[compiler-rt] r282403 - tsan: simplify meta mapping

[Dmitry Vyukov via llvm-commits]

Author: dvyukov
Date: Mon Sep 26 08:24:48 2016
New Revision: 282403

URL: http://llvm.org/viewvc/llvm-project?rev=282403&view=rev
Log:
tsan: simplify meta mapping

Don't xor user address with kAppMemXor in meta mapping.
The only purpose of kAppMemXor is to raise shadow for ~0 user addresses,
so that they don't map to ~0 (which would cause overlap between
user memory and shadow).
For meta mapping we explicitly add kMetaShadowBeg offset,
so we don't need to additionally raise meta shadow.


Modified:
    compiler-rt/trunk/lib/tsan/rtl/tsan_platform.h

Modified: compiler-rt/trunk/lib/tsan/rtl/tsan_platform.h
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/tsan/rtl/tsan_platform.h?rev=282403&r1=282402&r2=282403&view=diff
==============================================================================
--- compiler-rt/trunk/lib/tsan/rtl/tsan_platform.h (original)
+++ compiler-rt/trunk/lib/tsan/rtl/tsan_platform.h Mon Sep 26 08:24:48 2016
@@ -662,9 +662,8 @@ template<typename Mapping>
 u32 *MemToMetaImpl(uptr x) {
   DCHECK(IsAppMem(x));
 #ifndef SANITIZER_GO
-  return (u32*)(((((x) & ~(Mapping::kAppMemMsk | (kMetaShadowCell - 1)))
-        ^ Mapping::kAppMemXor) / kMetaShadowCell * kMetaShadowSize)
-          | Mapping::kMetaShadowBeg);
+  return (u32*)(((((x) & ~(Mapping::kAppMemMsk | (kMetaShadowCell - 1)))) /
+      kMetaShadowCell * kMetaShadowSize) | Mapping::kMetaShadowBeg);
 #else
   return (u32*)(((x & ~(kMetaShadowCell - 1)) / \
       kMetaShadowCell * kMetaShadowSize) | Mapping::kMetaShadowBeg);