[asan] change the default mapping offset on x86_64 to 0x7fff8000. This gives roughly 5% speedup. Since this is an ABI change, bump the asan ABI version by renaming __asan_init to __asan_init_v1. llvm part, compiler-rt part will follow

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174957 91177308-0d34-0410-b5e6-96231b3b80d8

Author: kcc

lib/Transforms/Instrumentation/AddressSanitizer.cpp

@@ -68,7 +68,7 @@ static const char *kAsanRegisterGlobalsName = "__asan_register_globals";
 static const char *kAsanUnregisterGlobalsName = "__asan_unregister_globals";
 static const char *kAsanPoisonGlobalsName = "__asan_before_dynamic_init";
 static const char *kAsanUnpoisonGlobalsName = "__asan_after_dynamic_init";
-static const char *kAsanInitName = "__asan_init";
+static const char *kAsanInitName = "__asan_init_v1";
 static const char *kAsanHandleNoReturnName = "__asan_handle_no_return";
 static const char *kAsanMappingOffsetName = "__asan_mapping_offset";
 static const char *kAsanMappingScaleName = "__asan_mapping_scale";
@@ -136,7 +136,7 @@ static cl::opt<int> ClMappingOffsetLog("asan-mapping-offset-log",
        cl::desc("offset of asan shadow mapping"), cl::Hidden, cl::init(-1));
 static cl::opt<bool> ClShort64BitOffset("asan-short-64bit-mapping-offset",
        cl::desc("Use short immediate constant as the mapping offset for 64bit"),
-       cl::Hidden, cl::init(false));
+       cl::Hidden, cl::init(true));
 
 // Optimization flags. Not user visible, used mostly for testing
 // and benchmarking the tool.
@@ -203,6 +203,7 @@ static ShadowMapping getShadowMapping(const Module &M, int LongSize,
   llvm::Triple TargetTriple(M.getTargetTriple());
   bool IsAndroid = TargetTriple.getEnvironment() == llvm::Triple::Android;
   bool IsPPC64 = TargetTriple.getArch() == llvm::Triple::ppc64;
+  bool IsX86_64 = TargetTriple.getArch() == llvm::Triple::x86_64;
 
   ShadowMapping Mapping;
 
@@ -214,7 +215,8 @@ static ShadowMapping getShadowMapping(const Module &M, int LongSize,
   Mapping.Offset = (IsAndroid || ZeroBaseShadow) ? 0 :
       (LongSize == 32 ? kDefaultShadowOffset32 :
        IsPPC64 ? kPPC64_ShadowOffset64 : kDefaultShadowOffset64);
-  if (!ZeroBaseShadow && ClShort64BitOffset && LongSize == 64) {
+  if (!ZeroBaseShadow && ClShort64BitOffset && IsX86_64) {
+    assert(LongSize == 64);
     Mapping.Offset = kDefaultShort64bitShadowOffset;
   } if (!ZeroBaseShadow && ClMappingOffsetLog >= 0) {
     // Zero offset log is the special case.