Index: compiler-rt/cmake/config-ix.cmake
===================================================================
--- compiler-rt/cmake/config-ix.cmake
+++ compiler-rt/cmake/config-ix.cmake
@@ -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/lib/fuzzer/CMakeLists.txt
===================================================================
--- compiler-rt/lib/fuzzer/CMakeLists.txt
+++ compiler-rt/lib/fuzzer/CMakeLists.txt
@@ -71,6 +71,10 @@
 
 if(NOT HAS_THREAD_LOCAL)
   list(APPEND LIBFUZZER_CFLAGS -Dthread_local=__thread)
+  # Needed to compile with MSVC.
+  if (OS_NAME MATCHES "Windows")
+    list(APPEND LIBFUZZER_CFLAGS -D_XKEYCHECK_H=1)
+  endif()
 endif()
 
 set(FUZZER_SUPPORTED_OS ${SANITIZER_COMMON_SUPPORTED_OS})
Index: compiler-rt/lib/fuzzer/FuzzerSHA1.cpp
===================================================================
--- compiler-rt/lib/fuzzer/FuzzerSHA1.cpp
+++ compiler-rt/lib/fuzzer/FuzzerSHA1.cpp
@@ -32,7 +32,9 @@
 
 #ifdef __BIG_ENDIAN__
 # define SHA_BIG_ENDIAN
-#elif defined __LITTLE_ENDIAN__
+// Added "|| LIBFUZZER_WINDOWS" for libFuzzer to compile with MSVC since it
+// doesn't have <endian.h> and Windows is always little endian.
+#elif defined __LITTLE_ENDIAN__ || LIBFUZZER_WINDOWS
 /* override */
 #elif defined __BYTE_ORDER
 # if __BYTE_ORDER__ ==  __ORDER_BIG_ENDIAN__
Index: compiler-rt/lib/fuzzer/FuzzerValueBitMap.h
===================================================================
--- compiler-rt/lib/fuzzer/FuzzerValueBitMap.h
+++ compiler-rt/lib/fuzzer/FuzzerValueBitMap.h
@@ -35,7 +35,7 @@
     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;
   }
@@ -49,7 +49,7 @@
     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; }