Add prefetch to PerfUtils

Author: hq6

src/Util.h

@@ -32,6 +32,9 @@
 #include <unordered_set>
 #include <vector>
 
+#include <mmintrin.h>
+#include <xmmintrin.h>
+
 namespace PerfUtils {
 
 /**
@@ -195,6 +198,40 @@ serialReadPmc(int ecx) {
     return retVal;
 }
 
+/**
+ * Prefetch the cache lines containing [object, object + numBytes) into the
+ * processor's caches.
+ * The best docs for this are in the Intel instruction set reference under
+ * PREFETCH.
+ * \param object
+ *      The start of the region of memory to prefetch.
+ * \param numBytes
+ *      The size of the region of memory to prefetch.
+ */
+static inline void
+prefetch(const void* object, uint64_t numBytes)
+{
+    uint64_t offset = reinterpret_cast<uint64_t>(object) & 0x3fUL;
+    const char* p = reinterpret_cast<const char*>(object) - offset;
+    for (uint64_t i = 0; i < offset + numBytes; i += 64)
+        _mm_prefetch(p + i, _MM_HINT_T0);
+}
+
+/**
+ * Prefetch the cache lines containing the given object into the
+ * processor's caches.
+ * The best docs for this are in the Intel instruction set reference under
+ * PREFETCHh.
+ * \param object
+ *      A pointer to the object in memory to prefetch.
+ */
+template<typename T>
+static inline void
+prefetch(const T* object)
+{
+    prefetch(object, sizeof(*object));
+}
+
 #define PERFUTILS_DIE(format_, ...)                     \
     do {                                                \
         fprintf(stderr, format_, ##__VA_ARGS__);        \