CLJS-1876: Faster reduce for PV, Subvec and ChunkedSeq

Author: thomasmulvaney

src/main/cljs/cljs/core.cljs

@@ -5016,6 +5016,22 @@ reduces them without incurring seq initialization"
         (unchecked-array-for v i))
       v start end)))
 
+(defn- pv-reduce
+  ([pv f start end]
+   (if (< start end)
+     (pv-reduce pv f (nth pv start) (inc start) end)
+     (f)))
+  ([pv f init start end]
+   (loop [acc init i start arr (unchecked-array-for pv start)]
+     (if (< i end)
+       (let [j (bit-and i 0x01f)
+             arr (if (zero? j) (unchecked-array-for pv i) arr)
+             nacc (f acc (aget arr j))]
+         (if (reduced? nacc)
+           @nacc
+           (recur nacc (inc i) arr)))
+       acc))))
+
 (declare tv-editable-root tv-editable-tail TransientVector deref
          pr-sequential-writer pr-writer chunked-seq)
 
@@ -5162,7 +5178,7 @@ reduces them without incurring seq initialization"
 
   IReduce
   (-reduce [v f]
-    (ci-reduce v f))
+    (pv-reduce v f 0 cnt))
   (-reduce [v f init]
     (loop [i 0 init init]
       (if (< i cnt)
@@ -5334,10 +5350,10 @@ reduces them without incurring seq initialization"
 
   IReduce
   (-reduce [coll f]
-    (ci-reduce (subvec vec (+ i off) (count vec)) f))
+    (pv-reduce vec f (+ i off) (count vec)))
 
   (-reduce [coll f start]
-    (ci-reduce (subvec vec (+ i off) (count vec)) f start)))
+    (pv-reduce vec f start (+ i off) (count vec))))
 
 (es6-iterable ChunkedSeq)
 
@@ -5447,9 +5463,9 @@ reduces them without incurring seq initialization"
 
   IReduce
   (-reduce [coll f]
-    (ci-reduce coll f))
-  (-reduce [coll f start]
-    (ci-reduce coll f start))
+    (pv-reduce v f start end))
+  (-reduce [coll f init]
+    (pv-reduce v f init start end))
 
   IKVReduce
   (-kv-reduce [coll f init]