Enable shared_dictionary for quality 3 and 4.

PiperOrigin-RevId: 843477953

c/enc/backward_references.c

@@ -131,6 +131,14 @@ static BROTLI_INLINE size_t ComputeDistanceCode(size_t distance,
 #define PREFIX() D
 #define ENABLE_COMPOUND_DICTIONARY 1
 
+#define HASHER() H3
+/* NOLINTNEXTLINE(build/include) */
+#include "backward_references_inc.h"
+#undef HASHER
+#define HASHER() H4
+/* NOLINTNEXTLINE(build/include) */
+#include "backward_references_inc.h"
+#undef HASHER
 #define HASHER() H5
 /* NOLINTNEXTLINE(build/include) */
 #include "backward_references_inc.h"
@@ -192,6 +200,8 @@ void BrotliCreateBackwardReferences(size_t num_bytes,
             literal_context_lut, params, hasher, dist_cache,        \
             last_insert_len, commands, num_commands, num_literals); \
         return;
+      CASE_(3)
+      CASE_(4)
       CASE_(5)
       CASE_(6)
 #if defined(BROTLI_MAX_SIMD_QUALITY)

c/enc/hash_longest_match_quickly_inc.h

@@ -168,7 +168,7 @@ static BROTLI_INLINE void FN(FindLongestMatch)(
   BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask + 1);
 
   out->len_code_delta = 0;
-  if (prev_ix < cur_ix) {
+  if (prev_ix < cur_ix && cached_backward <= max_backward) {
     prev_ix &= (uint32_t)ring_buffer_mask;
     if (compare_char == data[prev_ix + best_len]) {
       const size_t len = FindMatchLengthWithLimit(