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.

llvm-svn: 282403

1 files changed, 2 insertions, 3 deletions

diff --git a/compiler-rt/lib/tsan/rtl/tsan_platform.h b/compiler-rt/lib/tsan/rtl/tsan_platform.h
index f9c9eec82a3..506fa60f1b8 100644
--- a/compiler-rt/lib/tsan/rtl/tsan_platform.h
+++ b/compiler-rt/lib/tsan/rtl/tsan_platform.h
@@ -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);