Translate cpu detection from assembly to C++

code/getcpu.cpp

@@ -43,17 +43,7 @@
 #include <cstdio>
 #include <cstring>
 
-/*
-**	Prototypes for linkage to assembly module
-*/
-extern "C" {
-	bool __cdecl Detect_MMX_Availability (void);
-	bool __cdecl Detect_CMOV_Availability (void);
-
-	extern char CPUType;
-	extern char VendorID;
-}
-
+#include <intrin.h>
 
 /***********************************************************************************************
  * Get_CPU_Type -- Find out what kind of CPU we are running on                                 *
@@ -72,21 +62,71 @@ extern "C" {
  * HISTORY:                                                                                    *
  *    6/26/96 10:15AM ST : Created                                                             *
  *=============================================================================================*/
+
+extern "C" {
+
+char UseCMOV = 1;
+char HasCMOV = 1;
+char UseMMX = 1;
+char CPUType = 0;
+
+/*
+ * Filled in by Detect_MMX_Availability from CPUID leaf 0. The buffer holds the twelve
+ * vendor characters, the separating space the original wrote after them, and the
+ * terminator Get_CPU_Type copies up to.
+ */
+char VendorID[20] = "Not available";
+
+}
+
+
+/// <summary>
+/// Records the processor family in CPUType and the vendor in VendorID, and reports MMX
+/// support. The supported minimum hardware (SSE2, so a Pentium 4 or Athlon 64 onward) always
+/// has MMX, so this always sets UseMMX and returns true rather than reading the CPUID
+/// feature bit.
+/// </summary>
+/// <returns>bool; always true on the supported minimum hardware.</returns>
+bool __cdecl Detect_MMX_Availability(void)
+{
+	int regs[4];
+
+	char cputype = 4;
+
+	__cpuid(regs, 0);
+	int const maxleaf = regs[0];
+
+	std::memcpy(&VendorID[0], &regs[1], 4);
+	std::memcpy(&VendorID[4], &regs[3], 4);
+	std::memcpy(&VendorID[8], &regs[2], 4);
+	VendorID[12] = ' ';
+	VendorID[13] = '\0';
+
+	if (maxleaf >= 1) {
+		__cpuid(regs, 1);
+		cputype = (char)((regs[0] & 0x0F00) >> 8);
+	}
+
+	CPUType = cputype;
+
+	UseMMX = 1;
+	return(true);
+}
+
+
 void Get_CPU_Type(int & cpu_type, bool & mmx, char * vendor_id, int vendor_id_length)
 {
 	/*
 	**	Call the asm CPU detection code
 	*/
 	mmx = Detect_MMX_Availability();
-	Detect_CMOV_Availability();
 
 	/*
 	**	Return the promised results
 	*/
 	cpu_type = (int)CPUType;
 
 	if (vendor_id != NULL) {
-		char * vendor_ptr = &VendorID;
-		strncpy(vendor_id, vendor_ptr, vendor_id_length);
+		strncpy(vendor_id, VendorID, vendor_id_length);
 	}
 }