Add checking of correct likely/unlikely

To use:
- Compile with -DUSE_MY_LIKELY
- Change (with replace) all likely/unlikely to my_likely/my_/unlikely
  replace likely my_likely unlikely my_unlikely -- *c *h
- Start mysqld with -T
- run some test
- When mysqld has shut down cleanely, report will be on stderr

include/my_global.h

@@ -189,15 +189,6 @@
 #define __builtin_expect(x, expected_value) (x)
 #endif
 
-/**
-  The semantics of builtin_expect() are that
-  1) its two arguments are long
-  2) it's likely that they are ==
-  Those of our likely(x) are that x can be bool/int/longlong/pointer.
-*/
-#define likely(x)	__builtin_expect(((x) != 0),1)
-#define unlikely(x)	__builtin_expect(((x) != 0),0)
-
 /* Fix problem with S_ISLNK() on Linux */
 #if defined(TARGET_OS_LINUX) || defined(__GLIBC__)
 #undef  _GNU_SOURCE
@@ -384,6 +375,36 @@ C_MODE_END
 #include <crypt.h>
 #endif
 
+/* Add checking if we are using likely/unlikely wrong */
+#ifdef CHECK_UNLIKELY
+C_MODE_START
+extern void init_my_likely(), end_my_likely(FILE *);
+extern int my_likely_ok(const char *file_name, uint line);
+extern int my_likely_fail(const char *file_name, uint line);
+C_MODE_END
+
+#define likely(A) ((A) ? (my_likely_ok(__FILE__, __LINE__),1) : (my_likely_fail(__FILE__, __LINE__), 0))
+#define unlikely(A) ((A) ? (my_likely_fail(__FILE__, __LINE__),1) : (my_likely_ok(__FILE__, __LINE__), 0))
+/*
+  These macros should be used when the check fails often when running benchmarks but
+  we know for sure that the check is correct in a production environment
+*/
+#define checked_likely(A) (A)
+#define checked_unlikely(A) (A)
+#else
+/**
+  The semantics of builtin_expect() are that
+  1) its two arguments are long
+  2) it's likely that they are ==
+  Those of our likely(x) are that x can be bool/int/longlong/pointer.
+*/
+
+#define likely(x)	__builtin_expect(((x) != 0),1)
+#define unlikely(x)	__builtin_expect(((x) != 0),0)
+#define checked_likely(x) likely(x)
+#define checked_unlikely(x) unlikely(x)
+#endif /* CHECK_UNLIKELY */
+
 /*
   A lot of our programs uses asserts, so better to always include it
   This also fixes a problem when people uses DBUG_ASSERT without including
@@ -1279,5 +1300,4 @@ static inline double rint(double x)
 #else
 #define NOT_FIXED_DEC           FLOATING_POINT_DECIMALS
 #endif
-
 #endif /* my_global_h */

mysys/CMakeLists.txt

@@ -43,7 +43,7 @@ SET(MYSYS_SOURCES  array.c charset-def.c charset.c checksum.c my_default.c
 				my_getncpus.c my_safehash.c my_chmod.c my_rnd.c
                                 my_uuid.c wqueue.c waiting_threads.c ma_dyncol.c ../sql-common/my_time.c
 				my_rdtsc.c my_context.c psi_noop.c
-				my_atomic_writes.c
+				my_atomic_writes.c my_likely.c
                                 file_logger.c my_dlerror.c)
 
 IF (WIN32)

mysys/my_init.c

@@ -121,6 +121,9 @@ my_bool my_init(void)
     DBUG_PRINT("exit", ("home: '%s'", home_dir));
 #ifdef __WIN__
     win32_init_tcp_ip();
+#endif
+#ifdef CHECK_UNLIKELY
+    init_my_likely();
 #endif
     DBUG_RETURN(0);
   }
@@ -166,6 +169,9 @@ void my_end(int infoflag)
       DBUG_PRINT("error", ("%s", ebuff));
       my_print_open_files();
     }
+#ifdef CHECK_UNLIKELY
+    end_my_likely(info_file);
+#endif
   }
   free_charsets();
   my_error_unregister_all();

