diff --git a/CMakeLists.txt b/CMakeLists.txt
index ae939a9..e07a06d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -72,6 +72,8 @@ if(NOT MSVC)
    target_compile_options(snmalloc_lib INTERFACE -mcx16)
   elseif(${CMAKE_SYSTEM_PROCESSOR} STREQUAL "amd64")
    target_compile_options(snmalloc_lib INTERFACE -mcx16)
+  elseif(${CMAKE_SYSTEM_PROCESSOR} STREQUAL "AMD64")
+   target_compile_options(snmalloc_lib INTERFACE -mcx16)
   elseif(${CMAKE_SYSTEM_PROCESSOR} STREQUAL "x86")
    target_compile_options(snmalloc_lib INTERFACE -mcx16)
   # XXX elseif ARM?
diff --git a/src/ds/bits.h b/src/ds/bits.h
index f519071..a7a791f 100644
--- a/src/ds/bits.h
+++ b/src/ds/bits.h
@@ -13,7 +13,9 @@
 #include <cassert>
 #include <cstdint>
 #include <type_traits>
-
+#if defined(_WIN32) && defined(__GNUC__)
+#define USE_CLZLL
+#endif
 #ifdef pause
 #  undef pause
 #endif
@@ -75,6 +77,8 @@ namespace snmalloc
 
       return BITS - index - 1;
 #  endif
+#elif defined(USE_CLZLL)
+      return static_cast<size_t>(__builtin_clzll(x));
 #else
       return static_cast<size_t>(__builtin_clzl(x));
 #endif
diff --git a/src/pal/pal_windows.h b/src/pal/pal_windows.h
index 0f3b608..8c1fc27 100644
--- a/src/pal/pal_windows.h
+++ b/src/pal/pal_windows.h
@@ -5,8 +5,13 @@
 #include "../mem/allocconfig.h"
 
 #ifdef _WIN32
+#  ifndef _MSC_VER
+#    include <cstdio>
+#  endif
 #  define WIN32_LEAN_AND_MEAN
-#  define NOMINMAX
+#  ifndef NOMINMAX
+#    define NOMINMAX
+#  endif
 #  include <windows.h>
 // VirtualAlloc2 is exposed in RS5 headers.
 #  ifdef NTDDI_WIN10_RS5
diff --git a/src/test/usage.h b/src/test/usage.h
index c48a631..5cc290a 100644
--- a/src/test/usage.h
+++ b/src/test/usage.h
@@ -2,7 +2,9 @@
 
 #if defined(_WIN32)
 #  define WIN32_LEAN_AND_MEAN
-#  define NOMINMAX
+#  ifndef NOMINMAX
+#    define NOMINMAX
+#  endif
 #  include <windows.h>
 // Needs to be included after windows.h
 #  include <psapi.h>