Add branch prediction information and start using it. (#226)

Signed-off-by: Samuel K. Gutierrez <[email protected]>

src/qvi-bbuff.cc

@@ -31,15 +31,15 @@ struct qvi_bbuff_s {
     {
         capacity = min_growth;
         data = calloc(capacity, sizeof(byte_t));
-        if (!data) throw qvi_runtime_error();
+        if (qvi_unlikely(!data)) throw qvi_runtime_error();
     }
     /** Copy constructor. */
     qvi_bbuff_s(
         const qvi_bbuff_s &src
     ) : qvi_bbuff_s()
     {
         const int rc = qvi_bbuff_append(this, src.data, src.size);
-        if (rc != QV_SUCCESS) throw qvi_runtime_error();
+        if (qvi_unlikely(rc != QV_SUCCESS)) throw qvi_runtime_error();
     }
     /** Destructor. */
     ~qvi_bbuff_s(void)
@@ -95,7 +95,7 @@ qvi_bbuff_append(
         // New capacity.
         const size_t new_capacity = req_capacity + buff->min_growth;
         void *new_data = calloc(new_capacity, sizeof(byte_t));
-        if (!new_data) return QV_ERR_OOR;
+        if (qvi_unlikely(!new_data)) return QV_ERR_OOR;
         // Memory allocation successful.
         memmove(new_data, buff->data, buff->size);
         free(buff->data);

src/qvi-macros.h

@@ -17,6 +17,16 @@
 #ifndef QVI_MACROS_H
 #define QVI_MACROS_H
 
+/**
+ * Add branch prediction information: will likely happen.
+ */
+#define qvi_likely(x) __builtin_expect(!!(x), 1)
+
+/**
+ * Add branch prediction information: won't likely happen.
+ */
+#define qvi_unlikely(x) __builtin_expect(!!(x), 0)
+
 /**
  * Convenience macro used to silence warnings about unused variables.
  *

src/qvi-task.cc

@@ -37,7 +37,7 @@ struct qvi_task_s {
     {
         std::string url;
         const int rc = qvi_url(url);
-        if (rc != QV_SUCCESS) {
+        if (qvi_unlikely(rc != QV_SUCCESS)) {
             qvi_log_error("{}", qvi_conn_ers());
             return rc;
         }
@@ -52,7 +52,7 @@ struct qvi_task_s {
         const int rc = qvi_rmi_task_get_cpubind(
             rmi, me(), &current_bind
         );
-        if (rc != QV_SUCCESS) return rc;
+        if (qvi_unlikely(rc != QV_SUCCESS)) return rc;
 
         stack.push(qvi_hwloc_bitmap_s(current_bind));
         hwloc_bitmap_free(current_bind);
@@ -62,13 +62,13 @@ struct qvi_task_s {
     qvi_task_s(void)
     {
         int rc = qvi_rmi_client_new(&rmi);
-        if (rc != QV_SUCCESS) throw qvi_runtime_error();
+        if (qvi_unlikely(rc != QV_SUCCESS)) throw qvi_runtime_error();
         // Connect to our server.
         rc = connect_to_server();
-        if (rc != QV_SUCCESS) throw qvi_runtime_error();
+        if (qvi_unlikely(rc != QV_SUCCESS)) throw qvi_runtime_error();
         // Initialize our bind stack.
         rc = bind_stack_init();
-        if (rc != QV_SUCCESS) throw qvi_runtime_error();
+        if (qvi_unlikely(rc != QV_SUCCESS)) throw qvi_runtime_error();
     }
     /** Copy constructor. */
     qvi_task_s(const qvi_task_s &src) = delete;
@@ -91,7 +91,7 @@ struct qvi_task_s {
         const int rc = qvi_rmi_task_set_cpubind_from_cpuset(
             rmi, me(), bitmap_copy.cdata()
         );
-        if (rc != QV_SUCCESS) return rc;
+        if (qvi_unlikely(rc != QV_SUCCESS)) return rc;
         // Push bitmap onto stack.
         stack.push(bitmap_copy);
         return rc;