new file mode 100644
--- /dev/null
+++ b/build/build-clang/alias.patch
@@ -0,0 +1,16 @@
+Index: lib/Transforms/IPO/LowerTypeTests.cpp
+===================================================================
+--- a/llvm/lib/Transforms/IPO/LowerTypeTests.cpp	(revision 332262)
++++ b/llvm/lib/Transforms/IPO/LowerTypeTests.cpp	(working copy)
+@@ -1716,6 +1716,11 @@
+           F->clearMetadata();
+         }
+
++	 // Update the linkage for extern_weak declarations when a definition
++        // exists.
++        if (Linkage == CFL_Definition && F->hasExternalWeakLinkage())
++          F->setLinkage(GlobalValue::ExternalLinkage);
++
+         // If the function in the full LTO module is a declaration, replace its
+         // type metadata with the type metadata we found in cfi.functions. That
+         // metadata is presumed to be more accurate than the metadata attached

--- a/build/build-clang/clang-6-linux64.json
+++ b/build/build-clang/clang-6-linux64.json
@@ -1,20 +1,20 @@
 {
-    "llvm_revision": "326563",
+    "llvm_revision": "334637",
     "stages": "3",
     "build_libcxx": true,
     "build_type": "Release",
     "assertions": false,
-    "llvm_repo": "https://llvm.org/svn/llvm-project/llvm/tags/RELEASE_600/final",
-    "clang_repo": "https://llvm.org/svn/llvm-project/cfe/tags/RELEASE_600/final",
-    "lld_repo": "https://llvm.org/svn/llvm-project/lld/tags/RELEASE_600/final",
-    "compiler_repo": "https://llvm.org/svn/llvm-project/compiler-rt/tags/RELEASE_600/final",
-    "libcxx_repo": "https://llvm.org/svn/llvm-project/libcxx/tags/RELEASE_600/final",
-    "libcxxabi_repo": "https://llvm.org/svn/llvm-project/libcxxabi/tags/RELEASE_600/final",
+    "llvm_repo": "https://llvm.org/svn/llvm-project/llvm/trunk",
+    "clang_repo": "https://llvm.org/svn/llvm-project/cfe/trunk",
+    "lld_repo": "https://llvm.org/svn/llvm-project/lld/trunk",
+    "compiler_repo": "https://llvm.org/svn/llvm-project/compiler-rt/trunk",
+    "libcxx_repo": "https://llvm.org/svn/llvm-project/libcxx/trunk",
+    "libcxxabi_repo": "https://llvm.org/svn/llvm-project/libcxxabi/trunk",
     "python_path": "/usr/bin/python2.7",
     "gcc_dir": "/builds/worker/workspace/build/src/gcc",
     "cc": "/builds/worker/workspace/build/src/gcc/bin/gcc",
     "cxx": "/builds/worker/workspace/build/src/gcc/bin/g++",
     "as": "/builds/worker/workspace/build/src/gcc/bin/gcc",
     "patches": [
       "find_symbolizer_linux.patch"
     ]

old mode 100755
new mode 100644
--- a/build/moz.configure/toolchain.configure
+++ b/build/moz.configure/toolchain.configure
@@ -1337,16 +1337,26 @@ def lto(value, c_compiler):
 
         if len(value) and value[0].lower() == 'full':
             flags.append("-flto")
             ldflags.append("-flto")
         elif value:
             flags.append("-flto=thin")
             ldflags.append("-flto=thin")
 
+            flags.append("-fsanitize=cfi-icall")
+            flags.append("-fsanitize-cfi-icall-generalize-pointers")
+            flags.append("-fno-sanitize-trap=cfi")
+            flags.append("-fsanitize-recover=cfi")
+
+            ldflags.append("-fsanitize=cfi-icall")
+            ldflags.append("-fsanitize-cfi-icall-generalize-pointers")
+            ldflags.append("-fno-sanitize-trap=cfi")
+            ldflags.append("-fsanitize-recover=cfi")
+
     # gcc and other compilers
     elif value:
         num_cores = multiprocessing.cpu_count()
         flags.append("-flto")
         flags.append("-flifetime-dse=1")
 
         ldflags.append("-flto=%s" % num_cores)
         ldflags.append("-flifetime-dse=1")

--- a/config/rules.mk
+++ b/config/rules.mk
@@ -912,17 +912,17 @@ ifneq (WINNT,$(OS_ARCH))
 # some crates's build scripts (!), so disable it for now.
 ifndef MOZ_ASAN
 ifndef MOZ_TSAN
 # Cargo needs the same linker flags as the C/C++ compiler,
 # but not the final libraries. Filter those out because they
 # cause problems on macOS 10.7; see bug 1365993 for details.
 # Also, we don't want to pass PGO flags until cargo supports them.
 target_cargo_env_vars := \
-	MOZ_CARGO_WRAP_LDFLAGS="$(filter-out -framework Cocoa -lobjc AudioToolbox ExceptionHandling -fprofile-%,$(LDFLAGS))" \
+	MOZ_CARGO_WRAP_LDFLAGS="$(filter-out -fsanitize=cfi% -framework Cocoa -lobjc AudioToolbox ExceptionHandling -fprofile-%,$(LDFLAGS))" \
 	MOZ_CARGO_WRAP_LD="$(CC)" \
 	$(cargo_linker_env_var)=$(topsrcdir)/build/cargo-linker
 endif # MOZ_TSAN
 endif # MOZ_ASAN
 
 endif # ifneq WINNT
 
 ifdef RUST_LIBRARY_FILE