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
diff --git a/llvm/lib/IR/Attributes.cpp b/llvm/lib/IR/Attributes.cpp
index c8f1aaa..1b19a04 100644
--- a/llvm/lib/IR/Attributes.cpp
+++ b/llvm/lib/IR/Attributes.cpp
@@ -245,6 +245,8 @@
 
   if (hasAttribute(Attribute::SanitizeAddress))
     return "sanitize_address";
+  if (hasAttribute(Attribute::SanitizeHWAddress))
+    return "sanitize_hwaddress";
   if (hasAttribute(Attribute::AlwaysInline))
     return "alwaysinline";
   if (hasAttribute(Attribute::ArgMemOnly))
diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index 084eaba..26d2147 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -1375,6 +1375,7 @@
   case Attribute::NonLazyBind:
   case Attribute::ReturnsTwice:
   case Attribute::SanitizeAddress:
+  case Attribute::SanitizeHWAddress:
   case Attribute::SanitizeThread:
   case Attribute::SanitizeMemory:
   case Attribute::MinSize: