Add dmnsn_[un]likely() macros and a profiling framework.

1 files changed, 106 insertions, 0 deletions

diff --git a/libdimension/profile.c b/libdimension/profile.c
new file mode 100644
index 0000000..c88e3ef
--- /dev/null
+++ b/libdimension/profile.c
@@ -0,0 +1,106 @@
+/*************************************************************************
+ * Copyright (C) 2010 Tavian Barnes <tavianator@gmail.com>               *
+ *                                                                       *
+ * This file is part of The Dimension Library.                           *
+ *                                                                       *
+ * The Dimension Library is free software; you can redistribute it and/  *
+ * or modify it under the terms of the GNU Lesser General Public License *
+ * as published by the Free Software Foundation; either version 3 of the *
+ * License, or (at your option) any later version.                       *
+ *                                                                       *
+ * The Dimension Library is distributed in the hope that it will be      *
+ * useful, but WITHOUT ANY WARRANTY; without even the implied warranty   *
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU  *
+ * Lesser General Public License for more details.                       *
+ *                                                                       *
+ * You should have received a copy of the GNU Lesser General Public      *
+ * License along with this program.  If not, see                         *
+ * <http://www.gnu.org/licenses/>.                                       *
+ *************************************************************************/
+
+/**
+ * @file
+ * Branch profile accounting.
+ */
+
+#include "dimension-impl.h"
+#include <pthread.h>
+#include <stdio.h>
+#include <inttypes.h>
+
+/** Info for one predicted branch. */
+typedef struct {
+  char *location;
+  uint64_t predicted, branches;
+} dmnsn_profile_info;
+
+/** Count of mispredicted branches. */
+static dmnsn_dictionary *dmnsn_profile_data = NULL;
+/** Mutex which protects \c dmnsn_profile_data. */
+static pthread_mutex_t dmnsn_profile_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+bool
+dmnsn_expect(bool result, bool expected, const char *func, const char *file,
+             unsigned int line)
+{
+  int size = snprintf(NULL, 0, "%s:%s:%u", file, func, line) + 1;
+  if (size < 1) {
+    dmnsn_error(DMNSN_SEVERITY_MEDIUM, "sprintf() failed.");
+  } else {
+    char key[size];
+    if (snprintf(key, size, "%s:%s:%u", file, func, line) > 0) {
+      if (pthread_mutex_lock(&dmnsn_profile_mutex) != 0) {
+        dmnsn_error(DMNSN_SEVERITY_MEDIUM, "Couldn't lock mutex.");
+      }
+
+      if (!dmnsn_profile_data) {
+        dmnsn_profile_data = dmnsn_new_dictionary(sizeof(dmnsn_profile_info));
+      }
+      dmnsn_profile_info *info = dmnsn_dictionary_at(dmnsn_profile_data, key);
+      if (info) {
+        ++info->branches;
+        if (result == expected) {
+          ++info->predicted;
+        }
+      } else {
+        dmnsn_profile_info info = {
+          .location  = dmnsn_strdup(key),
+          .predicted = (result == expected) ? 1 : 0,
+          .branches  = 1
+        };
+        dmnsn_dictionary_insert(dmnsn_profile_data, key, &info);
+      }
+
+      if (pthread_mutex_unlock(&dmnsn_profile_mutex) != 0) {
+        dmnsn_error(DMNSN_SEVERITY_MEDIUM, "Couldn't lock mutex.");
+      }
+    } else {
+      dmnsn_error(DMNSN_SEVERITY_MEDIUM, "sprintf() failed.");
+    }
+  }
+
+  return result;
+}
+
+static void
+dmnsn_print_bad_prediction(void *ptr)
+{
+  dmnsn_profile_info *info = ptr;
+  double rate = ((double)info->predicted)/info->branches;
+  if (rate < 0.75 || info->branches < 100000) {
+    fprintf(stderr,
+            "Bad branch prediction: %s: %" PRIu64 "/%" PRIu64 "\n",
+            info->location, info->predicted, info->branches);
+  }
+
+  dmnsn_free(info->location);
+}
+
+static void __attribute__((destructor))
+dmnsn_print_bad_predictions(void)
+{
+  if (dmnsn_profile_data) {
+    dmnsn_dictionary_apply(dmnsn_profile_data, &dmnsn_print_bad_prediction);
+    dmnsn_delete_dictionary(dmnsn_profile_data);
+  }
+}