Add documentation of new sanitizer-specific GV attributes.

llvm/docs/LangRef.rst

Syntax::
 
       @<GlobalVarName> = [Linkage] [PreemptionSpecifier] [Visibility]
                          [DLLStorageClass] [ThreadLocal]
                          [(unnamed_addr|local_unnamed_addr)] [AddrSpace]
                          [ExternallyInitialized]
                          <global | constant> <Type> [<InitializerConstant>]
                          [, section "name"] [, partition "name"]
                          [, comdat [($name)]] [, align <Alignment>]
+                         [, no_sanitize] [, no_sanitize_address]
+                         [, no_sanitize_hwaddress] [, sanitize_address_dyninit]
                          (, !name !N)*
 
 For example, the following defines a global in a numbered address space
 with an initializer, section, and alignment:
 
 .. code-block:: llvm
 
     @G = addrspace(5) constant float 1.0, section "foo", align 4

 
 Global Attributes
 -----------------
 
 Attributes may be set to communicate additional information about a global variable.
 Unlike :ref:`function attributes <fnattrs>`, attributes on a global variable
 are grouped into a single :ref:`attribute group <attrgrp>`.
 
+``no_sanitize``
+    This attribute indicates that the global variable should not have any
+    sanitizers applied to it, either because it was in the sanitizer ignore
+    list, or it was annotated with
+    `__attribute__((disable_sanitizer_instrumentation))`.
+``no_sanitize_address``
+    This attribute indicates that the global variable should not have
+    AddressSanitizer instrumentation applied to it, because it was annotated
+    with `__attribute__((no_sanitize("address")))`.
+``no_sanitize_hwaddress``
+    This attribute indicates that the global variable should not have
+    HWAddressSanitizer instrumentation applied to it, because it was annotated
+    with `__attribute__((no_sanitize("hwaddress")))`.
+``sanitize_address_dyninit``
+    This attribute indicates that the global variable, when instrumented with
+    AddressSanitizer, should be checked for ODR violations. This attribute is
+    applied to global variables that are dynamically initialized according to
+    C++ rules.
+
 .. _opbundles:
 
 Operand Bundles
 ---------------
 
 Operand bundles are tagged sets of SSA values that can be associated
 with certain LLVM instructions (currently only ``call`` s and
 ``invoke`` s).  In a way they are like metadata, but dropping them is