Identify all cores and select the most performant one as TARGET

Author: martin-frbg

driver/others/dynamic_arm64.c

@@ -271,15 +271,52 @@ static gotoblas_t *get_coretype(void) {
 
   if (!(getauxval(AT_HWCAP) & HWCAP_CPUID)) {
 #ifdef __linux
+	int i;
+        int ncores=0;
+	int p,cpucap,cpulowperf=0,cpumidperf=0,cpuhiperf=0;
         FILE *infile;
         char buffer[512], *p, *cpu_part = NULL, *cpu_implementer = NULL;
         p = (char *) NULL ;
-	infile = fopen("/sys/devices/system/cpu/cpu0/regs/identification/midr_el1","r");
-	if (!infile) return NULL;
-	(void)fgets(buffer, sizeof(buffer), infile);
-	midr_el1=strtoul(buffer,NULL,16);
-	fclose(infile);
-#else
+	infile = fopen("/sys/devices/system/cpu/possible","r");
+	if (infile) {
+		(void)fgets(buffer, sizeof(buffer), infile);
+		sscanf(buffer,"0-%d",&ncores);
+		fclose (infile);
+		ncores++;
+	} else {
+		infile = fopen("/proc/cpuinfo","r");
+                while (fgets(buffer, sizeof(buffer), infile)) {
+                        if (!strncmp("processor", buffer, 9))
+                        ncores++;
+		}
+	}
+	for (i=0;i<ncores;i++) {
+		sprintf(buffer,"/sys/devices/system/cpu/cpu%d/regs/identification/midr_el1",i);
+		infile = fopen(buffer,"r");
+		if (!infile) return NULL;
+		(void)fgets(buffer, sizeof(buffer), infile);
+		midr_el1=strtoul(buffer,NULL,16);
+  		implementer = (midr_el1 >> 24) & 0xFF;
+  		p        = (midr_el1 >> 4)  & 0xFFF;
+		fclose(infile);
+		sprintf(buffer,"/sys/devices/system/cpu/cpu%d/cpu_capability",i);
+		infile = fopen(buffer,"r");
+		if (infile) {
+			(void)fgets(buffer, sizeof(buffer), infile);
+			cpucap=strtoul(buffer,NULL,16);
+			fclose(infile);
+			if (cpucap >= 1000) cpuhiperf++;
+			else if (cpucap >=500) cpumidperf++;
+			else cpulowperf++;
+			if (cpucap >=1000) part = p;
+		} else if (implementer == 0x41 ){
+			if (p >= 0xd4b) cpuhiperf++:
+			else if (p>= 0xd07) cpumidperf++;
+			else cpulowperf++;
+		} else cpulowperf++;
+	}
+	if (!part) part = p;
+#else	
     snprintf(coremsg, 128, "Kernel lacks cpuid feature support. Auto detection of core type failed !!!\n");
     openblas_warning(1, coremsg);
     return NULL;