Index: lib/Transforms/Instrumentation/AddressSanitizer.cpp
===================================================================
--- lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -80,6 +80,7 @@
 static const uint64_t kAArch64_ShadowOffset64 = 1ULL << 36;
 static const uint64_t kFreeBSD_ShadowOffset32 = 1ULL << 30;
 static const uint64_t kFreeBSD_ShadowOffset64 = 1ULL << 46;
+static const uint64_t kFreeBSD_AArch64_ShadowOffset64 = 1ULL << 47;
 static const uint64_t kPS4CPU_ShadowOffset64 = 1ULL << 40;
 static const uint64_t kWindowsShadowOffset32 = 3ULL << 28;
 // The shadow memory space is dynamically allocated.
@@ -423,6 +424,8 @@
       Mapping.Offset = kPPC64_ShadowOffset64;
     else if (IsSystemZ)
       Mapping.Offset = kSystemZ_ShadowOffset64;
+    else if (IsFreeBSD && IsAArch64)
+      Mapping.Offset = kFreeBSD_AArch64_ShadowOffset64;
     else if (IsFreeBSD)
       Mapping.Offset = kFreeBSD_ShadowOffset64;
     else if (IsPS4CPU)
Index: test/Instrumentation/AddressSanitizer/freebsd.ll
===================================================================
--- test/Instrumentation/AddressSanitizer/freebsd.ll
+++ test/Instrumentation/AddressSanitizer/freebsd.ll
@@ -8,6 +8,11 @@
 ; RUN:     -data-layout="e-m:e-i64:64-f80:128-n8:16:32:64-S128" | \
 ; RUN:     FileCheck --check-prefix=CHECK-64 %s
 
+; RUN: opt < %s -asan -asan-module -S \
+; RUN:     -mtriple=aarch64-unknown-freebsd \
+; RUN:     -data-layout="e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128" | \
+; RUN:     FileCheck --check-prefix=CHECK-AARCH64 %s
+
 define i32 @read_4_bytes(i32* %a) sanitize_address {
 entry:
   %tmp1 = load i32, i32* %a, align 4
@@ -27,3 +32,10 @@
 ; CHECK-64: lshr {{.*}} 3
 ; CHECK-64-NEXT: {{70368744177664}}
 ; CHECK-64: ret
+
+; CHECK-AARCH64: @read_4_bytes
+; CHECK-AARCH64-NOT: ret
+; Check for ASAN's Offset for 64-bit (2^47 or 0x800000000000)
+; CHECK-AARCH64: lshr {{.*}} 3
+; CHECK-AARCH64-NEXT: {{140737488355328}}
+; CHECK-AARCH64: ret