qht: require a default comparison function

qht_lookup now uses the default cmp function. qht_lookup_custom is defined
to retain the old behaviour, that is a cmp function is explicitly provided.

qht_insert will gain use of the default cmp in the next patch.

Note that we move qht_lookup_custom's @func to be the last argument,
which makes the new qht_lookup as simple as possible.
Instead of this (i.e. keeping @func 2nd):
0000000000010750 <qht_lookup>:
   10750:       89 d1                   mov    %edx,%ecx
   10752:       48 89 f2                mov    %rsi,%rdx
   10755:       48 8b 77 08             mov    0x8(%rdi),%rsi
   10759:       e9 22 ff ff ff          jmpq   10680 <qht_lookup_custom>
   1075e:       66 90                   xchg   %ax,%ax

We get:
0000000000010740 <qht_lookup>:
   10740:       48 8b 4f 08             mov    0x8(%rdi),%rcx
   10744:       e9 37 ff ff ff          jmpq   10680 <qht_lookup_custom>
   10749:       0f 1f 80 00 00 00 00    nopl   0x0(%rax)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

2 files changed, 17 insertions, 12 deletions

diff --git a/tests/qht-bench.c b/tests/qht-bench.c
index 4cabdfd62a..c94ac25158 100644
--- a/tests/qht-bench.c
+++ b/tests/qht-bench.c
@@ -93,10 +93,10 @@ static void usage_complete(int argc, char *argv[])
     exit(-1);
 }
 
-static bool is_equal(const void *obj, const void *userp)
+static bool is_equal(const void *ap, const void *bp)
 {
-    const long *a = obj;
-    const long *b = userp;
+    const long *a = ap;
+    const long *b = bp;
 
     return *a == *b;
 }
@@ -150,7 +150,7 @@ static void do_rw(struct thread_info *info)
 
         p = &keys[info->r & (lookup_range - 1)];
         hash = h(*p);
-        read = qht_lookup(&ht, is_equal, p, hash);
+        read = qht_lookup(&ht, p, hash);
         if (read) {
             stats->rd++;
         } else {
@@ -162,7 +162,7 @@ static void do_rw(struct thread_info *info)
         if (info->write_op) {
             bool written = false;
 
-            if (qht_lookup(&ht, is_equal, p, hash) == NULL) {
+            if (qht_lookup(&ht, p, hash) == NULL) {
                 written = qht_insert(&ht, p, hash);
             }
             if (written) {
@@ -173,7 +173,7 @@ static void do_rw(struct thread_info *info)
         } else {
             bool removed = false;
 
-            if (qht_lookup(&ht, is_equal, p, hash)) {
+            if (qht_lookup(&ht, p, hash)) {
                 removed = qht_remove(&ht, p, hash);
             }
             if (removed) {
@@ -308,7 +308,7 @@ static void htable_init(void)
     }
 
     /* initialize the hash table */
-    qht_init(&ht, qht_n_elems, qht_mode);
+    qht_init(&ht, is_equal, qht_n_elems, qht_mode);
     assert(init_size <= init_range);
 
     pr_params();
diff --git a/tests/test-qht.c b/tests/test-qht.c
index 9b7423abb6..b069881342 100644
--- a/tests/test-qht.c
+++ b/tests/test-qht.c
@@ -13,10 +13,10 @@
 static struct qht ht;
 static int32_t arr[N * 2];
 
-static bool is_equal(const void *obj, const void *userp)
+static bool is_equal(const void *ap, const void *bp)
 {
-    const int32_t *a = obj;
-    const int32_t *b = userp;
+    const int32_t *a = ap;
+    const int32_t *b = bp;
 
     return *a == *b;
 }
@@ -60,7 +60,12 @@ static void check(int a, int b, bool expected)
 
         val = i;
         hash = i;
-        p = qht_lookup(&ht, is_equal, &val, hash);
+        /* test both lookup variants; results should be the same */
+        if (i % 2) {
+            p = qht_lookup(&ht, &val, hash);
+        } else {
+            p = qht_lookup_custom(&ht, &val, hash, is_equal);
+        }
         g_assert_true(!!p == expected);
     }
     rcu_read_unlock();
@@ -102,7 +107,7 @@ static void qht_do_test(unsigned int mode, size_t init_entries)
     /* under KVM we might fetch stats from an uninitialized qht */
     check_n(0);
 
-    qht_init(&ht, 0, mode);
+    qht_init(&ht, is_equal, 0, mode);
 
     check_n(0);
     insert(0, N);