Index: lib/asan/asan_rtl.cc
===================================================================
--- lib/asan/asan_rtl.cc
+++ lib/asan/asan_rtl.cc
@@ -37,7 +37,10 @@
 
 namespace __asan {
 
+const unsigned kAsanBuggyPcPoolSize = 25;
+
 uptr AsanMappingProfile[kAsanMappingProfileSize];
+uptr AsanBuggyPcPool[kAsanBuggyPcPoolSize];
 
 static void AsanDie() {
   static atomic_uint32_t num_calls;
@@ -107,6 +110,27 @@
   PoisonShadow(ptr, size, kAsanInternalHeapMagic);
 }
 
+// -------------- SuppressErrorReport -------------- {{{1
+// We need to avoid error reports duplicating for ASan recover mode.
+static bool SuppressErrorReport(uptr pc) {
+  if (!common_flags()->suppress_equal_pcs) return false;
+  static __sanitizer::atomic_uint32_t pc_num_atomic;
+  u32 pc_num = atomic_fetch_add(&pc_num_atomic, 1, memory_order_acquire);
+  // We have exceeded reasonable number of different reports, subsequent
+  // errors are likely artificial, so die here.
+  if (pc_num >= kAsanBuggyPcPoolSize)
+    Die();
+
+  for (int i = pc_num; i >= 0; --i)
+    if (pc == AsanBuggyPcPool[i]) return true;
+
+  // Race here, because some other thread may increase pc_num. This would lead
+  // to some pool entries would contain zeroes. This is OK, because we don't
+  // need exact presicion. Don't use atomic write due to performance issue.
+  AsanBuggyPcPool[pc_num] = pc;
+  return false;
+}
+
 // -------------------------- Run-time entry ------------------- {{{1
 // exported functions
 #define ASAN_REPORT_ERROR(type, is_write, size)                     \
@@ -123,6 +147,7 @@
 extern "C" NOINLINE INTERFACE_ATTRIBUTE                             \
 void __asan_report_ ## type ## size ## _noabort(uptr addr) {        \
   GET_CALLER_PC_BP_SP;                                              \
+  if (SuppressErrorReport(pc)) return;                              \
   ReportGenericError(pc, bp, sp, addr, is_write, size, 0, false);   \
 }                                                                   \
 
@@ -151,6 +176,7 @@
 extern "C" NOINLINE INTERFACE_ATTRIBUTE                                     \
 void __asan_report_ ## type ## _n_noabort(uptr addr, uptr size) {           \
   GET_CALLER_PC_BP_SP;                                                      \
+  if (SuppressErrorReport(pc)) return;                                      \
   ReportGenericError(pc, bp, sp, addr, is_write, size, 0, false);           \
 }                                                                           \
 
@@ -169,6 +195,7 @@
           *__asan_test_only_reported_buggy_pointer = addr;                     \
         } else {                                                               \
           GET_CALLER_PC_BP_SP;                                                 \
+          if (SuppressErrorReport(pc)) return;                                 \
           ReportGenericError(pc, bp, sp, addr, is_write, size, exp_arg,        \
                               fatal);                                          \
         }                                                                      \
@@ -223,6 +250,7 @@
 void __asan_loadN_noabort(uptr addr, uptr size) {
   if (__asan_region_is_poisoned(addr, size)) {
     GET_CALLER_PC_BP_SP;
+    if (SuppressErrorReport(pc)) return;
     ReportGenericError(pc, bp, sp, addr, false, size, 0, false);
   }
 }
@@ -250,6 +278,7 @@
 void __asan_storeN_noabort(uptr addr, uptr size) {
   if (__asan_region_is_poisoned(addr, size)) {
     GET_CALLER_PC_BP_SP;
+    if (SuppressErrorReport(pc)) return;
     ReportGenericError(pc, bp, sp, addr, true, size, 0, false);
   }
 }
Index: lib/sanitizer_common/sanitizer_flags.inc
===================================================================
--- lib/sanitizer_common/sanitizer_flags.inc
+++ lib/sanitizer_common/sanitizer_flags.inc
@@ -192,3 +192,6 @@
     bool, abort_on_error, SANITIZER_MAC,
     "If set, the tool calls abort() instead of _exit() after printing the "
     "error report.")
+COMMON_FLAG(bool, suppress_equal_pcs, true,
+            "Deduplicate multiple reports for single source location in "
+            "halt_on_error = false mode.")
Index: test/asan/TestCases/Posix/halt_on_error-signals.c
===================================================================
--- test/asan/TestCases/Posix/halt_on_error-signals.c
+++ test/asan/TestCases/Posix/halt_on_error-signals.c
@@ -3,7 +3,7 @@
 // RUN: %clang_asan -fsanitize-recover=address -pthread %s -o %t
 //
 // RUN: rm -f %t.log
-// RUN: %env_asan_opts=halt_on_error=false %run %t 100 >%t.log 2>&1 || true
+// RUN: %env_asan_opts=halt_on_error=false:suppress_equal_pcs=false %run %t 100 >%t.log 2>&1 || true
 // Collision will almost always get triggered but we still need to check the unlikely case:
 // RUN: FileCheck --check-prefix=CHECK-COLLISION %s < %t.log || FileCheck --check-prefix=CHECK-NO-COLLISION %s < %t.log
 
