzVlad,
kotlarmilos,
fanyang-mono and
jkurdek
This was referenced Jul 16, 2024
Open
lambdageek
reviewed
Jul 17, 2024
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This was referenced Jul 17, 2024
Build failure: Static graph-based restore failed with exit code .* but did not log an error.
#103526
Open
jkurdek
approved these changes
Jul 18, 2024
| @@ -988,7 +988,8 @@ get_call_info (MonoMemPool *mp, MonoMethodSignature *sig) | |||
| /* | |||
| * We need to set this even when sig->pinvoke is FALSE, because the `cinfo` gets copied to the | |||
| * `cfg->arch` on the first pass. However, later in `amd64_handle_swift_return_buffer_reg` we | |||
| * condition the Swift return buffer handling only to P/Invoke calls. | |||
| * condition the Swift return buffer handling only to P/Invoke calls. This however can trigger | |||
| * a false positive in some scenarios where the Swift return buffer is not needed. | |||
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What are those false positive triggering scenarios?
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Mostly cases where struct is large enough that it would normally (outside swiftcall) be returned by a reference but small enough that during swiftcall it is returned via registers.
Co-authored-by: Jeremi Kurdek <[email protected]>
kotlarmilos
approved these changes
Jul 18, 2024
| @@ -2368,6 +2400,9 @@ mono_arch_get_llvm_call_info (MonoCompile *cfg, MonoMethodSignature *sig) | |||
| linfo->ret.storage = LLVMArgVtypeRetAddr; | |||
| linfo->vret_arg_index = cinfo->vret_arg_index; | |||
| break; | |||
| case ArgSwiftValuetypeLoweredRet: | |||
| linfo->ret.storage = LLVMArgNone; // LLVM compilation of pinvoke wrappers is not supported, see emit_method_inner in mini-llvm.c | |||
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No, we can't assert here. See #104949 (comment).
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Description
This PR adds support in Mono runtime for Swift
@frozenstruct lowering in function returns in reverse P/Invoke scenario. These changes are a follow-up to #104389 which introduced support for direct P/Invoke scenario and contains detailed description of the problem.Implementation
The key implementation part was done in #104389. Same as in direct P/Invokes, the struct can be returned as a lowered sequence of primitives or by reference.
Returned by lowered sequence:
mono_arch_emit_epilogwhere the lowered sequence of primitives is stored into dedicated return registers.Returned by reference:
ArgVtypeByRefwith no extra changes.ArgValuetypeAddrInIRegwith specific handling where we need to load the return buffer address passed by Swift caller fromRAXreg. intovret_addrinside themono_arch_emit_prologVerification
The changes are verified using the Interop/Swift/SwiftCallbackAbiStress runtime tests. The extended set of 2500 test cases was used locally to further verify the lowering support. The fullAOT functionality was only verified in local settings due to missing coverage on CI.
Contributes to #102077