diff --git a/configure b/configure
index 6df241a..185ecba 100755
--- a/configure
+++ b/configure
@@ -170,13 +170,15 @@ for option; do
 		echo "  --mandir=N               Manual pages directory (default is ${PREFIX}/man)"
 		echo "  --prefix=N               Installs library files in N (default is $PREFIX)"
 		echo
-		echo "The following options will modify code generation."
-		echo "  --cores=N                Specify number of cores available on target machine"
+		echo "The following options will affect generated code."
 		echo "  --enable-pointer-packing Assumes address encoding is subset of pointer range"
-		echo "  --enable-rtm             Enable restricted transactional memory (x86_64 only)"
+		echo "  --enable-rtm             Enable restricted transactional memory (power, x86_64)"
 		echo "  --memory-model=N         Specify memory model (currently tso, pso or rmo)"
 		echo "  --vma-bits=N             Specify valid number of VMA bits"
 		echo
+		echo "The following options affect regression testing."
+		echo "  --cores=N                Specify number of cores available on target machine"
+		echo
 		echo "The following environment variables may be used:"
 		echo "   CC       C compiler command"
 		echo "   CFLAGS   C compiler flags"
diff --git a/doc/Makefile.in b/doc/Makefile.in
index 85643e9..1915f2a 100644
--- a/doc/Makefile.in
+++ b/doc/Makefile.in
@@ -99,6 +99,7 @@ OBJECTS=CK_ARRAY_FOREACH		\
 	ck_rhs_next			\
 	ck_rhs_get			\
 	ck_rhs_put			\
+	ck_rhs_put_unique		\
 	ck_rhs_set			\
 	ck_rhs_fas			\
 	ck_rhs_remove			\
@@ -190,6 +191,18 @@ html:
 		   $(BUILD_DIR)/doc/$$target$(HTML_SUFFIX); 		\
 	done
 
+# check for entries that are missing in OBJECTS
+objcheck: all
+	for file in `ls * | egrep '(ck|CK)_' | egrep -v "($(GZIP_SUFFIX)|$(HTML_SUFFIX))$$"`; do \
+		if [ ! -f $${file}$(GZIP_SUFFIX) ]; then	\
+			echo "$$file is missing from OBJECTS" >&2;	\
+		fi;						\
+	done
+
+# check for stale references
+refcheck:
+	@./refcheck.pl $(OBJECTS)
+
 install:
 	mkdir -p $(DESTDIR)/$(MANDIR)/man3 || exit
 	cp *$(GZIP_SUFFIX) $(DESTDIR)/$(MANDIR)/man3 || exit
@@ -200,5 +213,5 @@ uninstall:
 	done
 
 clean:
-	rm -f $(BUILD_DIR)/doc/*~ $(BUILD_DIR)/doc/*.3.gz $(BUILD_DIR)/doc/*.html
+	rm -f $(BUILD_DIR)/doc/*~ $(BUILD_DIR)/doc/*$(GZIP_SUFFIX) $(BUILD_DIR)/doc/*$(HTML_SUFFIX)
 
diff --git a/doc/ck_ht_init b/doc/ck_ht_init
index 602483d..757a39a 100644
--- a/doc/ck_ht_init
+++ b/doc/ck_ht_init
@@ -76,7 +76,7 @@ with using the
 .Xr ck_ht_entry_key_direct 3 ,
 .Xr ck_ht_entry_value_direct 3
 and
-.Xr ck_entry_set_direct 3
+.Xr ck_ht_entry_set_direct 3
 functions. Attempting a hash table operation with a key of value of 0 or
 UINTPTR_MAX will result in undefined behavior.
 .El
diff --git a/doc/refcheck.pl b/doc/refcheck.pl
new file mode 100755
index 0000000..1ed3a65
--- /dev/null
+++ b/doc/refcheck.pl
@@ -0,0 +1,27 @@
+#!/usr/bin/perl
+
+use warnings;
+use strict;
+
+my @files = @ARGV;
+
+my $h;
+
+foreach my $file (@files) {
+    $h->{$file} = 1;
+}
+
+foreach my $file (@files) {
+    open(my $fh, "<", $file) or die "cannot open < $file: $!";
+    while (<$fh>) {
+        chomp;
+        if ($_ =~ /\.Xr ((ck|CK)_[a-zA-Z_]+) ([0-9])/) {
+	    my $name = $1;
+	    my $section = $3;
+	    if (!$h->{$name}) {
+		print STDERR "$file: ref to missing ${name}($section)\n";
+	    }
+        }
+    }
+    close($fh) or die("cannot close $file: $!");
+}
diff --git a/include/ck_ht.h b/include/ck_ht.h
index f58a925..df032ee 100644
--- a/include/ck_ht.h
+++ b/include/ck_ht.h
@@ -27,6 +27,10 @@
 #ifndef _CK_HT_H
 #define _CK_HT_H
 