Index: test/asan/TestCases/Posix/halt_on_error-torture.cc
===================================================================
--- test/asan/TestCases/Posix/halt_on_error-torture.cc
+++ test/asan/TestCases/Posix/halt_on_error-torture.cc
@@ -2,13 +2,13 @@
 //
 // RUN: %clangxx_asan -fsanitize-recover=address -pthread %s -o %t
 //
-// RUN: %env_asan_opts=halt_on_error=false %run %t 1 10 >1.txt 2>&1
+// RUN: %env_asan_opts=halt_on_error=false:suppress_equal_pcs=false %run %t 1 10 >1.txt 2>&1
 // RUN: FileCheck %s < 1.txt
 // RUN: [ $(grep -c 'ERROR: AddressSanitizer: use-after-poison' 1.txt) -eq 10 ]
 // RUN: FileCheck --check-prefix=CHECK-NO-COLLISION %s < 1.txt
 //
 // Collisions are unlikely but still possible so we need the ||.
-// RUN: %env_asan_opts=halt_on_error=false %run %t 10 20 >10.txt 2>&1 || true
+// RUN: %env_asan_opts=halt_on_error=false ASAN_SUPPRESS_EQUAL_PCS=0 %run %t 10 20 >10.txt 2>&1 || true
 // This one is racy although _very_ unlikely to fail:
 // RUN: FileCheck %s < 10.txt
 // RUN: FileCheck --check-prefix=CHECK-COLLISION %s < 1.txt || FileCheck --check-prefix=CHECK-NO-COLLISION %s < 1.txt
Index: test/asan/TestCases/halt_on_error-2.c
===================================================================
--- /dev/null
+++ test/asan/TestCases/halt_on_error-2.c
@@ -0,0 +1,22 @@
+// Test reports dedupication for recovery mode.
+//
+// RUN: %clang_asan -fsanitize-recover=address %s -o %t
+// RUN: %env_asan_opts=halt_on_error=false not %run %t 2>&1
+
+volatile int ten = 10;
+unsigned kNumIterations = 10;
+
+int main() {
+  char x[10];
+  for (int i = 0; i < kNumIterations; ++i) {
+    // CHECK: READ of size 1
+    volatile int res = x[ten + i];
+    // CHECK: WRITE of size 1
+     x[i + ten] = res + 3;
+    // CHECK: READ of size 1
+     res = x[ten + i];
+    // CHECK-NOT: READ of size 1
+    // CHECK-NOT: WRITE of size 1
+  }
+  return  0;
+}
Index: test/asan/TestCases/halt_on_error-3.c
===================================================================
--- /dev/null
+++ test/asan/TestCases/halt_on_error-3.c
@@ -0,0 +1,30 @@
+// Test reports dedupication for recovery mode.
+//
+// RUN: %clang_asan -fsanitize-recover=address %s -o %t
+// RUN: %env_asan_opts=halt_on_error=false %run %t >3.txt 2>&1 || true
+// RUN: [ $(grep -c 'ERROR: AddressSanitizer: stack-buffer-overflow' 3.txt) -eq 25 ]
+
+#define ACCESS_ARRAY_FIVE_ELEMENTS(array, i)     \
+  array[i] = i;                                  \
+  array[i + 1] = i + 1;                          \
+  array[i + 2] = i + 2;                          \
+  array[i + 3] = i + 3;                          \
+  array[i + 4] = i + 4;                          \
+
+volatile int ten = 10;
+unsigned kNumIterations = 10;
+
+int main() {
+  char a[10];
+  char b[10];
+  for (int i = 0; i < kNumIterations; ++i) {
+    ACCESS_ARRAY_FIVE_ELEMENTS(a, ten);
+    ACCESS_ARRAY_FIVE_ELEMENTS(a, ten + 5);
+    ACCESS_ARRAY_FIVE_ELEMENTS(a, ten + 10);
+    ACCESS_ARRAY_FIVE_ELEMENTS(b, ten);
+    ACCESS_ARRAY_FIVE_ELEMENTS(b, ten + 5);
+    ACCESS_ARRAY_FIVE_ELEMENTS(b, ten + 10);
+  }
+  return 0;
+}
+