Frontend: Define __SANITIZE_*__ macros for certain sanitizers.

Per discussion with @ojhunt and @AaronBallman we are moving towards
predefined macros and away from __has_feature and __has_extension
for detecting sanitizers and other similar features. The rationale
is that __has_feature is only really meant for standardized features
(see the comment at the top of clang/include/clang/Basic/Features.def),
and __has_extension has the issues discovered as part of llvm#153104.

Let's start by defining macros for ASan, HWASan and TSan, consistently
with gcc.

Reviewers: vitalybuka, ojhunt, AaronBallman, fmayer

Reviewed By: fmayer, vitalybuka

Pull Request: llvm#153888

Author: pcc

clang/lib/Frontend/InitPreprocessor.cpp

@@ -1519,6 +1519,13 @@ static void InitializePredefinedMacros(const TargetInfo &TI,
   if (TI.getTriple().isOSBinFormatELF())
     Builder.defineMacro("__ELF__");
 
+  if (LangOpts.Sanitize.has(SanitizerKind::Address))
+    Builder.defineMacro("__SANITIZE_ADDRESS__");
+  if (LangOpts.Sanitize.has(SanitizerKind::HWAddress))
+    Builder.defineMacro("__SANITIZE_HWADDRESS__");
+  if (LangOpts.Sanitize.has(SanitizerKind::Thread))
+    Builder.defineMacro("__SANITIZE_THREAD__");
+
   // Target OS macro definitions.
   if (PPOpts.DefineTargetOSMacros) {
     const llvm::Triple &Triple = TI.getTriple();

clang/test/Preprocessor/sanitizer-predefines.c

@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -E -dM -triple aarch64-unknown-linux -fsanitize=address %s | FileCheck %s --check-prefix=ASAN
+// ASAN: #define __SANITIZE_ADDRESS__ 1
+
+// RUN: %clang_cc1 -E -dM -triple aarch64-unknown-linux -fsanitize=hwaddress %s | FileCheck %s --check-prefix=HWASAN
+// HWASAN: #define __SANITIZE_HWADDRESS__ 1
+
+// RUN: %clang_cc1 -E -dM -triple aarch64-unknown-linux -fsanitize=thread %s | FileCheck %s --check-prefix=TSAN
+// TSAN: #define __SANITIZE_THREAD__ 1