diff --git a/compiler-rt/test/hwasan/TestCases/stack-uas.c b/compiler-rt/test/hwasan/TestCases/stack-uas.c
--- a/compiler-rt/test/hwasan/TestCases/stack-uas.c
+++ b/compiler-rt/test/hwasan/TestCases/stack-uas.c
@@ -1,16 +1,16 @@
 // Tests use-after-scope detection and reporting.
-// RUN: %clang_hwasan -mllvm -hwasan-use-after-scope -g %s -o %t && not %run %t 2>&1 | FileCheck %s
-// RUN: %clang_hwasan -mllvm -hwasan-use-after-scope -g %s -o %t && not %env_hwasan_opts=symbolize=0 %run %t 2>&1 | FileCheck %s --check-prefix=NOSYM
+// RUN: %clang_hwasan -g %s -o %t && not %run %t 2>&1 | FileCheck %s
+// RUN: %clang_hwasan -g %s -o %t && not %env_hwasan_opts=symbolize=0 %run %t 2>&1 | FileCheck %s --check-prefix=NOSYM
+// Use after scope is turned on by default.
+// RUN: %clang_hwasan -g %s -o %t && not %run %t 2>&1 | FileCheck %s
 
 // RUN: %clang_hwasan -mllvm -hwasan-use-after-scope=false -g %s -o %t && %run %t 2>&1
-// Use after scope is turned off by default.
-// RUN: %clang_hwasan -g %s -o %t && %run %t 2>&1
 
-// RUN: %clang_hwasan -mllvm -hwasan-use-after-scope -g %s -o %t && not %run %t 2>&1 | FileCheck %s
+// RUN: %clang_hwasan -g %s -o %t && not %run %t 2>&1 | FileCheck %s
 
 // Run the same test as above, but using the __hwasan_add_frame_record libcall.
 // The output should be the exact same.
-// RUN: %clang_hwasan -mllvm -hwasan-use-after-scope -mllvm -hwasan-record-stack-history=libcall -g %s -o %t && not %env_hwasan_opts=symbolize=0 %run %t 2>&1 | FileCheck %s --check-prefix=NOSYM
+// RUN: %clang_hwasan -mllvm -hwasan-record-stack-history=libcall -g %s -o %t && not %env_hwasan_opts=symbolize=0 %run %t 2>&1 | FileCheck %s --check-prefix=NOSYM
 
 // REQUIRES: stable-runtime
 
diff --git a/compiler-rt/test/hwasan/TestCases/use-after-scope-capture.cpp b/compiler-rt/test/hwasan/TestCases/use-after-scope-capture.cpp
--- a/compiler-rt/test/hwasan/TestCases/use-after-scope-capture.cpp
+++ b/compiler-rt/test/hwasan/TestCases/use-after-scope-capture.cpp
@@ -1,6 +1,6 @@
 // This is the ASAN test of the same name ported to HWAsan.
 
-// RUN: %clangxx_hwasan -mllvm -hwasan-use-after-scope --std=c++11 -O1 %s -o %t && not %run %t 2>&1 | FileCheck %s
+// RUN: %clangxx_hwasan --std=c++11 -O1 %s -o %t && not %run %t 2>&1 | FileCheck %s
 
 // REQUIRES: aarch64-target-arch || riscv64-target-arch
 // REQUIRES: stable-runtime
diff --git a/compiler-rt/test/hwasan/TestCases/use-after-scope-dtor-order.cpp b/compiler-rt/test/hwasan/TestCases/use-after-scope-dtor-order.cpp
--- a/compiler-rt/test/hwasan/TestCases/use-after-scope-dtor-order.cpp
+++ b/compiler-rt/test/hwasan/TestCases/use-after-scope-dtor-order.cpp
@@ -1,6 +1,6 @@
 // This is the ASAN test of the same name ported to HWAsan.
 
-// RUN: %clangxx_hwasan -mllvm -hwasan-use-after-scope -O1 %s -o %t && \
+// RUN: %clangxx_hwasan -O1 %s -o %t && \
 // RUN:     not %run %t 2>&1 | FileCheck %s
 
 // REQUIRES: aarch64-target-arch || riscv64-target-arch
diff --git a/compiler-rt/test/hwasan/TestCases/use-after-scope-goto.cpp b/compiler-rt/test/hwasan/TestCases/use-after-scope-goto.cpp
--- a/compiler-rt/test/hwasan/TestCases/use-after-scope-goto.cpp
+++ b/compiler-rt/test/hwasan/TestCases/use-after-scope-goto.cpp
@@ -1,6 +1,6 @@
 // This is the ASAN test of the same name ported to HWAsan.
 
