Revert "Let compiler decide how to unroll"

This reverts commit fdc6797ea6f3865ca079ebc260814a6f584b1cff.

src/encode.c

@@ -278,6 +278,33 @@ static void preprocess_signed(struct aec_stream *strm)
     state->uncomp_len = (strm->block_size - 1) * strm->bits_per_sample;
 }
 
+static uint64_t block_fs(struct aec_stream *strm, int k)
+{
+    /**
+       Sum FS of all samples in block for given splitting position.
+    */
+
+    int i;
+    uint64_t fs = 0;
+    struct internal_state *state = strm->state;
+
+    for (i = 0; i < strm->block_size; i += 8)
+        fs +=
+            (uint64_t)(state->block[i + 0] >> k)
+            + (uint64_t)(state->block[i + 1] >> k)
+            + (uint64_t)(state->block[i + 2] >> k)
+            + (uint64_t)(state->block[i + 3] >> k)
+            + (uint64_t)(state->block[i + 4] >> k)
+            + (uint64_t)(state->block[i + 5] >> k)
+            + (uint64_t)(state->block[i + 6] >> k)
+            + (uint64_t)(state->block[i + 7] >> k);
+
+    if (state->ref)
+        fs -= (uint64_t)(state->block[0] >> k);
+
+    return fs;
+}
+
 static uint32_t assess_splitting_option(struct aec_stream *strm)
 {
     /**
@@ -305,7 +332,7 @@ static uint32_t assess_splitting_option(struct aec_stream *strm)
        analogue check can be done for decreasing k.
      */
 
-    int i, k;
+    int k;
     int k_min;
     int this_bs; /* Block size of current block */
     int no_turn; /* 1 if we shouldn't reverse */
@@ -323,9 +350,7 @@ static uint32_t assess_splitting_option(struct aec_stream *strm)
     dir = 1;
 
     for (;;) {
-        fs_len = 0;
-        for (i = state->ref; i < strm->block_size; i++)
-            fs_len += (uint64_t)(state->block[i] >> k);
+        fs_len = block_fs(strm, k);
         len = fs_len + this_bs * (k + 1);
 
         if (len < len_min) {