[WIP] [WebAssembly] Enable MemorySanitizer for emscripten

clang/lib/Driver/ToolChains/WebAssembly.cpp

case ToolChain::CST_Libstdcxx:
     CmdArgs.push_back("-lstdc++");
     break;
   }
 }
 
 SanitizerMask WebAssembly::getSupportedSanitizers() const {
   SanitizerMask Res = ToolChain::getSupportedSanitizers();
   if (getTriple().isOSEmscripten()) {
-    Res |= SanitizerKind::Vptr | SanitizerKind::Leak | SanitizerKind::Address;
+    Res |= SanitizerKind::Vptr;
+    Res |= SanitizerKind::Leak;
+    Res |= SanitizerKind::Address;
+    Res |= SanitizerKind::Memory;
   }
   return Res;
 }
 
 Tool *WebAssembly::buildLinker() const {
   return new tools::wasm::Linker(*this);
 }
 

llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp

 // x86_64 NetBSD
 static const MemoryMapParams NetBSD_X86_64_MemoryMapParams = {
     0,              // AndMask
     0x500000000000, // XorMask
     0,              // ShadowBase
     0x100000000000, // OriginBase
 };
 
+// wasm32 Emscripten
+static const MemoryMapParams Emscripten_wasm32_MemoryMapParams = {
+    0x000080000000, // AndMask
+    0,              // XorMask (not used)
+    0,              // ShadowBase (not used)
+    0x000040000000, // OriginBase
+};
+
+// wasm64 Emscripten
+static const MemoryMapParams Emscripten_wasm64_MemoryMapParams = {
+    0,              // AndMask (not used)
+    0x500000000000, // XorMask
+    0,              // ShadowBase (not used)
+    0x100000000000, // OriginBase
+};
+
 static const PlatformMemoryMapParams Linux_X86_MemoryMapParams = {
     &Linux_I386_MemoryMapParams,
     &Linux_X86_64_MemoryMapParams,
 };
 
 static const PlatformMemoryMapParams Linux_MIPS_MemoryMapParams = {
     nullptr,
     &Linux_MIPS64_MemoryMapParams,
static const PlatformMemoryMapParams FreeBSD_X86_MemoryMapParams = {
     &FreeBSD_X86_64_MemoryMapParams,
 };
 
 static const PlatformMemoryMapParams NetBSD_X86_MemoryMapParams = {
     nullptr,
     &NetBSD_X86_64_MemoryMapParams,
 };
 
+static const PlatformMemoryMapParams Emscripten_wasm_MemoryMapParams = {
+    &Emscripten_wasm32_MemoryMapParams,
+    &Emscripten_wasm64_MemoryMapParams,
+};
+
 namespace {
 
 /// Instrument functions of a module to detect uninitialized reads.
 ///
 /// Instantiating MemorySanitizer inserts the msan runtime library API function
 /// declarations into the module if they don't exist already. Instantiating
 /// ensures the __msan_init function is in the list of global constructors for
 /// the module.
case Triple::Linux:
       case Triple::aarch64:
       case Triple::aarch64_be:
         MapParams = Linux_ARM_MemoryMapParams.bits64;
         break;
       default:
         report_fatal_error("unsupported architecture");
       }
       break;
+    case Triple::Emscripten:
+      switch (TargetTriple.getArch()) {
+      case Triple::wasm32:
+        MapParams = Emscripten_wasm_MemoryMapParams.bits32;
+        break;
+      case Triple::wasm64:
+        MapParams = Emscripten_wasm_MemoryMapParams.bits64;
+        break;
+      default:
+        report_fatal_error("unsupported architecture");
+      }
+      break;
     default:
       report_fatal_error("unsupported operating system");
     }
   }
 
   C = &(M.getContext());
   IRBuilder<> IRB(*C);
   IntptrTy = IRB.getIntPtrTy(DL);