Index: llvm/trunk/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
+++ llvm/trunk/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
@@ -101,6 +101,11 @@
     cl::desc("offset of hwasan shadow mapping [EXPERIMENTAL]"), cl::Hidden,
     cl::init(0));
 
+static cl::opt<int> ClMatchAllTag(
+    "hwasan-match-all-tag",
+    cl::desc("don't report bad accesses via pointers with this tag"), cl::Hidden,
+    cl::init(-1));
+
 static cl::opt<bool> ClEnableKhwasan(
     "hwasan-kernel", cl::desc("Enable KernelHWAddressSanitizer instrumentation"),
     cl::Hidden, cl::init(false));
@@ -330,6 +335,12 @@
       IRB.CreateLoad(IRB.CreateIntToPtr(ShadowLong, IRB.getInt8PtrTy()));
   Value *TagMismatch = IRB.CreateICmpNE(PtrTag, MemTag);
 
+  if (ClMatchAllTag != -1) {
+    Value *TagNotIgnored = IRB.CreateICmpNE(PtrTag,
+        ConstantInt::get(PtrTag->getType(), ClMatchAllTag));
+    TagMismatch = IRB.CreateAnd(TagMismatch, TagNotIgnored);
+  }
+
   TerminatorInst *CheckTerm =
       SplitBlockAndInsertIfThen(TagMismatch, InsertBefore, !Recover,
                                 MDBuilder(*C).createBranchWeights(1, 100000));
Index: llvm/trunk/test/Instrumentation/HWAddressSanitizer/kernel.ll
===================================================================
--- llvm/trunk/test/Instrumentation/HWAddressSanitizer/kernel.ll
+++ llvm/trunk/test/Instrumentation/HWAddressSanitizer/kernel.ll
@@ -1,10 +1,11 @@
 ; Test kernel hwasan instrumentation.
 ;
 ; RUN: opt < %s -hwasan -hwasan-kernel=1 -S | FileCheck %s --allow-empty --check-prefixes=INIT
-; RUN: opt < %s -hwasan -hwasan-kernel=1 -S | FileCheck %s  --check-prefixes=CHECK,NOOFFSET
-; RUN: opt < %s -hwasan -hwasan-kernel=1 -hwasan-mapping-offset=12345678 -S | FileCheck %s  --check-prefixes=CHECK,OFFSET
-; RUN: opt < %s -hwasan -hwasan-kernel=1 -hwasan-recover=0 -S | FileCheck %s  --check-prefixes=CHECK,NOOFFSET,ABORT
-; RUN: opt < %s -hwasan -hwasan-kernel=1 -hwasan-recover=1 -S | FileCheck %s  --check-prefixes=CHECK,NOOFFSET,RECOVER
+; RUN: opt < %s -hwasan -hwasan-kernel=1 -S | FileCheck %s  --check-prefixes=CHECK,NOOFFSET,NO-MATCH-ALL
+; RUN: opt < %s -hwasan -hwasan-kernel=1 -hwasan-mapping-offset=12345678 -S | FileCheck %s  --check-prefixes=CHECK,OFFSET,NO-MATCH-ALL
+; RUN: opt < %s -hwasan -hwasan-kernel=1 -hwasan-recover=0 -S | FileCheck %s  --check-prefixes=CHECK,NOOFFSET,ABORT,NO-MATCH-ALL
+; RUN: opt < %s -hwasan -hwasan-kernel=1 -hwasan-recover=1 -S | FileCheck %s  --check-prefixes=CHECK,NOOFFSET,RECOVER,NO-MATCH-ALL
+; RUN: opt < %s -hwasan -hwasan-kernel=1 -hwasan-recover=1 -hwasan-match-all-tag=0xff -S | FileCheck %s  --check-prefixes=CHECK,NOOFFSET,RECOVER,MATCH-ALL
 
 target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
 target triple = "aarch64--linux-android"
@@ -24,7 +25,12 @@
 
 ; CHECK: %[[MEMTAG:[^ ]*]] = load i8, i8* %[[E]]
 ; CHECK: %[[F:[^ ]*]] = icmp ne i8 %[[PTRTAG]], %[[MEMTAG]]
-; CHECK: br i1 %[[F]], label {{.*}}, label {{.*}}, !prof {{.*}}
+
+; MATCH-ALL: %[[G:[^ ]*]] = icmp ne i8 %[[PTRTAG]], -1
+; MATCH-ALL: %[[H:[^ ]*]] = and i1 %[[F]], %[[G]]
+; MATCH-ALL: br i1 %[[H]], label {{.*}}, label {{.*}}, !prof {{.*}}
+
+; NO-MATCH-ALL: br i1 %[[F]], label {{.*}}, label {{.*}}, !prof {{.*}}
 
 ; ABORT: call void asm sideeffect "brk #2304", "{x0}"(i64 %[[A]])
 ; ABORT: unreachable