CPUID improvements

- Make ws_cpuid() return boolean when CPUID is support or no, this way
it's easier for caller to determinate if it works (and can use cpuinfo[X] or no).

- Add function ws_cpuid_sse42(), use it in ws_mempbrk() [cached] &
  version information.

Change-Id: I4e77699f9f3d11bb9b2e8ea599e48d3c5ad84ed7
Reviewed-on: https://code.wireshark.org/review/2088
Reviewed-by: Anders Broman <a.broman58@gmail.com>

version_info.c

@@ -629,7 +629,8 @@ static void get_cpu_info(GString *str _U_)
 
 	/* Calling __cpuid with 0x80000000 as the InfoType argument*/
 	/* gets the number of valid extended IDs.*/
-	ws_cpuid(CPUInfo, 0x80000000);
+	if (!ws_cpuid(CPUInfo, 0x80000000))
+		return;
 	nExIds = CPUInfo[0];
 
 	if( nExIds<0x80000005)
@@ -646,6 +647,8 @@ static void get_cpu_info(GString *str _U_)
 
 	g_string_append_printf(str, "\n%s", CPUBrandString);
 
+	if (ws_cpuid_sse42())
+		g_string_append(str, " (with SSE4.2)");
 }
 
 static void get_mem_info(GString *str _U_)

wsutil/ws_cpuid.h

@@ -23,20 +23,23 @@
 /*
  * Get CPU info on platforms where the cpuid instruction can be used skip 32 bit versions for GCC
  * 	http://www.intel.com/content/dam/www/public/us/en/documents/application-notes/processor-identification-cpuid-instruction-note.pdf
- * the ws_cpuid() routine will return 0 in CPUInfo[0] if cpuinfo isn't available.
+ * the ws_cpuid() routine will return 0 if cpuinfo isn't available.
  */
 
 #if defined(_MSC_VER)     /* MSVC */
-static void
+static int
 ws_cpuid(guint32 *CPUInfo, guint32 selector)
 {
+	CPUInfo[0] = CPUInfo[1] = CPUInfo[2] = CPUInfo[3] = 0;
 	__cpuid((int *) CPUInfo, selector);
+	/* XXX, how to check if it's supported on MSVC? just in case clear all flags above */
+	return 1;
 }
 
 #elif defined(__GNUC__)  /* GCC/clang */
 
 #if defined(__x86_64__)
-static inline void
+static inline int
 ws_cpuid(guint32 *CPUInfo, int selector)
 {
 	__asm__ __volatile__("cpuid"
@@ -45,22 +48,35 @@ ws_cpuid(guint32 *CPUInfo, int selector)
 							"=c" (CPUInfo[2]),
 							"=d" (CPUInfo[3])
 						: "a"(selector));
+	return 1;
 }
 #else /* (__i386__) */
 
-static void
+static int
 ws_cpuid(guint32 *CPUInfo, int selector _U_)
 {
 	/* TODO: need a test if older proccesors have the cpuid instruction */
-	CPUInfo[0] = 0;
+	return 0;
 }
 #endif
 
 #else /* Other compilers */
 
-static void
+static int
 ws_cpuid(guint32 *CPUInfo, int selector _U_)
 {
-	CPUInfo[0] = 0;
+	return 0;
 }
 #endif
+
+static int
+ws_cpuid_sse42(void)
+{
+	guint32 CPUInfo[4];
+
+	if (!ws_cpuid(CPUInfo, 1))
+		return 0;
+
+	/* in ECX bit 20 toggled on */
+	return (CPUInfo[2] & (1 << 20));
+}

wsutil/ws_mempbrk.c

@@ -51,19 +51,16 @@ WS_DLL_PUBLIC const guint8 *
 ws_mempbrk(const guint8* haystack, size_t haystacklen, const guint8 *needles)
 {
 #ifdef HAVE_SSE42
-	guint32 CPUInfo[4];
-	guint32 bSSE42Extensions;
-
+	static int have_sse42 = -1;
 #endif
 	if (*needles == 0)
 		return NULL;
 
 #ifdef HAVE_SSE42
-	ws_cpuid(CPUInfo, 1);
+	if G_UNLIKELY(have_sse42 < 0)
+		have_sse42 = ws_cpuid_sse42();
 
-	bSSE42Extensions = (CPUInfo[2] & 0x100000);
-
-	if (haystacklen >= 16 && bSSE42Extensions)
+	if (haystacklen >= 16 && have_sse42)
 		return _ws_mempbrk_sse42(haystack, haystacklen, needles);
 #endif