+#ifndef _CK_HT_IM
+#warning ck_ht is deprecated, see ck_hm, ck_hs or ck_rhs.
+#endif /* !_CK_HT_IM */
+
 #include <ck_pr.h>
 
 #if defined(CK_F_PR_LOAD_64) && defined(CK_F_PR_STORE_64)
diff --git a/include/ck_pr.h b/include/ck_pr.h
index 3ceea4c..f5533bb 100644
--- a/include/ck_pr.h
+++ b/include/ck_pr.h
@@ -138,6 +138,17 @@ CK_PR_FENCE_NOOP(release)
 #undef CK_PR_FENCE_EMIT
 #undef CK_PR_FENCE_NOOP
 
+#ifndef CK_F_PR_RFO
+#define CK_F_PR_RFO
+CK_CC_INLINE static void
+ck_pr_rfo(const void *m)
+{
+
+	(void)m;
+	return;
+}
+#endif /* CK_F_PR_RFO */
+
 #define CK_PR_BIN(K, S, M, T, P, C)					\
 	CK_CC_INLINE static void					\
 	ck_pr_##K##_##S(M *target, T value)				\
diff --git a/include/gcc/x86_64/ck_pr.h b/include/gcc/x86_64/ck_pr.h
index 5dfa626..1a71d31 100644
--- a/include/gcc/x86_64/ck_pr.h
+++ b/include/gcc/x86_64/ck_pr.h
@@ -91,6 +91,26 @@ CK_PR_FENCE(acquire, "mfence")
 
 #undef CK_PR_FENCE
 
+/*
+ * Read for ownership. Older compilers will generate the 32-bit
+ * 3DNow! variant which is binary compatible with x86-64 variant
+ * of prefetchw.
+ */
+#ifndef CK_F_PR_RFO
+#define CK_F_PR_RFO
+CK_CC_INLINE static void
+ck_pr_rfo(const void *m)
+{
+
+	__asm__ __volatile__("prefetchw (%0)"
+	    :
+	    : "r" (m)
+	    : "memory");
+
+	return;
+}
+#endif /* CK_F_PR_RFO */
+
 /*
  * Atomic fetch-and-store operations.
  */
diff --git a/include/spinlock/anderson.h b/include/spinlock/anderson.h
index 8b2cf87..1386b18 100644
--- a/include/spinlock/anderson.h
+++ b/include/spinlock/anderson.h
@@ -162,4 +162,3 @@ ck_spinlock_anderson_unlock(struct ck_spinlock_anderson *lock,
 }
 #endif /* CK_F_SPINLOCK_ANDERSON */
 #endif /* _CK_SPINLOCK_ANDERSON_H */
-
diff --git a/include/spinlock/cas.h b/include/spinlock/cas.h
index bda2bb3..ca087e3 100644
--- a/include/spinlock/cas.h
+++ b/include/spinlock/cas.h
@@ -118,4 +118,3 @@ CK_ELIDE_TRYLOCK_PROTOTYPE(ck_spinlock_cas, ck_spinlock_cas_t,
 
 #endif /* CK_F_SPINLOCK_CAS */
 #endif /* _CK_SPINLOCK_CAS_H */
-
diff --git a/include/spinlock/clh.h b/include/spinlock/clh.h
index 4252ec3..b066244 100644
--- a/include/spinlock/clh.h
+++ b/include/spinlock/clh.h
@@ -114,4 +114,3 @@ ck_spinlock_clh_unlock(struct ck_spinlock_clh **thread)
 }
 #endif /* CK_F_SPINLOCK_CLH */
 #endif /* _CK_SPINLOCK_CLH_H */
-
diff --git a/include/spinlock/dec.h b/include/spinlock/dec.h
index 350bbf2..35f44c1 100644
--- a/include/spinlock/dec.h
+++ b/include/spinlock/dec.h
@@ -140,4 +140,3 @@ CK_ELIDE_TRYLOCK_PROTOTYPE(ck_spinlock_dec, ck_spinlock_dec_t,
 
