[WebAssembly] Add triple support for the new wasm object format

[sunfish]

Summary

The WebAssembly target is transitioning from ELF to a new binary object file format, for example in https://reviews.llvm.org/D26172 and so on. The patch here adds Triple support for this new format, in preparation for adding MC support.

[sunfish]

ping

[sunfish]

• rebase on trunk
• move the default object format for wasm32 and wasm64 back to ELF for now (it can be overridden by an explicit triple)

[sunfish]

ping

[sunfish]

ping

[echristo]

Needs some tests?

[sunfish]

• Add tests.

[sunfish]

• Fix accidentally deleted line in previous patch.

[sunfish]

In D26701#648544, @echristo wrote:

Needs some tests?

Quite so. Added.

[echristo]

I'm not quite sure why you need a new object format, but the patch is OK :)

-eric

include/llvm/ADT/Triple.h

enum EnvironmentType {
     LastEnvironmentType = OpenCL
   };
   enum ObjectFormatType {
     UnknownObjectFormat,
 
     COFF,
     ELF,
     MachO,
+    Wasm,
   };
 
 private:
   std::string Data;
 
   /// The parsed arch type.
   ArchType Arch;
 
bool isOSBinFormatCOFF() const {
     return getObjectFormat() == Triple::COFF;
   }
 
   /// Tests whether the environment is MachO.
   bool isOSBinFormatMachO() const {
     return getObjectFormat() == Triple::MachO;
   }
 
+  /// Tests whether the OS uses the Wasm binary format.
+  bool isOSBinFormatWasm() const {
+    return getObjectFormat() == Triple::Wasm;
+  }
+
   /// Tests whether the target is the PS4 CPU
   bool isPS4CPU() const {
     return getArch() == Triple::x86_64 &&
            getVendor() == Triple::SCEI &&
            getOS() == Triple::PS4;
   }
 
   /// Tests whether the target is the PS4 platform

lib/ProfileData/InstrProf.cpp

void createPGOFuncNameMetadata(Function &F, StringRef PGOFuncName) {
   F.setMetadata(getPGOFuncNameMetadataName(), N);
 }
 
 bool needsComdatForCounter(const Function &F, const Module &M) {
   if (F.hasComdat())
     return true;
 
   Triple TT(M.getTargetTriple());
-  if (!TT.isOSBinFormatELF())
+  if (!TT.isOSBinFormatELF() && !TT.isOSBinFormatWasm())
     return false;
 
   // See createPGOFuncNameVar for more details. To avoid link errors, profile
   // counters for function with available_externally linkage needs to be changed
   // to linkonce linkage. On ELF based systems, this leads to weak symbols to be
   // created. Without using comdat, duplicate entries won't be removed by the
   // linker leading to increased data segement size and raw profile size. Even
   // worse, since the referenced counter from profile per-function data object

lib/Support/Triple.cpp

return StringSwitch<Triple::EnvironmentType>(EnvironmentName)
     .Default(Triple::UnknownEnvironment);
 }
 
 static Triple::ObjectFormatType parseFormat(StringRef EnvironmentName) {
   return StringSwitch<Triple::ObjectFormatType>(EnvironmentName)
     .EndsWith("coff", Triple::COFF)
     .EndsWith("elf", Triple::ELF)
     .EndsWith("macho", Triple::MachO)
+    .EndsWith("wasm", Triple::Wasm)
     .Default(Triple::UnknownObjectFormat);
 }
 
 static Triple::SubArchType parseSubArch(StringRef SubArchName) {
   StringRef ARMSubArch = ARM::getCanonicalArchName(SubArchName);
 
   // For now, this is the small part. Early return.
   if (ARMSubArch.empty())

 }
 
 static StringRef getObjectFormatTypeName(Triple::ObjectFormatType Kind) {
   switch (Kind) {
   case Triple::UnknownObjectFormat: return "";
   case Triple::COFF: return "coff";
   case Triple::ELF: return "elf";
   case Triple::MachO: return "macho";
+  case Triple::Wasm: return "wasm";
   }
   llvm_unreachable("unknown object format type");
 }
 
 static Triple::ObjectFormatType getDefaultFormat(const Triple &T) {
   switch (T.getArch()) {
   case Triple::UnknownArch:
   case Triple::aarch64:

lib/Transforms/Instrumentation/AddressSanitizer.cpp

for (size_t i = 0; i < n; i++) {
     } else {
       SourceLoc = ConstantInt::get(IntptrTy, 0);
     }
 
     Constant *ODRIndicator = ConstantExpr::getNullValue(IRB.getInt8PtrTy());
     GlobalValue *InstrumentedGlobal = NewGlobal;
 
     bool CanUsePrivateAliases =
-        TargetTriple.isOSBinFormatELF() || TargetTriple.isOSBinFormatMachO();
+        TargetTriple.isOSBinFormatELF() || TargetTriple.isOSBinFormatMachO() ||
+        TargetTriple.isOSBinFormatWasm();
     if (CanUsePrivateAliases && ClUsePrivateAliasForGlobals) {
       // Create local alias for NewGlobal to avoid crash on ODR between
       // instrumented and non-instrumented libraries.
       auto *GA = GlobalAlias::create(GlobalValue::InternalLinkage,
                                      NameForGlobal + M.getName(), NewGlobal);
 
       // With local aliases, we need to provide another externally visible
       // symbol __odr_asan_XXX to detect ODR violation.