Swift Runtime on WebAssembly (#11)

* [WASM] Build ImageInspectionShared even on macOS
ImageInspectionShared was built only if host OS is Linux. But it's
necessary when primary sdk is WASM.
* [WASM] Use llvm-ar instead of ranlib on macOS
Specify ar binary through extra-cmake-options
* [WASM] Install llvm through HomeBrew to use llvm-ar
* [WASM] Use llvm-ranlib instead of ranlib of Xcode
* [WASM] Read offset as pointer when target is wasm
Because WASM doesn't support relative pointer, compiler emit direct
address instead of offset from current address.
* [WASM] Copy SwiftRT-ELF.cpp into SwiftRT-WASM.cpp
* [WASM] Emit empty swift5 sections if there aren't
* [WASM] Remove swift_end and swift_start files

Author: kateinoigakukun

.github/workflows/main.yml

@@ -49,6 +49,8 @@ jobs:
             -DSWIFT_SDKS='WASM;LINUX' \
             -DSWIFT_BUILD_SOURCEKIT=FALSE \
             -DSWIFT_ENABLE_SOURCEKIT_TESTS=FALSE \
+            -DCMAKE_AR='$sourcedir/wasi-sdk/bin/llvm-ar' \
+            -DCMAKE_RANLIB='$sourcedir/wasi-sdk/bin/llvm-ranlib' \
           " \
           --build-stdlib-deployment-targets "wasm-wasm32" \
           --build-swift-static-stdlib \
@@ -73,7 +75,7 @@ jobs:
     - uses: actions/checkout@v1
     - name: Run a multi-line script
       run: |
-        brew install cmake ninja
+        brew install cmake ninja llvm
         ./utils/update-checkout --clone --scheme wasm
         git checkout $GITHUB_SHA
         export sourcedir=$PWD/..
@@ -96,6 +98,8 @@ jobs:
             -DSWIFT_OSX_x86_64_ICU_STATICLIB=TRUE \
             -DSWIFT_BUILD_SOURCEKIT=FALSE \
             -DSWIFT_ENABLE_SOURCEKIT_TESTS=FALSE \
+            -DCMAKE_AR='/usr/local/opt/llvm/bin/llvm-ar' \
+            -DCMAKE_RANLIB='/usr/local/opt/llvm/bin/llvm-ranlib' \
           " \
           --build-stdlib-deployment-targets "wasm-wasm32" \
           --build-swift-dynamic-sdk-overlay false \

CMakeLists.txt

@@ -850,11 +850,6 @@ if(swift_build_wasm AND NOT "${SWIFT_HOST_VARIANT_SDK}" STREQUAL "WASM")
   #  message(FATAL_ERROR "A Darwin or Linux host is required to build the Swift runtime for Android")
   #endif()
 
-  if ("${CMAKE_HOST_SYSTEM_NAME}" STREQUAL "Linux")
-    # WebAssembly: hack: use llvm-ar for creating static libraries; Ubuntu's GNU ar doesn't work with wasm-ld
-    set(CMAKE_AR "${SWIFT_WASM_WASI_SDK_PATH}/bin/llvm-ar")
-  endif()
-
   if("${SWIFT_SDK_WASM_ARCHITECTURES}" STREQUAL "")
     set(SWIFT_SDK_WASM_ARCHITECTURES wasm32)
   endif()

lib/IRGen/MetadataRequest.cpp

@@ -2271,14 +2271,19 @@ emitMetadataAccessByMangledName(IRGenFunction &IGF, CanType type,
                                                          IGM.Int32Ty);
       stringAddrOffset = subIGF.Builder.CreateSExtOrBitCast(stringAddrOffset,
                                                             IGM.SizeTy);
-      auto stringAddrBase = subIGF.Builder.CreatePtrToInt(cache, IGM.SizeTy);
-      if (IGM.getModule()->getDataLayout().isBigEndian()) {
-        stringAddrBase = subIGF.Builder.CreateAdd(stringAddrBase,
-                                        llvm::ConstantInt::get(IGM.SizeTy, 4));
+      llvm::Value *stringAddr;
+      if (IGM.TargetInfo.OutputObjectFormat == llvm::Triple::Wasm) {
+        stringAddr = subIGF.Builder.CreateIntToPtr(stringAddrOffset, IGM.Int8PtrTy);
+      } else {
+        auto stringAddrBase = subIGF.Builder.CreatePtrToInt(cache, IGM.SizeTy);
+        if (IGM.getModule()->getDataLayout().isBigEndian()) {
+          stringAddrBase = subIGF.Builder.CreateAdd(stringAddrBase,
+                                                    llvm::ConstantInt::get(IGM.SizeTy, 4));
+        }
+        stringAddr = subIGF.Builder.CreateAdd(stringAddrBase,
+                                                   stringAddrOffset);
+        stringAddr = subIGF.Builder.CreateIntToPtr(stringAddr, IGM.Int8PtrTy);
       }
-      auto stringAddr = subIGF.Builder.CreateAdd(stringAddrBase,
-                                                 stringAddrOffset);
-      stringAddr = subIGF.Builder.CreateIntToPtr(stringAddr, IGM.Int8PtrTy);
 
       auto call =
         subIGF.Builder.CreateCall(IGM.getGetTypeByMangledNameInContextFn(),

stdlib/public/runtime/CMakeLists.txt

@@ -89,8 +89,15 @@ set(swift_runtime_library_compile_flags ${swift_runtime_compile_flags})
 list(APPEND swift_runtime_library_compile_flags -DswiftCore_EXPORTS)
 list(APPEND swift_runtime_library_compile_flags -I${SWIFT_SOURCE_DIR}/include)
 