 #endif /* CK_F_SPINLOCK_DEC */
 #endif /* _CK_SPINLOCK_DEC_H */
-
diff --git a/include/spinlock/fas.h b/include/spinlock/fas.h
index 6886e35..1774919 100644
--- a/include/spinlock/fas.h
+++ b/include/spinlock/fas.h
@@ -115,4 +115,3 @@ CK_ELIDE_TRYLOCK_PROTOTYPE(ck_spinlock_fas, ck_spinlock_fas_t,
 
 #endif /* CK_F_SPINLOCK_FAS */
 #endif /* _CK_SPINLOCK_FAS_H */
-
diff --git a/include/spinlock/hclh.h b/include/spinlock/hclh.h
index dbae512..0838edb 100644
--- a/include/spinlock/hclh.h
+++ b/include/spinlock/hclh.h
@@ -142,4 +142,3 @@ ck_spinlock_hclh_unlock(struct ck_spinlock_hclh **thread)
 }
 #endif /* CK_F_SPINLOCK_HCLH */
 #endif /* _CK_SPINLOCK_HCLH_H */
-
diff --git a/include/spinlock/mcs.h b/include/spinlock/mcs.h
index 54cddca..f0d0e77 100644
--- a/include/spinlock/mcs.h
+++ b/include/spinlock/mcs.h
@@ -146,4 +146,3 @@ ck_spinlock_mcs_unlock(struct ck_spinlock_mcs **queue, struct ck_spinlock_mcs *n
 }
 #endif /* CK_F_SPINLOCK_MCS */
 #endif /* _CK_SPINLOCK_MCS_H */
-
diff --git a/include/spinlock/ticket.h b/include/spinlock/ticket.h
index 703feb7..de68851 100644
--- a/include/spinlock/ticket.h
+++ b/include/spinlock/ticket.h
@@ -295,4 +295,3 @@ CK_ELIDE_TRYLOCK_PROTOTYPE(ck_spinlock_ticket, ck_spinlock_ticket_t,
 
 #endif /* CK_F_SPINLOCK_TICKET */
 #endif /* _CK_SPINLOCK_TICKET_H */
-
diff --git a/src/ck_ht.c b/src/ck_ht.c
index 5e0e79d..80a3bfe 100644
--- a/src/ck_ht.c
+++ b/src/ck_ht.c
@@ -24,6 +24,7 @@
  * SUCH DAMAGE.
  */
 
+#define _CK_HT_IM
 #include <ck_ht.h>
 
 #ifdef CK_F_HT
@@ -451,6 +452,8 @@ ck_ht_gc(struct ck_ht *ht, unsigned long cycles, unsigned long seed)
 		offset = h.value & map->mask;
 
 		if (priority != NULL) {
+			ck_pr_store_64(&map->deletions, map->deletions + 1);
+			ck_pr_fence_store();
 #ifndef CK_HT_PP
 			ck_pr_store_64(&priority->key_length, entry->key_length);
 			ck_pr_store_64(&priority->hash, entry->hash);
@@ -463,8 +466,6 @@ ck_ht_gc(struct ck_ht *ht, unsigned long cycles, unsigned long seed)
 			ck_pr_fence_store();
 			ck_pr_store_ptr(&entry->key, (void *)CK_HT_KEY_TOMBSTONE);
 			ck_pr_fence_store();
-			ck_pr_store_64(&map->deletions, map->deletions + 1);
-			ck_pr_fence_store();
 		}
 
 		if (cycles == 0) {
@@ -768,29 +769,8 @@ ck_ht_remove_spmc(struct ck_ht *table,
 		return false;
 
 	*entry = snapshot;
-	ck_pr_store_ptr(&candidate->key, (void *)CK_HT_KEY_TOMBSTONE);
 