-// RUN: %clangxx_hwasan -mllvm -hwasan-use-after-scope -O0 %s -o %t && %run %t
+// RUN: %clangxx_hwasan -O0 %s -o %t && %run %t
 
 // Function jumps over variable initialization making lifetime analysis
 // ambiguous. Asan should ignore such variable and program must not fail.
diff --git a/compiler-rt/test/hwasan/TestCases/use-after-scope-if.cpp b/compiler-rt/test/hwasan/TestCases/use-after-scope-if.cpp
--- a/compiler-rt/test/hwasan/TestCases/use-after-scope-if.cpp
+++ b/compiler-rt/test/hwasan/TestCases/use-after-scope-if.cpp
@@ -1,6 +1,6 @@
 // This is the ASAN test of the same name ported to HWAsan.
 
-// RUN: %clangxx_hwasan -mllvm -hwasan-use-after-scope -O1 %s -o %t && \
+// RUN: %clangxx_hwasan -O1 %s -o %t && \
 // RUN:     not %run %t 2>&1 | FileCheck %s
 
 // REQUIRES: aarch64-target-arch || riscv64-target-arch
diff --git a/compiler-rt/test/hwasan/TestCases/use-after-scope-inlined.cpp b/compiler-rt/test/hwasan/TestCases/use-after-scope-inlined.cpp
--- a/compiler-rt/test/hwasan/TestCases/use-after-scope-inlined.cpp
+++ b/compiler-rt/test/hwasan/TestCases/use-after-scope-inlined.cpp
@@ -4,7 +4,7 @@
 // happens. "always_inline" is not enough, as Clang doesn't emit
 // llvm.lifetime intrinsics at -O0.
 //
-// RUN: %clangxx_hwasan -mllvm -hwasan-use-after-scope -O2 %s -o %t && \
+// RUN: %clangxx_hwasan -O2 %s -o %t && \
 // RUN:     not %run %t 2>&1 | FileCheck %s
 
 // REQUIRES: aarch64-target-arch || riscv64-target-arch
diff --git a/compiler-rt/test/hwasan/TestCases/use-after-scope-loop-bug.cpp b/compiler-rt/test/hwasan/TestCases/use-after-scope-loop-bug.cpp
--- a/compiler-rt/test/hwasan/TestCases/use-after-scope-loop-bug.cpp
+++ b/compiler-rt/test/hwasan/TestCases/use-after-scope-loop-bug.cpp
@@ -1,6 +1,6 @@
 // This is the ASAN test of the same name ported to HWAsan.
 
-// RUN: %clangxx_hwasan -mllvm -hwasan-use-after-scope -O1 %s -o %t && \
+// RUN: %clangxx_hwasan -O1 %s -o %t && \
 // RUN:     not %run %t 2>&1 | FileCheck %s
 
 // REQUIRES: aarch64-target-arch || riscv64-target-arch
diff --git a/compiler-rt/test/hwasan/TestCases/use-after-scope-loop-removed.cpp b/compiler-rt/test/hwasan/TestCases/use-after-scope-loop-removed.cpp
--- a/compiler-rt/test/hwasan/TestCases/use-after-scope-loop-removed.cpp
+++ b/compiler-rt/test/hwasan/TestCases/use-after-scope-loop-removed.cpp
@@ -1,6 +1,6 @@
 // This is the ASAN test of the same name ported to HWAsan.
 
-// RUN: %clangxx_hwasan -mllvm -hwasan-use-after-scope -O1 %s -o %t && \
+// RUN: %clangxx_hwasan -O1 %s -o %t && \
 // RUN:     not %run %t 2>&1 | FileCheck %s
 
 // REQUIRES: aarch64-target-arch || riscv64-target-arch
diff --git a/compiler-rt/test/hwasan/TestCases/use-after-scope-loop.cpp b/compiler-rt/test/hwasan/TestCases/use-after-scope-loop.cpp
--- a/compiler-rt/test/hwasan/TestCases/use-after-scope-loop.cpp
+++ b/compiler-rt/test/hwasan/TestCases/use-after-scope-loop.cpp
@@ -1,6 +1,6 @@
 // This is the ASAN test of the same name ported to HWAsan.
 
-// RUN: %clangxx_hwasan -mllvm -hwasan-use-after-scope -O1 %s -o %t && \
+// RUN: %clangxx_hwasan -O1 %s -o %t && \
 // RUN:     not %run %t 2>&1 | FileCheck %s
 
 // REQUIRES: aarch64-target-arch || riscv64-target-arch
diff --git a/compiler-rt/test/hwasan/TestCases/use-after-scope-nobug.cpp b/compiler-rt/test/hwasan/TestCases/use-after-scope-nobug.cpp
--- a/compiler-rt/test/hwasan/TestCases/use-after-scope-nobug.cpp
+++ b/compiler-rt/test/hwasan/TestCases/use-after-scope-nobug.cpp
@@ -1,6 +1,6 @@
 // This is the ASAN test of the same name ported to HWAsan.
 