-set(sdk "${SWIFT_HOST_VARIANT_SDK}")
-if(SWIFT_BUILD_STATIC_STDLIB AND "${sdk}" STREQUAL "LINUX")
+set(image_inspection_shared_sdk)
+if(SWIFT_BUILD_STATIC_STDLIB AND "${SWIFT_HOST_VARIANT_SDK}" STREQUAL "LINUX")
+  set(image_inspection_shared_sdk "${SWIFT_HOST_VARIANT_SDK}")
+elseif("${SWIFT_PRIMARY_VARIANT_SDK}" STREQUAL "WASM")
+  set(image_inspection_shared_sdk "${SWIFT_PRIMARY_VARIANT_SDK}")
+endif()
+
+if(NOT "${image_inspection_shared_sdk}" STREQUAL "")
+  set(sdk "${image_inspection_shared_sdk}")
   list(REMOVE_ITEM swift_runtime_sources ImageInspectionELF.cpp)
   set(static_binary_lnk_file_list)
   string(TOLOWER "${sdk}" lowercase_sdk)

stdlib/public/runtime/SwiftRT-WASM.cpp

@@ -9,3 +9,78 @@
 // See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 //
 //===----------------------------------------------------------------------===//
+
+#include "ImageInspectionELF.h"
+
+#include <cstddef>
+
+// Create empty sections to ensure that the start/stop symbols are synthesized
+// by the linker.  Otherwise, we may end up with undefined symbol references as
+// the linker table section was never constructed.
+
+#define DECLARE_SWIFT_SECTION(name)                                                             \
+  __attribute__((__used__,__section__(#name),__aligned__(1))) const char __dummy_##name = 0x00; \
+  __attribute__((__visibility__("hidden"),__aligned__(1))) extern const char __start_##name;    \
+  __attribute__((__visibility__("hidden"),__aligned__(1))) extern const char __stop_##name;
+
+extern "C" {
+DECLARE_SWIFT_SECTION(swift5_protocols)
+DECLARE_SWIFT_SECTION(swift5_protocol_conformances)
+DECLARE_SWIFT_SECTION(swift5_type_metadata)
+
+DECLARE_SWIFT_SECTION(swift5_typeref)
+DECLARE_SWIFT_SECTION(swift5_reflstr)
+DECLARE_SWIFT_SECTION(swift5_fieldmd)
+DECLARE_SWIFT_SECTION(swift5_assocty)
+DECLARE_SWIFT_SECTION(swift5_replace)
+DECLARE_SWIFT_SECTION(swift5_replac2)
+DECLARE_SWIFT_SECTION(swift5_builtin)
+DECLARE_SWIFT_SECTION(swift5_capture)
+}
+
+#undef DECLARE_SWIFT_SECTION
+
+namespace {
+static swift::MetadataSections sections{};
+}
+
+__attribute__((__constructor__))
+static void swift_image_constructor() {
+#define SWIFT_SECTION_RANGE(name)                                              \
+  { reinterpret_cast<uintptr_t>(&__start_##name),                              \
+    static_cast<uintptr_t>(&__stop_##name - &__start_##name) }
+
+  sections = {
+      swift::CurrentSectionMetadataVersion,
+      0,
+
+      nullptr,
+      nullptr,
+
+      SWIFT_SECTION_RANGE(swift5_protocols),
+      SWIFT_SECTION_RANGE(swift5_protocol_conformances),
+      SWIFT_SECTION_RANGE(swift5_type_metadata),
+
+      SWIFT_SECTION_RANGE(swift5_typeref),
+      SWIFT_SECTION_RANGE(swift5_reflstr),
+      SWIFT_SECTION_RANGE(swift5_fieldmd),
+      SWIFT_SECTION_RANGE(swift5_assocty),
+      SWIFT_SECTION_RANGE(swift5_replace),
+      SWIFT_SECTION_RANGE(swift5_replac2),
+      SWIFT_SECTION_RANGE(swift5_builtin),
+      SWIFT_SECTION_RANGE(swift5_capture),
+  };
+
+#undef SWIFT_SECTION_RANGE
+
+  swift_addNewDSOImage(&sections);
+}
+
+static __attribute__((__used__))
+__attribute__((__section__(".note.swift_reflection_metadata")))
+__attribute__((__aligned__(1)))
+struct {
+  const char MagicString[sizeof(SWIFT_REFLECTION_METADATA_ELF_NOTE_MAGIC_STRING)];
+  const swift::MetadataSections *Sections;
+} __attribute__((__packed__))
+Note = {SWIFT_REFLECTION_METADATA_ELF_NOTE_MAGIC_STRING, &sections};