[asan] Enable -asan-use-private-alias on Darwin/Mach-O, add test for ODR false positive with LTO (llvm part)

The '-asan-use-private-alias’ option (disabled by default) option is currently only enabled for Linux and ELF, but it also works on Darwin and Mach-O. This option also fixes a known problem with LTO on Darwin (https://github.com/google/sanitizers/issues/647). This patch enables the support for Darwin (but still keeps it off by default) and adds the LTO test case.

Differential Revision: https://reviews.llvm.org/D24292

llvm-svn: 281470

llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp

@@ -1605,7 +1605,8 @@ bool AddressSanitizerModule::InstrumentGlobals(IRBuilder<> &IRB, Module &M) {
     Constant *ODRIndicator = ConstantExpr::getNullValue(IRB.getInt8PtrTy());
     GlobalValue *InstrumentedGlobal = NewGlobal;
 
-    bool CanUsePrivateAliases = TargetTriple.isOSBinFormatELF();
+    bool CanUsePrivateAliases =
+        TargetTriple.isOSBinFormatELF() || TargetTriple.isOSBinFormatMachO();
     if (CanUsePrivateAliases && ClUsePrivateAliasForGlobals) {
       // Create local alias for NewGlobal to avoid crash on ODR between
       // instrumented and non-instrumented libraries.