Detect Intel CPUs with hybrid cores and warn about missing support

Ping pytorch#334, pytorch#247

Author: dlenski

src/x86/init.c

@@ -75,4 +75,18 @@ void cpuinfo_x86_init_processor(struct cpuinfo_x86_processor* processor) {
 		memcpy(processor->brand_string, brand_string, sizeof(processor->brand_string));
 		cpuinfo_log_debug("raw CPUID brand string: \"%48s\"", processor->brand_string);
 	}
+
+	/**
+	* Warn that hybrid cores are not yet properly supported.
+	* https://www.intel.com/content/www/us/en/developer/articles/guide/12th-gen-intel-core-processor-gamedev-guide.html#inpage-nav-1-5-2
+	* "CPUID, by design, returns different values depending on the core it is executed on.
+	* On hybrid cores more of the CPUID leaves will have data that varies"
+	*/
+	if (max_base_index >= UINT32_C(0x7)) {
+		const struct cpuid_regs leaf7 = cpuidex(UINT32_C(0x7), 0);
+		const bool is_hybrid = !!(leaf7.edx & UINT32_C(0x00004000));
+
+		if (is_hybrid)
+			cpuinfo_log_warning("This is a hybrid processor (CPUID leaf7.edx bit 15 is set). We do not yet properly support enumeration of x86 hybrid cores.");
+	}
 }