[core] Add branch prediction annotations to Parrot.

From: Mark Glines <mark@glines.org>


---

 include/parrot/compiler.h   |    8 ++++++++
 include/parrot/exceptions.h |    4 ++--
 src/gc/mark_sweep.c         |    2 +-
 src/hash.c                  |    6 +++---
 4 files changed, 14 insertions(+), 6 deletions(-)


diff --git a/include/parrot/compiler.h b/include/parrot/compiler.h
index 7657801..051718d 100644
--- a/include/parrot/compiler.h
+++ b/include/parrot/compiler.h
@@ -28,6 +28,14 @@
 #  define PARROT_HAS_SAL 0
 #endif
 
+#ifdef __GNUC__
+# define likely(x)      __builtin_expect(!!(x), 1)
+# define unlikely(x)    __builtin_expect(!!(x), 0)
+#else
+# define likely(x)      (x)
+# define unlikely(x)    (x)
+#endif
+
 #ifdef HASATTRIBUTE_NEVER_WORKS
  #  error This attribute can never succeed.  Something has mis-sniffed your configuration.
 #endif
diff --git a/include/parrot/exceptions.h b/include/parrot/exceptions.h
index 1c0a3a2..14def86 100644
--- a/include/parrot/exceptions.h
+++ b/include/parrot/exceptions.h
@@ -280,8 +280,8 @@ void Parrot_print_backtrace(void);
 #  define PARROT_ASSERT_ARG(x) (0)
 #  define ASSERT_ARGS(a)
 #else
-#  define PARROT_ASSERT(x) (x) ? ((void)0) : Parrot_confess(#x, __FILE__, __LINE__)
-#  define PARROT_ASSERT_ARG(x) ((x) ? (0) : (Parrot_confess(#x, __FILE__, __LINE__), 0))
+#  define PARROT_ASSERT(x) likely(x) ? ((void)0) : Parrot_confess(#x, __FILE__, __LINE__)
+#  define PARROT_ASSERT_ARG(x) (likely(x) ? (0) : (Parrot_confess(#x, __FILE__, __LINE__), 0))
 
 #  ifdef __GNUC__
 #    define ASSERT_ARGS(a) ASSERT_ARGS_ ## a ;
diff --git a/src/gc/mark_sweep.c b/src/gc/mark_sweep.c
index 8c2b680..d482b6a 100644
--- a/src/gc/mark_sweep.c
+++ b/src/gc/mark_sweep.c
@@ -771,7 +771,7 @@ free_pmc_in_pool(PARROT_INTERP, SHIM(Small_Object_Pool *pool),
     Arenas * const arena_base = interp->arena_base;
 
     /* TODO collect objects with finalizers */
-    if (PObj_needs_early_gc_TEST(p))
+    if (unlikely(PObj_needs_early_gc_TEST(p)))
         --arena_base->num_early_gc_PMCs;
 
     if (PObj_active_destroy_TEST(p))
diff --git a/src/hash.c b/src/hash.c
index 6d5dc0d..0bd7054 100644
--- a/src/hash.c
+++ b/src/hash.c
@@ -1192,7 +1192,7 @@ parrot_hash_get_bucket(PARROT_INTERP, ARGIN(const Hash *hash), ARGIN(const void
 {
     ASSERT_ARGS(parrot_hash_get_bucket)
 
-    if (hash->entries <= 0)
+    if (unlikely(hash->entries <= 0))
         return NULL;
 
     /* a very fast search for very small hashes */
@@ -1214,9 +1214,9 @@ parrot_hash_get_bucket(PARROT_INTERP, ARGIN(const Hash *hash), ARGIN(const void
         const UINTVAL hashval = (hash->hash_val)(interp, key, hash->seed);
         HashBucket   *bucket  = hash->bi[hashval & hash->mask];
 
-        while (bucket) {
+        while (likely(bucket)) {
             /* key equality is always a match, so it's worth checking */
-            if (bucket->key == key
+            if (unlikely(bucket->key == key)
 
             /* ... but the slower comparison is more accurate */
             || ((hash->compare)(interp, key, bucket->key) == 0))