Index: compiler-rt/CMakeLists.txt
===================================================================
--- compiler-rt/CMakeLists.txt
+++ compiler-rt/CMakeLists.txt
@@ -43,6 +43,25 @@
 option(COMPILER_RT_BUILD_XRAY_NO_PREINIT "Build xray with no preinit patching" OFF)
 mark_as_advanced(COMPILER_RT_BUILD_XRAY_NO_PREINIT)
 
+set(COMPILER_RT_ASAN_SHADOW_SCALE ""
+    CACHE STRING "Override the shadow scale to be used in ASan runtime")
+
+if (NOT COMPILER_RT_ASAN_SHADOW_SCALE STREQUAL "")
+  # Check that the shadow scale value is valid.
+  if (NOT (COMPILER_RT_ASAN_SHADOW_SCALE GREATER -1 AND
+           COMPILER_RT_ASAN_SHADOW_SCALE LESS 8))
+    message(FATAL_ERROR "
+      Invalid ASan Shadow Scale '${COMPILER_RT_ASAN_SHADOW_SCALE}'.")
+  endif()
+
+  set(COMPILER_RT_ASAN_SHADOW_SCALE_LLVM_FLAG
+      -mllvm -asan-mapping-scale -mllvm "${COMPILER_RT_ASAN_SHADOW_SCALE}")
+  set(COMPILER_RT_ASAN_SHADOW_SCALE_DEFINITION
+      "ASAN_SHADOW_SCALE=${COMPILER_RT_ASAN_SHADOW_SCALE}")
+  set(COMPILER_RT_ASAN_SHADOW_SCALE_FLAG
+      "-D${COMPILER_RT_ASAN_SHADOW_SCALE_DEFINITION}")
+endif()
+
 set(COMPILER_RT_BAREMETAL_BUILD OFF CACHE BOOLEAN
   "Build for a bare-metal target.")
 
Index: compiler-rt/lib/asan/CMakeLists.txt
===================================================================
--- compiler-rt/lib/asan/CMakeLists.txt
+++ compiler-rt/lib/asan/CMakeLists.txt
@@ -39,6 +39,7 @@
 include_directories(..)
 
 set(ASAN_CFLAGS ${SANITIZER_COMMON_CFLAGS})
+set(ASAN_COMMON_DEFINITIONS ${COMPILER_RT_ASAN_SHADOW_SCALE_DEFINITION})
 
 append_rtti_flag(OFF ASAN_CFLAGS)
 
Index: compiler-rt/lib/asan/asan_mapping.h
===================================================================
--- compiler-rt/lib/asan/asan_mapping.h
+++ compiler-rt/lib/asan/asan_mapping.h
@@ -131,7 +131,11 @@
 // || `[0x30000000, 0x35ffffff]` || LowShadow  ||
 // || `[0x00000000, 0x2fffffff]` || LowMem     ||
 
+#if defined(ASAN_SHADOW_SCALE)
+static const u64 kDefaultShadowScale = ASAN_SHADOW_SCALE;
+#else
 static const u64 kDefaultShadowScale = 3;
+#endif
 static const u64 kDefaultShadowSentinel = ~(uptr)0;
 static const u64 kDefaultShadowOffset32 = 1ULL << 29;  // 0x20000000
 static const u64 kDefaultShadowOffset64 = 1ULL << 44;
Index: compiler-rt/lib/asan/tests/CMakeLists.txt
===================================================================
--- compiler-rt/lib/asan/tests/CMakeLists.txt
+++ compiler-rt/lib/asan/tests/CMakeLists.txt
@@ -23,6 +23,7 @@
 set(ASAN_UNITTEST_COMMON_CFLAGS
   ${COMPILER_RT_UNITTEST_CFLAGS}
   ${COMPILER_RT_GTEST_CFLAGS}
+  ${COMPILER_RT_ASAN_SHADOW_SCALE_LLVM_FLAG}
   -I${COMPILER_RT_SOURCE_DIR}/include
   -I${COMPILER_RT_SOURCE_DIR}/lib
   -I${COMPILER_RT_SOURCE_DIR}/lib/asan
@@ -52,6 +53,7 @@
 
