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With PE/COFF, one cannot reference a data symbol directly across the
binary module boundary. Instead, the reference must be indirected
through the Import Address Table (IAT) to allow for position
independence.
When generating a reference to a AsyncFunctionPointer ({i8*, i32}), we
tag the pointer as being indirected by tagging bit 1 (with the
assumption that native alignment will ensure 4/8 byte alignment, freeing
the bottom 2 bits at least for bit-packing). We tweak the
v-table/witness table emission such that all references to the
AsyncFunctionPointer are replaced with the linker synthetic import
symbol with the bit packing:
~~~
.quad __imp_$s1L1CC1yyYaKFTu+1
~~~
rather than
~~~
.quad $s1L1CC1yyYaKFTu
~~~
Upon access of the async function pointer reference, we open-code the
check for the following:
~~~
pointer = (pointer & 1) ? *(void **)(pointer & ~1) : pointer;
~~~
Thanks to @DougGregor for the discussion and the suggestion for the
pointer tagging. Thanks to @aschwaighofer for pointers to the code that
I had missed. Also, thanks to @SeanROlszewski for the original code
sample that led to the reduced test case.
Fixes: SR-15399
28 lines
590 B
Swift
28 lines
590 B
Swift
// RUN: %empty-directory(%t)
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// RUN: %target-build-swift-dylib(%t/%target-library-name(L)) -module-name L -emit-module -emit-module-path %t/L.swiftmodule %s -DL
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// RUN: %target-build-swift -I%t -L%t -lL -parse-as-library %s -module-name E -o %t/E %target-rpath(%t)
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// RUN: %target-codesign %t/E
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// RUN: %target-run %t/E %t/%target-library-name(L) | %FileCheck %s
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#if L
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open class C {
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public init() {}
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open func f() async {
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print("\(#function)")
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}
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}
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#else
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import L
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class D: C {
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}
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@main
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struct S {
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public static func main() async {
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await D().f()
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}
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}
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#endif
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// CHECK: f()
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