-	/*
-	 * It is possible that the key is read before transition into
-	 * the tombstone state. Assuming the keys do match, a reader
-	 * may have already acquired a snapshot of the value at the time.
-	 * However, assume the reader is preempted as a deletion occurs
-	 * followed by a replacement. In this case, it is possible that
-	 * the reader acquires some value V' instead of V. Let us assume
-	 * however that any transition from V into V' (essentially, update
-	 * of a value without the reader knowing of a K -> K' transition),
-	 * is preceded by an update to the deletions counter. This guarantees
-	 * any replacement of a T key also implies a D -> D' transition.
-	 * If D has not transitioned, the value has yet to be replaced so it
-	 * is a valid association with K and is safe to return. If D has
-	 * transitioned after a reader has acquired a snapshot then it is
-	 * possible that we are in the invalid state of (K, V'). The reader
-	 * is then able to attempt a reprobe at which point the only visible
-	 * states should be (T, V') or (K', V'). The latter is guaranteed
-	 * through memory fencing.
-	 */
-	ck_pr_fence_store();
-	ck_pr_store_64(&map->deletions, map->deletions + 1);
+	ck_pr_store_ptr(&candidate->key, (void *)CK_HT_KEY_TOMBSTONE);
 	ck_pr_fence_store();
 	ck_pr_store_64(&map->n_entries, map->n_entries - 1);
 	return true;
@@ -884,13 +864,11 @@ ck_ht_set_spmc(struct ck_ht *table,
 	if (candidate->key != CK_HT_KEY_EMPTY &&
 	    priority != NULL && candidate != priority) {
 		/*
-		 * If we are replacing an existing entry and an earlier
-		 * tombstone was found in the probe sequence then replace
-		 * the existing entry in a manner that doesn't affect linearizability
-		 * of concurrent get operations. We avoid a state of (K, B)
-		 * (where [K, B] -> [K', B]) by guaranteeing a forced reprobe
-		 * before transitioning from K to T. (K, B) implies (K, B, D')
-		 * so we will reprobe successfully from this transient state.
+		 * Entry is moved into another position in probe sequence.
+		 * We avoid a state of (K, B) (where [K, B] -> [K', B]) by
+		 * guaranteeing a forced reprobe before transitioning from K to
+		 * T. (K, B) implies (K, B, D') so we will reprobe successfully
+		 * from this transient state.
 		 */
 		probes = probes_wr;
 
@@ -898,28 +876,47 @@ ck_ht_set_spmc(struct ck_ht *table,
 		ck_pr_store_64(&priority->key_length, entry->key_length);
 		ck_pr_store_64(&priority->hash, entry->hash);
 #endif
+
+		/*
+		 * Readers must observe version counter change before they
+		 * observe re-use. If they observe re-use, it is at most
+		 * a tombstone.
+		 */
+		if (priority->value == CK_HT_KEY_TOMBSTONE) {
+			ck_pr_store_64(&map->deletions, map->deletions + 1);
+			ck_pr_fence_store();
+		}
+
 		ck_pr_store_ptr(&priority->value, (void *)entry->value);
 		ck_pr_fence_store();
 		ck_pr_store_ptr(&priority->key, (void *)entry->key);
 		ck_pr_fence_store();
+
+		/*
+		 * Make sure that readers who observe the tombstone would
+		 * also observe counter change.
+		 */
 		ck_pr_store_64(&map->deletions, map->deletions + 1);
 		ck_pr_fence_store();
+
 		ck_pr_store_ptr(&candidate->key, (void *)CK_HT_KEY_TOMBSTONE);
 		ck_pr_fence_store();
-		ck_pr_store_64(&map->deletions, map->deletions + 1);
-		ck_pr_fence_store();
 	} else {
 		/*
 		 * In this case we are inserting a new entry or replacing
-		 * an existing entry. There is no need to force a re-probe
-		 * on tombstone replacement due to the fact that previous
-		 * deletion counter update would have been published with
-		 * respect to any concurrent probes.
+		 * an existing entry. Yes, this can be combined into above branch,
+		 * but isn't because you are actually looking at dying code
+		 * (ck_ht is effectively deprecated and is being replaced soon).
 		 */
 		bool replace = candidate->key != CK_HT_KEY_EMPTY &&
 		    candidate->key != CK_HT_KEY_TOMBSTONE;
 
 		if (priority != NULL) {
+			if (priority->key == CK_HT_KEY_TOMBSTONE) {
+				ck_pr_store_64(&map->deletions, map->deletions + 1);
+				ck_pr_fence_store();
+			}
+
 			candidate = priority;
 			probes = probes_wr;
 		}
@@ -991,6 +988,10 @@ ck_ht_put_spmc(struct ck_ht *table,
 	}
 
 	if (priority != NULL) {
+		/* Version counter is updated before re-use. */
+		ck_pr_store_64(&map->deletions, map->deletions + 1);
+		ck_pr_fence_store();
+
 		/* Re-use tombstone if one was found. */
 		candidate = priority;
 		probes = probes_wr;