[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

     COFF,
     ELF,
     MachO,
+    Wasm,
   };
 
 private:

     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 &&

lib/ProfileData/InstrProf.cpp

     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

lib/Support/Triple.cpp

     .EndsWith("coff", Triple::COFF)
     .EndsWith("elf", Triple::ELF)
     .EndsWith("macho", Triple::MachO)
+    .EndsWith("wasm", Triple::Wasm)
     .Default(Triple::UnknownObjectFormat);
 }
 

   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");
 }

lib/Transforms/Instrumentation/AddressSanitizer.cpp

     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.

unittests/ADT/TripleTest.cpp

   EXPECT_EQ(Triple::ELF, Triple("i686-pc-windows-msvc-elf").getObjectFormat());
   EXPECT_EQ(Triple::ELF, Triple("i686-pc-cygwin-elf").getObjectFormat());
 
+  EXPECT_EQ(Triple::Wasm, Triple("wasm32-unknown-unknown-wasm").getObjectFormat());
+  EXPECT_EQ(Triple::Wasm, Triple("wasm64-unknown-unknown-wasm").getObjectFormat());
+
   Triple MSVCNormalized(Triple::normalize("i686-pc-windows-msvc-elf"));
   EXPECT_EQ(Triple::ELF, MSVCNormalized.getObjectFormat());