Reland "Integrate SIMD optimisations for zlib"

third_party/zlib/x86.c

+/*
+ * x86 feature check
+ *
+ * Copyright (C) 2013 Intel Corporation. All rights reserved.
+ * Author:
+ *  Jim Kukunas
+ * 
+ * For conditions of distribution and use, see copyright notice in zlib.h
+ */
+
+#include "x86.h"
+
+int x86_cpu_enable_simd;
+
+#ifndef _MSC_VER
+#include <pthread.h>
+
+pthread_once_t cpu_check_inited_once = PTHREAD_ONCE_INIT;
+static void _x86_check_features(void);
+
+void x86_check_features(void)
+{
+  pthread_once(&cpu_check_inited_once, _x86_check_features);
+}
+
+static void _x86_check_features(void)
+{
+    int x86_cpu_has_sse2;
+    int x86_cpu_has_sse42;
+    int x86_cpu_has_pclmulqdq;
+    unsigned eax, ebx, ecx, edx;
+
+    eax = 1;
+#ifdef __i386__
+    __asm__ __volatile__ (
+        "xchg %%ebx, %1\n\t"
+        "cpuid\n\t"
+        "xchg %1, %%ebx\n\t"
+    : "+a" (eax), "=S" (ebx), "=c" (ecx), "=d" (edx)
+    );
+#else
+    __asm__ __volatile__ (
+        "cpuid\n\t"
+    : "+a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx)
+    );
+#endif  /* (__i386__) */
+
+    x86_cpu_has_sse2 = edx & 0x4000000;
+    x86_cpu_has_sse42 = ecx & 0x100000;
+    x86_cpu_has_pclmulqdq = ecx & 0x2;
+
+    x86_cpu_enable_simd = x86_cpu_has_sse2 &&
+                          x86_cpu_has_sse42 &&
+                          x86_cpu_has_pclmulqdq;
+}
+#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));
+
+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;
+}
+
+static void _x86_check_features(void)
+{
+    int x86_cpu_has_sse2;
+    int x86_cpu_has_sse42;
+    int x86_cpu_has_pclmulqdq;
+    int regs[4];
+
+    __cpuid(regs, 1);
+
+    x86_cpu_has_sse2 = regs[3] & 0x4000000;
+    x86_cpu_has_sse42= regs[2] & 0x100000;
+    x86_cpu_has_pclmulqdq = regs[2] & 0x2;
+
+    x86_cpu_enable_simd = x86_cpu_has_sse2 &&
+                          x86_cpu_has_sse42 &&
+                          x86_cpu_has_pclmulqdq;
+}
+#endif  /* _MSC_VER */