-// RUN: %clangxx_hwasan -mllvm -hwasan-use-after-scope -O1 %s -o %t && %run %t
+// RUN: %clangxx_hwasan -O1 %s -o %t && %run %t
 
 // REQUIRES: aarch64-target-arch || riscv64-target-arch
 // REQUIRES: stable-runtime
diff --git a/compiler-rt/test/hwasan/TestCases/use-after-scope-setjmp.cpp b/compiler-rt/test/hwasan/TestCases/use-after-scope-setjmp.cpp
--- a/compiler-rt/test/hwasan/TestCases/use-after-scope-setjmp.cpp
+++ b/compiler-rt/test/hwasan/TestCases/use-after-scope-setjmp.cpp
@@ -1,4 +1,4 @@
-// RUN: %clangxx_hwasan  -mllvm -hwasan-use-stack-safety=0 -mllvm -hwasan-use-after-scope -O2 %s -o %t && \
+// RUN: %clangxx_hwasan  -mllvm -hwasan-use-stack-safety=0 -O2 %s -o %t && \
 // RUN:     %run %t 2>&1
 
 // REQUIRES: aarch64-target-arch || riscv64-target-arch
diff --git a/compiler-rt/test/hwasan/TestCases/use-after-scope-temp.cpp b/compiler-rt/test/hwasan/TestCases/use-after-scope-temp.cpp
--- a/compiler-rt/test/hwasan/TestCases/use-after-scope-temp.cpp
+++ b/compiler-rt/test/hwasan/TestCases/use-after-scope-temp.cpp
@@ -1,6 +1,6 @@
 // This is the ASAN test of the same name ported to HWAsan.
 
-// RUN: %clangxx_hwasan -mllvm -hwasan-use-after-scope -std=c++11 -O1 %s -o %t && \
+// RUN: %clangxx_hwasan -std=c++11 -O1 %s -o %t && \
 // RUN:     not %run %t 2>&1 | FileCheck %s
 
 // REQUIRES: aarch64-target-arch || riscv64-target-arch
diff --git a/compiler-rt/test/hwasan/TestCases/use-after-scope-temp2.cpp b/compiler-rt/test/hwasan/TestCases/use-after-scope-temp2.cpp
--- a/compiler-rt/test/hwasan/TestCases/use-after-scope-temp2.cpp
+++ b/compiler-rt/test/hwasan/TestCases/use-after-scope-temp2.cpp
@@ -1,6 +1,6 @@
 // This is the ASAN test of the same name ported to HWAsan.
 
-// RUN: %clangxx_hwasan -mllvm -hwasan-use-after-scope -std=c++11 -O1 %s -o %t && \
+// RUN: %clangxx_hwasan -std=c++11 -O1 %s -o %t && \
 // RUN:     not %run %t 2>&1 | FileCheck %s
 
 // REQUIRES: aarch64-target-arch || riscv64-target-arch
diff --git a/compiler-rt/test/hwasan/TestCases/use-after-scope-types.cpp b/compiler-rt/test/hwasan/TestCases/use-after-scope-types.cpp
--- a/compiler-rt/test/hwasan/TestCases/use-after-scope-types.cpp
+++ b/compiler-rt/test/hwasan/TestCases/use-after-scope-types.cpp
@@ -1,7 +1,7 @@
 // This is the ASAN test of the same name ported to HWAsan.
 
-// RUN: %clangxx_hwasan -mllvm -hwasan-use-after-scope -std=c++11 -O0 %s -o %t
-// RUN: %clangxx_hwasan -fno-exceptions -mllvm -hwasan-use-after-scope -std=c++11 -O0 %s -o %t-noexcept
+// RUN: %clangxx_hwasan -std=c++11 -O0 %s -o %t
+// RUN: %clangxx_hwasan -fno-exceptions -std=c++11 -O0 %s -o %t-noexcept
 
 // RUN: not %run %t 0 2>&1 | FileCheck %s
 // RUN: not %run %t 1 2>&1 | FileCheck %s
diff --git a/compiler-rt/test/hwasan/TestCases/use-after-scope.cpp b/compiler-rt/test/hwasan/TestCases/use-after-scope.cpp
--- a/compiler-rt/test/hwasan/TestCases/use-after-scope.cpp
+++ b/compiler-rt/test/hwasan/TestCases/use-after-scope.cpp
@@ -1,6 +1,6 @@
 // This is the ASAN test of the same name ported to HWAsan.
 