 # Use -D instead of definitions to please custom compile command.
 list(APPEND ASAN_UNITTEST_COMMON_CFLAGS
+  ${COMPILER_RT_ASAN_SHADOW_SCALE_FLAG}
   -DASAN_HAS_BLACKLIST=1
   -DASAN_HAS_EXCEPTIONS=1
   -DASAN_UAR=0)
Index: compiler-rt/test/asan/lit.cfg
===================================================================
--- compiler-rt/test/asan/lit.cfg
+++ compiler-rt/test/asan/lit.cfg
@@ -65,8 +65,8 @@
 # FIXME: Review the set of required flags and check if it can be reduced.
 target_cflags = [get_required_attr(config, "target_cflags")] + extra_link_flags
 target_cxxflags = config.cxx_mode_flags + target_cflags
-clang_asan_static_cflags = (["-fsanitize=address",
-                            "-mno-omit-leaf-frame-pointer",
+clang_asan_static_cflags = (config.sanitize_address_cflags +
+                            ["-mno-omit-leaf-frame-pointer",
                             "-fno-omit-frame-pointer",
                             "-fno-optimize-sibling-calls"] +
                             config.debug_info_flags + target_cflags)
Index: compiler-rt/test/lit.common.cfg
===================================================================
--- compiler-rt/test/lit.common.cfg
+++ compiler-rt/test/lit.common.cfg
@@ -51,6 +51,12 @@
 # Add compiler ID to the list of available features.
 config.available_features.add(compiler_id)
 
+# Set cflags required for -fsanitize=address.
+config.sanitize_address_cflags = ["-fsanitize=address"]
+if config.asan_shadow_scale != '':
+  config.sanitize_address_cflags += ["-mllvm", "-asan-mapping-scale",
+                                     "-mllvm", config.asan_shadow_scale]
+
 # BFD linker in 64-bit android toolchains fails to find libm.so, which is a
 # transitive shared library dependency (via asan runtime).
 if config.android:
Index: compiler-rt/test/lit.common.configured.in
===================================================================
--- compiler-rt/test/lit.common.configured.in
+++ compiler-rt/test/lit.common.configured.in
@@ -25,6 +25,7 @@
 set_default("compiler_rt_debug", @COMPILER_RT_DEBUG_PYBOOL@)
 set_default("compiler_rt_libdir", "@COMPILER_RT_LIBRARY_OUTPUT_DIR@")
 set_default("emulator", "@COMPILER_RT_EMULATOR@")
+set_default("asan_shadow_scale", "@COMPILER_RT_ASAN_SHADOW_SCALE@")
 set_default("ios", False)
 set_default("iossim", False)
 set_default("sanitizer_can_use_cxxabi", @SANITIZER_CAN_USE_CXXABI_PYBOOL@)
Index: compiler-rt/test/lsan/lit.common.cfg
===================================================================
--- compiler-rt/test/lsan/lit.common.cfg
+++ compiler-rt/test/lsan/lit.common.cfg
@@ -26,7 +26,7 @@
   lsan_cflags = ["-fsanitize=leak"]
 elif lsan_lit_test_mode == "AddressSanitizer":
   config.name = "LeakSanitizer-AddressSanitizer"
-  lsan_cflags = ["-fsanitize=address"]
+  lsan_cflags = config.sanitize_address_cflags
   config.available_features.add('asan')
 else:
   lit_config.fatal("Unknown LSan test mode: %r" % lsan_lit_test_mode)
Index: compiler-rt/test/sanitizer_common/lit.common.cfg
===================================================================
--- compiler-rt/test/sanitizer_common/lit.common.cfg
+++ compiler-rt/test/sanitizer_common/lit.common.cfg
@@ -7,7 +7,7 @@
 
 default_tool_options = []
 if config.tool_name == "asan":
-  tool_cflags = ["-fsanitize=address"]
+  tool_cflags = config.sanitize_address_cflags
   tool_options = "ASAN_OPTIONS"
 elif config.tool_name == "tsan":
   tool_cflags = ["-fsanitize=thread"]
Index: compiler-rt/test/ubsan/lit.common.cfg
===================================================================
--- compiler-rt/test/ubsan/lit.common.cfg
+++ compiler-rt/test/ubsan/lit.common.cfg
@@ -28,7 +28,7 @@
 elif ubsan_lit_test_mode == "AddressSanitizer":
   config.name = 'UBSan-ASan-' + config.target_arch
   config.available_features.add("ubsan-asan")
-  clang_ubsan_cflags = ["-fsanitize=address"]
+  clang_ubsan_cflags = config.sanitize_address_cflags
   default_ubsan_opts += ['detect_leaks=0']
 elif ubsan_lit_test_mode == "MemorySanitizer":
   config.name = 'UBSan-MSan-' + config.target_arch