Index: compiler-rt/trunk/cmake/config-ix.cmake
===================================================================
--- compiler-rt/trunk/cmake/config-ix.cmake
+++ compiler-rt/trunk/cmake/config-ix.cmake
@@ -317,13 +317,13 @@
 
   # We're setting the flag manually for each target OS
   set(CMAKE_OSX_DEPLOYMENT_TARGET "")
-  
+
   set(DARWIN_COMMON_CFLAGS -stdlib=libc++)
   set(DARWIN_COMMON_LINK_FLAGS
     -stdlib=libc++
     -lc++
     -lc++abi)
-  
+
   check_linker_flag("-fapplication-extension" COMPILER_RT_HAS_APP_EXTENSION)
   if(COMPILER_RT_HAS_APP_EXTENSION)
     list(APPEND DARWIN_COMMON_LINK_FLAGS "-fapplication-extension")
@@ -344,7 +344,7 @@
   # Figure out which arches to use for each OS
   darwin_get_toolchain_supported_archs(toolchain_arches)
   message(STATUS "Toolchain supported arches: ${toolchain_arches}")
-  
+
   if(NOT MACOSX_VERSION_MIN_FLAG)
     darwin_test_archs(osx
       DARWIN_osx_ARCHS
@@ -648,10 +648,7 @@
 endif()
 
 if (COMPILER_RT_HAS_SANITIZER_COMMON AND FUZZER_SUPPORTED_ARCH AND
-    OS_NAME MATCHES "Android|Darwin|Linux|NetBSD|FreeBSD|OpenBSD|Fuchsia|Windows" AND
-    # TODO: Support builds with MSVC.
-    NOT "${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC" AND
-    NOT "${CMAKE_C_COMPILER_ID}" STREQUAL "MSVC")
+    OS_NAME MATCHES "Android|Darwin|Linux|NetBSD|FreeBSD|OpenBSD|Fuchsia|Windows")
   set(COMPILER_RT_HAS_FUZZER TRUE)
 else()
   set(COMPILER_RT_HAS_FUZZER FALSE)
Index: compiler-rt/trunk/lib/fuzzer/CMakeLists.txt
===================================================================
--- compiler-rt/trunk/lib/fuzzer/CMakeLists.txt
+++ compiler-rt/trunk/lib/fuzzer/CMakeLists.txt
@@ -71,8 +71,14 @@
   list(APPEND LIBFUZZER_CFLAGS -fno-sanitize-coverage=trace-pc-guard,edge,trace-cmp,indirect-calls,8bit-counters)
 endif()
 
-if(NOT HAS_THREAD_LOCAL)
-  list(APPEND LIBFUZZER_CFLAGS -Dthread_local=__thread)
+if(OS_NAME MATCHES "Windows")
+  # Silence warnings with /Ehsc and avoid an error by unecessarily defining
+  # thread_local when it isn't even used on Windows.
+  list(APPEND LIBFUZZER_CFLAGS /EHsc)
+else()
+  if(NOT HAS_THREAD_LOCAL)
+    list(APPEND LIBFUZZER_CFLAGS -Dthread_local=__thread)
+  endif()
 endif()
 
 set(FUZZER_SUPPORTED_OS ${SANITIZER_COMMON_SUPPORTED_OS})
Index: compiler-rt/trunk/lib/fuzzer/FuzzerBuiltinsMsvc.h
===================================================================
--- compiler-rt/trunk/lib/fuzzer/FuzzerBuiltinsMsvc.h
+++ compiler-rt/trunk/lib/fuzzer/FuzzerBuiltinsMsvc.h
@@ -24,7 +24,7 @@
 
 // __builtin_return_address() cannot be compiled with MSVC. Use the equivalent
 // from <intrin.h>
-#define GET_CALLER_PC() reinterpret_cast<uintptr_t>(_ReturnAddress())
+#define GET_CALLER_PC() _ReturnAddress()
 
 namespace fuzzer {
 
Index: compiler-rt/trunk/lib/fuzzer/FuzzerSHA1.cpp
===================================================================
--- compiler-rt/trunk/lib/fuzzer/FuzzerSHA1.cpp
+++ compiler-rt/trunk/lib/fuzzer/FuzzerSHA1.cpp
@@ -31,7 +31,8 @@
 
 #ifdef __BIG_ENDIAN__
 # define SHA_BIG_ENDIAN
-#elif defined __LITTLE_ENDIAN__
+// Windows is always little endian and MSVC doesn't have <endian.h>
+#elif defined __LITTLE_ENDIAN__ || LIBFUZZER_WINDOWS
 /* override */
 #elif defined __BYTE_ORDER
 # if __BYTE_ORDER__ ==  __ORDER_BIG_ENDIAN__
Index: compiler-rt/trunk/lib/fuzzer/FuzzerValueBitMap.h
===================================================================
--- compiler-rt/trunk/lib/fuzzer/FuzzerValueBitMap.h
+++ compiler-rt/trunk/lib/fuzzer/FuzzerValueBitMap.h
@@ -34,7 +34,7 @@
     uintptr_t WordIdx = Idx / kBitsInWord;
     uintptr_t BitIdx = Idx % kBitsInWord;
     uintptr_t Old = Map[WordIdx];
-    uintptr_t New = Old | (1UL << BitIdx);
+    uintptr_t New = Old | (1ULL << BitIdx);
     Map[WordIdx] = New;
     return New != Old;
   }
@@ -48,7 +48,7 @@
     assert(Idx < kMapSizeInBits);
     uintptr_t WordIdx = Idx / kBitsInWord;
     uintptr_t BitIdx = Idx % kBitsInWord;
-    return Map[WordIdx] & (1UL << BitIdx);
+    return Map[WordIdx] & (1ULL << BitIdx);
   }
 
   size_t SizeInBits() const { return kMapSizeInBits; }