Added basic profiling support

src/include/gpxe/profile.h

@@ -0,0 +1,78 @@
+#ifndef _GPXE_PROFILE_H
+#define _GPXE_PROFILE_H
+
+/** @file
+ *
+ * Profiling
+ *
+ */
+
+#include <stdint.h>
+
+/**
+ * A data structure for storing profiling information
+ */
+union profiler {
+	/** Timestamp (in CPU-specific "ticks") */
+	uint64_t timestamp;
+	/** Registers returned by rdtsc.
+	 *
+	 * This part should really be architecture-specific code.
+	 */
+	struct {
+		uint32_t eax;
+		uint32_t edx;
+	} rdtsc;
+};
+
+/**
+ * Static per-object profiler, for use with simple_profile()
+ */
+static union profiler simple_profiler;
+
+/**
+ * Perform profiling
+ *
+ * @v profiler		Profiler data structure
+ * @ret delta		Elapsed ticks since last call to profile().
+ *
+ * Call profile() both before and after the code you wish to measure.
+ * The "after" call will return the measurement.  For example:
+ *
+ * @code
+ *
+ *     profile ( &profiler );
+ *     ... do something here ...
+ *     printf ( "It took %ld ticks to execute\n", profile ( &profiler ) );
+ *
+ * @endcode
+ */
+static inline __attribute__ (( always_inline )) unsigned long
+profile ( union profiler *profiler ) {
+	uint64_t last_timestamp = profiler->timestamp;
+
+	__asm__ __volatile__ ( "rdtsc" :
+			       "=a" ( profiler->rdtsc.eax ),
+			       "=d" ( profiler->rdtsc.edx ) );
+	return ( profiler->timestamp - last_timestamp );
+}
+
+/**
+ * Perform profiling
+ *
+ * @ret delta		Elapsed ticks since last call to profile().
+ *
+ * When you only need one profiler, you can avoid the hassle of
+ * creating your own @c profiler data structure by using
+ * simple_profile() instead.
+ *
+ * simple_profile() is equivalent to profile(&simple_profiler), where
+ * @c simple_profiler is a @c profiler data structure that is static
+ * to each object which includes @c profile.h.
+ */
+static inline __attribute__ (( always_inline )) unsigned long
+simple_profile ( void ) {
+	return profile ( &simple_profiler );
+}
+
+#endif /* _GPXE_PROFILE_H */