diff --git a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
--- a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -556,6 +556,22 @@
   }
 }
 
+// For a ret instruction followed by a musttail call, we cannot insert anything
+// in between. Instead we use the musttail call instruction as the insertion
+// point.
+static Instruction *adjustForMusttailCall(Instruction *I) {
+  ReturnInst *RI = dyn_cast<ReturnInst>(I);
+  if (!RI)
+    return I;
+  Instruction *Prev = RI->getPrevNode();
+  if (BitCastInst *BCI = dyn_cast_or_null<BitCastInst>(Prev))
+    Prev = BCI->getPrevNode();
+  if (CallInst *CI = dyn_cast_or_null<CallInst>(Prev))
+    if (CI->isMustTailCall())
+      return CI;
+  return RI;
+}
+
 namespace {
 
 /// Module analysis for getting various metadata about the module.
@@ -999,10 +1015,11 @@
 
   // Unpoison dynamic allocas redzones.
   void unpoisonDynamicAllocas() {
-    for (auto &Ret : RetVec)
-      unpoisonDynamicAllocasBeforeInst(Ret, DynamicAllocaLayout);
+    for (Instruction *Ret : RetVec)
+      unpoisonDynamicAllocasBeforeInst(adjustForMusttailCall(Ret),
+                                       DynamicAllocaLayout);
 
-    for (auto &StackRestoreInst : StackRestoreVec)
+    for (Instruction *StackRestoreInst : StackRestoreVec)
       unpoisonDynamicAllocasBeforeInst(StackRestoreInst,
                                        StackRestoreInst->getOperand(0));
   }
@@ -3303,8 +3320,9 @@
   SmallVector<uint8_t, 64> ShadowAfterReturn;
 
   // (Un)poison the stack before all ret instructions.
-  for (auto Ret : RetVec) {
-    IRBuilder<> IRBRet(Ret);
+  for (Instruction *Ret : RetVec) {
+    Instruction *Adjusted = adjustForMusttailCall(Ret);
+    IRBuilder<> IRBRet(Adjusted);
     // Mark the current frame as retired.
     IRBRet.CreateStore(ConstantInt::get(IntptrTy, kRetiredStackFrameMagic),
                        BasePlus0);
@@ -3323,7 +3341,7 @@
       Value *Cmp =
           IRBRet.CreateICmpNE(FakeStack, Constant::getNullValue(IntptrTy));
       Instruction *ThenTerm, *ElseTerm;
-      SplitBlockAndInsertIfThenElse(Cmp, Ret, &ThenTerm, &ElseTerm);
+      SplitBlockAndInsertIfThenElse(Cmp, Adjusted, &ThenTerm, &ElseTerm);
 
       IRBuilder<> IRBPoison(ThenTerm);
       if (StackMallocIdx <= 4) {
diff --git a/llvm/test/Instrumentation/AddressSanitizer/musttail.ll b/llvm/test/Instrumentation/AddressSanitizer/musttail.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Instrumentation/AddressSanitizer/musttail.ll
@@ -0,0 +1,35 @@
+; To test that asan does not break the musttail call contract.
+;
+; RUN: opt < %s -asan -asan-module -S -enable-new-pm=0 | FileCheck %s
+; RUN: opt < %s -passes='asan-pipeline' -S | FileCheck %s
+
+define internal i32 @foo(i32* %p) sanitize_address {
+  %rv = load i32, i32* %p
+  ret i32 %rv
+}
+
+declare void @alloca_test_use([10 x i8]*)
+define i32 @call_foo(i32* %a) sanitize_address {
+  %x = alloca [10 x i8], align 1
+  call void @alloca_test_use([10 x i8]* %x)
+  %r = musttail call i32 @foo(i32* %a)
+  ret i32 %r
+}
+
+; CHECK-LABEL:  define i32 @call_foo(i32* %a) 
+; CHECK:          %r = musttail call i32 @foo(i32* %a)
+; CHECK-NEXT:     ret i32 %r
+
+
+define i32 @call_foo_cast(i32* %a) sanitize_address {
+  %x = alloca [10 x i8], align 1
+  call void @alloca_test_use([10 x i8]* %x)
+  %r = musttail call i32 @foo(i32* %a)
+  %t = bitcast i32 %r to i32
+  ret i32 %t
+}
+
+; CHECK-LABEL:  define i32 @call_foo_cast(i32* %a)
+; CHECK:          %r = musttail call i32 @foo(i32* %a)
+; CHECK-NEXT:     %t = bitcast i32 %r to i32
+; CHECK-NEXT:     ret i32 %t