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f3f13a2637
This change enables the `--gc-sections` linker flag for WebAssembly
targets by default. This flag has been disabled because it did not
respect `llvm.used` and it caused stripping `swift5` metadata sections
even though they were used through encapsulation symbols (a.k.a `__start`/`__stop`).
The issue has been fixed in the LLVM side (ba3c1f9ce3)
by adding new segment flags to the WebAssembly object file format.
111 lines
4.0 KiB
C++
111 lines
4.0 KiB
C++
//===--- SwiftRT-ELF-WASM.cpp ---------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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#include "ImageInspectionCommon.h"
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#include "swift/shims/MetadataSections.h"
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#include "swift/Runtime/Backtrace.h"
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#include <cstddef>
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#include <new>
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#if defined(__ELF__)
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extern "C" const char __dso_handle[];
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#elif defined(__wasm__)
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// NOTE: Multi images in a single process is not yet
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// stabilized in WebAssembly toolchain outside of Emscripten.
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static constexpr const void *__dso_handle = nullptr;
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#endif
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#if SWIFT_ENABLE_BACKTRACING
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// Drag in a symbol from the backtracer, to force the static linker to include
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// the code.
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static const void *__backtraceRef __attribute__((used))
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= (const void *)swift::runtime::backtrace::_swift_backtrace_isThunkFunction;
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#endif
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// Create empty sections to ensure that the start/stop symbols are synthesized
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// by the linker. Otherwise, we may end up with undefined symbol references as
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// the linker table section was never constructed.
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#if defined(__ELF__)
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# define DECLARE_EMPTY_METADATA_SECTION(name) __asm__("\t.section " #name ",\"a\"\n");
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#elif defined(__wasm__)
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# define DECLARE_EMPTY_METADATA_SECTION(name) __asm__("\t.section " #name ",\"R\",@\n");
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#endif
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#define DECLARE_SWIFT_SECTION(name) \
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DECLARE_EMPTY_METADATA_SECTION(name) \
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__attribute__((__visibility__("hidden"),__aligned__(1))) extern const char __start_##name; \
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__attribute__((__visibility__("hidden"),__aligned__(1))) extern const char __stop_##name;
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extern "C" {
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DECLARE_SWIFT_SECTION(swift5_protocols)
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DECLARE_SWIFT_SECTION(swift5_protocol_conformances)
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DECLARE_SWIFT_SECTION(swift5_type_metadata)
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DECLARE_SWIFT_SECTION(swift5_typeref)
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DECLARE_SWIFT_SECTION(swift5_reflstr)
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DECLARE_SWIFT_SECTION(swift5_fieldmd)
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DECLARE_SWIFT_SECTION(swift5_assocty)
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DECLARE_SWIFT_SECTION(swift5_replace)
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DECLARE_SWIFT_SECTION(swift5_replac2)
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DECLARE_SWIFT_SECTION(swift5_builtin)
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DECLARE_SWIFT_SECTION(swift5_capture)
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DECLARE_SWIFT_SECTION(swift5_mpenum)
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DECLARE_SWIFT_SECTION(swift5_accessible_functions)
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DECLARE_SWIFT_SECTION(swift5_accessible_protocol_requirement_functions)
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DECLARE_SWIFT_SECTION(swift5_runtime_attributes)
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DECLARE_SWIFT_SECTION(swift5_tests)
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}
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#undef DECLARE_SWIFT_SECTION
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namespace {
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static swift::MetadataSections sections{};
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}
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__attribute__((__constructor__))
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static void swift_image_constructor() {
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#define SWIFT_SECTION_RANGE(name) \
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{ reinterpret_cast<uintptr_t>(&__start_##name), \
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static_cast<uintptr_t>(&__stop_##name - &__start_##name) }
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::new (§ions) swift::MetadataSections {
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swift::CurrentSectionMetadataVersion,
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{ __dso_handle },
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nullptr,
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nullptr,
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SWIFT_SECTION_RANGE(swift5_protocols),
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SWIFT_SECTION_RANGE(swift5_protocol_conformances),
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SWIFT_SECTION_RANGE(swift5_type_metadata),
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SWIFT_SECTION_RANGE(swift5_typeref),
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SWIFT_SECTION_RANGE(swift5_reflstr),
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SWIFT_SECTION_RANGE(swift5_fieldmd),
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SWIFT_SECTION_RANGE(swift5_assocty),
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SWIFT_SECTION_RANGE(swift5_replace),
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SWIFT_SECTION_RANGE(swift5_replac2),
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SWIFT_SECTION_RANGE(swift5_builtin),
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SWIFT_SECTION_RANGE(swift5_capture),
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SWIFT_SECTION_RANGE(swift5_mpenum),
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SWIFT_SECTION_RANGE(swift5_accessible_functions),
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SWIFT_SECTION_RANGE(swift5_accessible_protocol_requirement_functions),
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SWIFT_SECTION_RANGE(swift5_runtime_attributes),
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SWIFT_SECTION_RANGE(swift5_tests),
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};
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#undef SWIFT_SECTION_RANGE
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swift_addNewDSOImage(§ions);
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}
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