mysys/my_likely.c

+/* Copyright (c) 2018, MariaDB Corporation Ab.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
+
+/*
+  Checks that my_likely/my_unlikely is correctly used
+
+  Note that we can't use mysql_mutex or my_malloc here as these
+  uses likely() macros and the likely_mutex would be used twice
+*/
+
+#include "mysys_priv.h"
+#include <hash.h>
+#include <m_ctype.h>
+
+#ifndef CHECK_UNLIKEY
+my_bool likely_inited= 0;
+
+typedef struct st_likely_entry
+{
+  const char *key;
+  size_t key_length;
+  uint line;
+  ulonglong ok,fail;
+} LIKELY_ENTRY;
+
+static uchar *get_likely_key(LIKELY_ENTRY *part, size_t *length,
+                             my_bool not_used __attribute__((unused)))
+{
+  *length= part->key_length;
+  return (uchar*) part->key;
+}
+
+pthread_mutex_t likely_mutex;
+HASH likely_hash;
+
+void init_my_likely()
+{
+  /* Allocate big enough to avoid malloc calls */
+  my_hash_init2(&likely_hash, 10000, &my_charset_bin,
+                1024, 0, 0,
+                (my_hash_get_key) get_likely_key, 0,
+                free, HASH_UNIQUE);
+  likely_inited= 1;
+  pthread_mutex_init(&likely_mutex, MY_MUTEX_INIT_FAST);
+}
+
+static int likely_cmp(LIKELY_ENTRY **a, LIKELY_ENTRY **b)
+{
+  int cmp;
+  if ((cmp= strcmp((*a)->key, (*b)->key)))
+    return cmp;
+  return (int) ((*a)->line - (*b)->line);
+}
+
+
+void end_my_likely(FILE *out)
+{
+  uint i;
+  FILE *likely_file;
+  my_bool do_close= 0;
+  LIKELY_ENTRY **sort_ptr= 0;
+
+  likely_inited= 0;
+
+  if (!(likely_file= out))
+  {
+    char name[80];
+    sprintf(name, "/tmp/unlikely-%lu.out", (ulong) getpid());
+    if ((likely_file= my_fopen(name, O_TRUNC | O_WRONLY, MYF(MY_WME))))
+      do_close= 1;
+    else
+      likely_file= stderr;
+  }
+  fflush(likely_file);
+  fputs("Wrong likely/unlikely usage:\n", likely_file);
+  if (!(sort_ptr= (LIKELY_ENTRY**)
+        malloc(sizeof(LIKELY_ENTRY*) *likely_hash.records)))
+  {
+    fprintf(stderr, "ERROR: Out of memory in end_my_likely\n");
+    goto err;
+  }
+
+  for (i=0 ; i < likely_hash.records ; i++)
+    sort_ptr[i]= (LIKELY_ENTRY *) my_hash_element(&likely_hash, i);
+
+  my_qsort(sort_ptr, likely_hash.records, sizeof(LIKELY_ENTRY*),
+           (qsort_cmp) likely_cmp);
+  
+  for (i=0 ; i < likely_hash.records ; i++)
+  {
+    LIKELY_ENTRY *entry= sort_ptr[i];
+    if (entry->fail > entry->ok)
+      fprintf(likely_file,
+              "%50s  line: %6u  ok: %8lld  fail: %8lld\n",
+              entry->key, entry->line, entry->ok, entry->fail);
+  }
+  fputs("\n", likely_file);
+  fflush(likely_file);
+err:
+  free((void*) sort_ptr);
+  if (do_close)
+    my_fclose(likely_file, MYF(MY_WME));
+  pthread_mutex_destroy(&likely_mutex);
+  my_hash_free(&likely_hash);
+}
+
+
+static LIKELY_ENTRY *my_likely_find(const char *file_name, uint line)
+{
+  char key[80], *pos;
+  LIKELY_ENTRY *entry;
+  uint length;
+
+  if (!likely_inited)
+    return 0;
+
+  pos= strnmov(key, file_name, sizeof(key)-4);
+  int3store(pos+1, line);
+  length= (pos-key)+4;
+
+  pthread_mutex_lock(&likely_mutex);
+  if (!(entry= (LIKELY_ENTRY*) my_hash_search(&likely_hash, (uchar*) key,
+                                              length)))
+  {
+    if (!(entry= (LIKELY_ENTRY *) malloc(sizeof(*entry) + length)))
+      return 0;
+    entry->key= (char*) (entry+1);
+    memcpy((void*) entry->key, key, length);
+    entry->key_length= length;
+    entry->line= line;
+    entry->ok= entry->fail= 0;
+
+    if (my_hash_insert(&likely_hash, (void*) entry))
+    {
+      pthread_mutex_unlock(&likely_mutex);
+      free(entry);
+      return 0;
+    }
+  }
+  pthread_mutex_unlock(&likely_mutex);
+  return entry;
+}
+
+
+int my_likely_ok(const char *file_name, uint line)
+{
+  LIKELY_ENTRY *entry= my_likely_find(file_name, line);
+  if (entry)
+    entry->ok++;
+  return 0;
+}
+
+
+int my_likely_fail(const char *file_name, uint line)
+{
+  LIKELY_ENTRY *entry= my_likely_find(file_name, line);
+  if (entry)
+    entry->fail++;
+  return 0;
+}
+#endif /* CHECK_UNLIKEY */

sql/gen_lex_hash.cc

@@ -78,6 +78,7 @@ So, we can read full search-structure as 32-bit word
 */
 
 #define NO_YACC_SYMBOLS
+#undef CHECK_UNLIKELY
 #include "mariadb.h"
 #include "mysql_version.h"
 #include "lex.h"

sql/table_cache.cc

@@ -838,7 +838,7 @@ TABLE_SHARE *tdc_acquire_share(THD *thd, TABLE_LIST *tl, uint flags,
     /* note that tdc_acquire_share() *always* uses discovery */
     open_table_def(thd, share, flags | GTS_USE_DISCOVERY);
 
-    if (unlikely(share->error))
+    if (checked_unlikely(share->error))
     {
       free_table_share(share);
       lf_hash_delete(&tdc_hash, thd->tdc_hash_pins, key, key_length);