-// RUN: %clangxx_hwasan -mllvm -hwasan-use-after-scope -O1 %s -o %t && \
+// RUN: %clangxx_hwasan -O1 %s -o %t \
 // RUN:     not %run %t 2>&1 | FileCheck %s
 
 // REQUIRES: aarch64-target-arch || riscv64-target-arch
diff --git a/llvm/docs/ReleaseNotes.rst b/llvm/docs/ReleaseNotes.rst
--- a/llvm/docs/ReleaseNotes.rst
+++ b/llvm/docs/ReleaseNotes.rst
@@ -133,6 +133,7 @@
 
 Changes to Sanitizers
 ---------------------
+* HWASan now defaults to detecting use-after-scope bugs.
 
 Other Changes
 -------------
diff --git a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
--- a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
@@ -134,7 +134,7 @@
 static cl::opt<bool>
     ClUseAfterScope("hwasan-use-after-scope",
                     cl::desc("detect use after scope within function"),
-                    cl::Hidden, cl::init(false));
+                    cl::Hidden, cl::init(true));
 
 static cl::opt<bool> ClGenerateTagsWithCalls(
     "hwasan-generate-tags-with-calls",
diff --git a/llvm/test/Instrumentation/HWAddressSanitizer/X86/alloca.ll b/llvm/test/Instrumentation/HWAddressSanitizer/X86/alloca.ll
--- a/llvm/test/Instrumentation/HWAddressSanitizer/X86/alloca.ll
+++ b/llvm/test/Instrumentation/HWAddressSanitizer/X86/alloca.ll
@@ -109,6 +109,7 @@
 ; CHECK-NEXT:    [[TMP8:%.*]] = shl i64 [[TMP5]], 57
 ; CHECK-NEXT:    [[TMP9:%.*]] = or i64 [[TMP7]], [[TMP8]]
 ; CHECK-NEXT:    [[BUF_SROA_0_HWASAN:%.*]] = inttoptr i64 [[TMP9]] to ptr
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0(i64 16, ptr nonnull [[BUF_SROA_0]])
 ; CHECK-NEXT:    [[TMP10:%.*]] = trunc i64 [[TMP5]] to i8
 ; CHECK-NEXT:    call void @__hwasan_tag_memory(ptr [[BUF_SROA_0]], i8 [[TMP10]], i64 16)
 ; CHECK-NEXT:    [[TMP11:%.*]] = ptrtoint ptr [[BUF_SROA_0_HWASAN]] to i64
@@ -116,6 +117,7 @@
 ; CHECK-NEXT:    store volatile i8 0, ptr [[BUF_SROA_0_HWASAN]], align 4
 ; CHECK-NEXT:    [[TMP12:%.*]] = trunc i64 [[HWASAN_UAR_TAG]] to i8
 ; CHECK-NEXT:    call void @__hwasan_tag_memory(ptr [[BUF_SROA_0]], i8 [[TMP12]], i64 16)
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0(i64 16, ptr nonnull [[BUF_SROA_0]])
 ; CHECK-NEXT:    ret i32 0
 ;
 ; INLINE-LABEL: define i32 @test_simple
@@ -148,6 +150,7 @@
 ; INLINE-NEXT:    [[TMP19:%.*]] = shl i64 [[TMP16]], 57
 ; INLINE-NEXT:    [[TMP20:%.*]] = or i64 [[TMP18]], [[TMP19]]
 ; INLINE-NEXT:    [[BUF_SROA_0_HWASAN:%.*]] = inttoptr i64 [[TMP20]] to ptr
+; INLINE-NEXT:    call void @llvm.lifetime.start.p0(i64 16, ptr nonnull [[BUF_SROA_0]])
 ; INLINE-NEXT:    [[TMP21:%.*]] = trunc i64 [[TMP16]] to i8
 ; INLINE-NEXT:    [[TMP22:%.*]] = ptrtoint ptr [[BUF_SROA_0]] to i64
 ; INLINE-NEXT:    [[TMP23:%.*]] = and i64 [[TMP22]], -9079256848778919937
@@ -194,6 +197,7 @@
 ; INLINE-NEXT:    [[TMP54:%.*]] = lshr i64 [[TMP53]], 4
 ; INLINE-NEXT:    [[TMP55:%.*]] = getelementptr i8, ptr [[TMP14]], i64 [[TMP54]]
 ; INLINE-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[TMP55]], i8 [[TMP51]], i64 1, i1 false)
+; INLINE-NEXT:    call void @llvm.lifetime.end.p0(i64 16, ptr nonnull [[BUF_SROA_0]])
 ; INLINE-NEXT:    ret i32 0
 ;
 entry: