[Swift+WASM] Allow Wasm object format.

- This currently does nothing more than adopt the ELF conventions, but for the
   Wasm object file format.

include/swift/Basic/Dwarf.h

@@ -27,6 +27,7 @@ namespace swift {
   static const char MachOASTSectionName[] = "__ast";
   static const char ELFASTSectionName[] = ".swift_ast";
   static const char COFFASTSectionName[] = "swiftast";
+  static const char WasmASTSectionName[] = ".swift_ast";
 } // end namespace swift
 
 #endif // SWIFT_BASIC_DWARF_H

lib/IRGen/GenClass.cpp

@@ -2050,9 +2050,10 @@ namespace {
         var->setSection(".data");
         break;
       case llvm::Triple::ELF:
+      case llvm::Triple::Wasm:
         var->setSection(".data");
         break;
-      default:
+      case llvm::Triple::UnknownObjectFormat:
         llvm_unreachable("Don't know how to emit private global constants for "
                          "the selected object format.");
       }

lib/IRGen/GenDecl.cpp

@@ -899,7 +899,7 @@ std::string IRGenModule::GetObjCSectionName(StringRef Section,
   case llvm::Triple::COFF:
     return ("." + Section.substr(2) + "$B").str();
   case llvm::Triple::Wasm:
-    error(SourceLoc(), "wasm is not a supported object file format");
+    return Section.substr(2).str();
   }
 
   llvm_unreachable("unexpected object file format");
@@ -930,7 +930,6 @@ void IRGenModule::SetCStringLiteralSection(llvm::GlobalVariable *GV,
   case llvm::Triple::COFF:
     return;
   case llvm::Triple::Wasm:
-    error(SourceLoc(), "wasm is not a supported object file format");
     return;
   }
 
@@ -1226,18 +1225,19 @@ void IRGenerator::noteUseOfTypeGlobals(NominalTypeDecl *type,
 static std::string getDynamicReplacementSection(IRGenModule &IGM) {
   std::string sectionName;
   switch (IGM.TargetInfo.OutputObjectFormat) {
+  case llvm::Triple::UnknownObjectFormat:
+    llvm_unreachable("Don't know how to emit field records table for "
+                     "the selected object format.");
   case llvm::Triple::MachO:
     sectionName = "__TEXT, __swift5_replace, regular, no_dead_strip";
     break;
   case llvm::Triple::ELF:
+  case llvm::Triple::Wasm:
     sectionName = "swift5_replace";
     break;
   case llvm::Triple::COFF:
     sectionName = ".sw5repl";
     break;
-  default:
-    llvm_unreachable("Don't know how to emit field records table for "
-                     "the selected object format.");
   }
   return sectionName;
 }
@@ -2700,18 +2700,19 @@ llvm::Constant *IRGenModule::emitSwiftProtocols() {
 
   StringRef sectionName;
   switch (TargetInfo.OutputObjectFormat) {
+  case llvm::Triple::UnknownObjectFormat:
+    llvm_unreachable("Don't know how to emit protocols for "
+                     "the selected object format.");
   case llvm::Triple::MachO:
     sectionName = "__TEXT, __swift5_protos, regular, no_dead_strip";
     break;
   case llvm::Triple::ELF:
+  case llvm::Triple::Wasm:
     sectionName = "swift5_protocols";
     break;
   case llvm::Triple::COFF:
     sectionName = ".sw5prt$B";
     break;
-  default:
-    llvm_unreachable("Don't know how to emit protocols for "
-                     "the selected object format.");
   }
 
   var->setSection(sectionName);
@@ -2772,18 +2773,19 @@ llvm::Constant *IRGenModule::emitProtocolConformances() {
 
   StringRef sectionName;
   switch (TargetInfo.OutputObjectFormat) {
+  case llvm::Triple::UnknownObjectFormat:
+    llvm_unreachable("Don't know how to emit protocol conformances for "
+                     "the selected object format.");
   case llvm::Triple::MachO:
     sectionName = "__TEXT, __swift5_proto, regular, no_dead_strip";
     break;
   case llvm::Triple::ELF:
+  case llvm::Triple::Wasm:
     sectionName = "swift5_protocol_conformances";
     break;
   case llvm::Triple::COFF:
     sectionName = ".sw5prtc$B";
     break;
-  default:
-    llvm_unreachable("Don't know how to emit protocol conformances for "
-                     "the selected object format.");
   }
 
   var->setSection(sectionName);
@@ -2803,12 +2805,13 @@ llvm::Constant *IRGenModule::emitTypeMetadataRecords() {
     sectionName = "__TEXT, __swift5_types, regular, no_dead_strip";
     break;
   case llvm::Triple::ELF:
+  case llvm::Triple::Wasm:
     sectionName = "swift5_type_metadata";
     break;
   case llvm::Triple::COFF:
     sectionName = ".sw5tymd$B";
     break;
-  default:
+  case llvm::Triple::UnknownObjectFormat:
     llvm_unreachable("Don't know how to emit type metadata table for "
                      "the selected object format.");
   }
@@ -2870,12 +2873,13 @@ llvm::Constant *IRGenModule::emitFieldDescriptors() {
     sectionName = "__TEXT, __swift5_fieldmd, regular, no_dead_strip";
     break;
   case llvm::Triple::ELF:
+  case llvm::Triple::Wasm:
     sectionName = "swift5_fieldmd";
     break;
   case llvm::Triple::COFF:
     sectionName = ".swift5_fieldmd";
     break;
-  default:
+  case llvm::Triple::UnknownObjectFormat:
     llvm_unreachable("Don't know how to emit field records table for "
                      "the selected object format.");
   }

lib/IRGen/GenMeta.cpp

@@ -119,7 +119,7 @@ void IRGenModule::setTrueConstGlobal(llvm::GlobalVariable *var) {
     var->setSection(".rdata");
     break;
   case llvm::Triple::Wasm:
-    llvm_unreachable("web assembly object format is not supported.");
+    var->setSection(".rodata");
     break;
   }
 }

lib/IRGen/GenReflection.cpp

@@ -869,6 +869,7 @@ static std::string getReflectionSectionName(IRGenModule &IGM,
     OS << ".sw5" << FourCC << "$B";
     break;
   case llvm::Triple::ELF:
+  case llvm::Triple::Wasm:
     OS << "swift5_" << LongName;
     break;
   case llvm::Triple::MachO:
@@ -876,9 +877,6 @@ static std::string getReflectionSectionName(IRGenModule &IGM,
            "Mach-O section name length must be <= 16 characters");
     OS << "__TEXT,__swift5_" << LongName << ", regular, no_dead_strip";
     break;
-  case llvm::Triple::Wasm:
-    llvm_unreachable("web assembly object format is not supported.");
-    break;
   }
   return OS.str();
 }

lib/IRGen/IRGen.cpp

@@ -1160,7 +1160,7 @@ swift::createSwiftModuleObjectFile(SILModule &SILMod, StringRef Buffer,
     Section = std::string(MachOASTSegmentName) + "," + MachOASTSectionName;
     break;
   case llvm::Triple::Wasm:
-    llvm_unreachable("web assembly object format is not supported.");
+    Section = WasmASTSectionName;
     break;
   }
   ASTSym->setSection(Section);

lib/IRGen/IRGenModule.cpp

@@ -1033,6 +1033,7 @@ void IRGenModule::emitAutolinkInfo() {
 
   } else {
     assert((TargetInfo.OutputObjectFormat == llvm::Triple::ELF ||
+            TargetInfo.OutputObjectFormat == llvm::Triple::Wasm ||
             Triple.isOSCygMing()) &&
            "expected ELF output format or COFF format for Cygwin/MinGW");