Hardware-assisted AddressSanitizer (llvm part).

Summary:
This is LLVM instrumentation for the new HWASan tool. It is basically
a stripped down copy of ASan at this point, w/o stack or global
support. Instrumenation adds a global constructor + runtime callbacks
for every load and store.

HWASan comes with its own IR attribute.

A brief design document can be found in
clang/docs/HardwareAssistedAddressSanitizerDesign.rst (submitted earlier).

Reviewers: kcc, pcc, alekseyshl

Subscribers: srhines, mehdi_amini, mgorny, javed.absar, eraman, llvm-commits, hiraditya

Differential Revision: https://reviews.llvm.org/D40932

llvm-svn: 320217

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -663,6 +663,8 @@ static uint64_t getAttrKindEncoding(Attribute::AttrKind Kind) {
     return bitc::ATTR_KIND_STRUCT_RET;
   case Attribute::SanitizeAddress:
     return bitc::ATTR_KIND_SANITIZE_ADDRESS;
+  case Attribute::SanitizeHWAddress:
+    return bitc::ATTR_KIND_SANITIZE_HWADDRESS;
   case Attribute::SanitizeThread:
     return bitc::ATTR_KIND_SANITIZE_THREAD;
   case Attribute::SanitizeMemory: