zlib: Remove Windows XP workaround for CPU feature detection

third_party/zlib/x86.c

Index: third_party/zlib/x86.c
diff --git a/third_party/zlib/x86.c b/third_party/zlib/x86.c
index 0649306f2f0ffd39bd26bd31346919593cffa55c..e6532fd10ddb46fd0305287d158cc888fc6faa8c 100644
--- a/third_party/zlib/x86.c
+++ b/third_party/zlib/x86.c
@@ -56,43 +56,21 @@ static void _x86_check_features(void)
 #else
 #include <intrin.h>
 #include <windows.h>
-#include <stdint.h>
 
-static volatile int32_t once_control = 0;
-static void _x86_check_features(void);
-static int fake_pthread_once(volatile int32_t *once_control,
-                             void (*init_routine)(void));
+static BOOL CALLBACK _x86_check_features(PINIT_ONCE once,
+                                         PVOID param,
+                                         PVOID *context);
+static INIT_ONCE cpu_check_inited_once = INIT_ONCE_STATIC_INIT;
 
 void x86_check_features(void)
 {
-    fake_pthread_once(&once_control, _x86_check_features);
-}
-
-/* Copied from "perftools_pthread_once" in tcmalloc */
-static int fake_pthread_once(volatile int32_t *once_control,
-                             void (*init_routine)(void)) {
-    // Try for a fast path first. Note: this should be an acquire semantics read
-    // It is on x86 and x64, where Windows runs.
-    if (*once_control != 1) {
-        while (1) {
-            switch (InterlockedCompareExchange(once_control, 2, 0)) {
-                case 0:
-                    init_routine();
-                    InterlockedExchange(once_control, 1);
-                    return 0;
-                case 1:
-                    // The initializer has already been executed
-                    return 0;
-                default:
-                    // The initializer is being processed by another thread
-                    SwitchToThread();
-            }
-        }
-    }
-    return 0;
+    InitOnceExecuteOnce(&cpu_check_inited_once, _x86_check_features,
+                        NULL, NULL);
 }
 
-static void _x86_check_features(void)
+static BOOL CALLBACK _x86_check_features(PINIT_ONCE once,
+                                         PVOID param,
+                                         PVOID *context)
 {
     int x86_cpu_has_sse2;
     int x86_cpu_has_sse42;
@@ -108,5 +86,6 @@ static void _x86_check_features(void)
     x86_cpu_enable_simd = x86_cpu_has_sse2 &&
                           x86_cpu_has_sse42 &&
                           x86_cpu_has_pclmulqdq;
+    return TRUE;
 }
 #endif  /* _MSC_VER */