[clang] Support ASan on WASI (llvm#139014)

I'm working on porting ASan to Wasm/WASI targets, and this is the first
part of the change sets. I'll post runtime changes separately.

This change makes `-fsanitize=address` available for WASI target by
replicating what we do for Emscripten because they share the same memory
model.

Author: kateinoigakukun

clang/lib/Driver/ToolChains/WebAssembly.cpp

@@ -545,8 +545,13 @@ void WebAssembly::AddCXXStdlibLibArgs(const llvm::opt::ArgList &Args,
 SanitizerMask WebAssembly::getSupportedSanitizers() const {
   SanitizerMask Res = ToolChain::getSupportedSanitizers();
   if (getTriple().isOSEmscripten()) {
-    Res |= SanitizerKind::Vptr | SanitizerKind::Leak | SanitizerKind::Address;
+    Res |= SanitizerKind::Vptr | SanitizerKind::Leak;
   }
+
+  if (getTriple().isOSEmscripten() || getTriple().isOSWASI()) {
+    Res |= SanitizerKind::Address;
+  }
+
   // -fsanitize=function places two words before the function label, which are
   // -unsupported.
   Res &= ~SanitizerKind::Function;

llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp

@@ -118,7 +118,7 @@ static const uint64_t kNetBSD_ShadowOffset64 = 1ULL << 46;
 static const uint64_t kNetBSDKasan_ShadowOffset64 = 0xdfff900000000000;
 static const uint64_t kPS_ShadowOffset64 = 1ULL << 40;
 static const uint64_t kWindowsShadowOffset32 = 3ULL << 28;
-static const uint64_t kEmscriptenShadowOffset = 0;
+static const uint64_t kWebAssemblyShadowOffset = 0;
 
 // The shadow memory space is dynamically allocated.
 static const uint64_t kWindowsShadowOffset64 = kDynamicShadowSentinel;
@@ -499,9 +499,9 @@ static ShadowMapping getShadowMapping(const Triple &TargetTriple, int LongSize,
   bool IsRISCV64 = TargetTriple.getArch() == Triple::riscv64;
   bool IsWindows = TargetTriple.isOSWindows();
   bool IsFuchsia = TargetTriple.isOSFuchsia();
-  bool IsEmscripten = TargetTriple.isOSEmscripten();
   bool IsAMDGPU = TargetTriple.isAMDGPU();
   bool IsHaiku = TargetTriple.isOSHaiku();
+  bool IsWasm = TargetTriple.isWasm();
 
   ShadowMapping Mapping;
 
@@ -525,8 +525,8 @@ static ShadowMapping getShadowMapping(const Triple &TargetTriple, int LongSize,
       Mapping.Offset = kDynamicShadowSentinel;
     else if (IsWindows)
       Mapping.Offset = kWindowsShadowOffset32;
-    else if (IsEmscripten)
-      Mapping.Offset = kEmscriptenShadowOffset;
+    else if (IsWasm)
+      Mapping.Offset = kWebAssemblyShadowOffset;
     else
       Mapping.Offset = kDefaultShadowOffset32;
   } else {  // LongSize == 64