One weird trick: set a bogus error value in the parser impl

This makes us faster under both gcc and clang somehow.

include/simdjson/internal/dom_parser_implementation.h

@@ -136,6 +136,9 @@ public:
   /** Return address of each open { or [ */
   std::unique_ptr<internal::ret_address[]> ret_address{};
 
+  /** Error code, used ENTIRELY to make gcc not be slower than before. Not actually consumed. */
+  error_code error{UNINITIALIZED};
+
   /**
    * The largest document this parser can support without reallocating.
    *

src/generic/stage2/streaming_structural_parser.h

@@ -12,7 +12,7 @@ struct streaming_structural_parser: structural_parser {
     advance_char();
     // Push the root scope (there is always at least one scope)
     if (start_document(finish_parser)) {
-      return DEPTH_ERROR;
+      return parser.error = DEPTH_ERROR;
     }
     return SUCCESS;
   }
@@ -21,16 +21,16 @@ struct streaming_structural_parser: structural_parser {
   WARN_UNUSED really_inline error_code finish() {
     if ( structurals.past_end(parser.n_structural_indexes) ) {
       log_error("IMPOSSIBLE: past the end of the JSON!");
-      return TAPE_ERROR;
+      return parser.error = TAPE_ERROR;
     }
     end_document();
     if (depth != 0) {
       log_error("Unclosed objects or arrays!");
-      return TAPE_ERROR;
+      return parser.error = TAPE_ERROR;
     }
     if (parser.containing_scope[depth].tape_index != 0) {
       log_error("IMPOSSIBLE: root scope tape index did not start at 0!");
-      return TAPE_ERROR;
+      return parser.error = TAPE_ERROR;
     }
     bool finished = structurals.at_end(parser.n_structural_indexes);
     if (!finished) { log_value("(and has more)"); }

src/generic/stage2/structural_parser.h

@@ -272,16 +272,16 @@ struct structural_parser {
     // the string might not be NULL terminated.
     if ( !structurals.at_end(parser.n_structural_indexes) ) {
       log_error("More than one JSON value at the root of the document, or extra characters at the end of the JSON!");
-      return TAPE_ERROR;
+      return parser.error = TAPE_ERROR;
     }
     end_document();
     if (depth != 0) {
       log_error("Unclosed objects or arrays!");
-      return TAPE_ERROR;
+      return parser.error = TAPE_ERROR;
     }
     if (parser.containing_scope[depth].tape_index != 0) {
       log_error("IMPOSSIBLE: root scope tape index did not start at 0!");
-      return TAPE_ERROR;
+      return parser.error = TAPE_ERROR;
     }
 
     return SUCCESS;
@@ -299,11 +299,11 @@ struct structural_parser {
     * carefully,
     * all without any added cost. */
     if (depth >= parser.max_depth()) {
-      return DEPTH_ERROR;
+      return parser.error = DEPTH_ERROR;
     }
     switch (structurals.current_char()) {
     case '"':
-      return STRING_ERROR;
+      return parser.error = STRING_ERROR;
     case '0':
     case '1':
     case '2':
@@ -315,34 +315,35 @@ struct structural_parser {
     case '8':
     case '9':
     case '-':
-      return NUMBER_ERROR;
+      return parser.error = NUMBER_ERROR;
     case 't':
-      return T_ATOM_ERROR;
+      return parser.error = T_ATOM_ERROR;
     case 'n':
-      return N_ATOM_ERROR;
+      return parser.error = N_ATOM_ERROR;
     case 'f':
-      return F_ATOM_ERROR;
+      return parser.error = F_ATOM_ERROR;
     default:
-      return TAPE_ERROR;
+      return parser.error = TAPE_ERROR;
     }
   }
 
   really_inline void init() {
     current_string_buf_loc = parser.doc->string_buf.get();
     parser.current_loc = 0;
+    parser.error = UNINITIALIZED;
   }
 
   WARN_UNUSED really_inline error_code start(size_t len, ret_address finish_state) {
     log_start();
     init(); // sets is_valid to false
     if (len > parser.capacity()) {
-      return CAPACITY;
+      return parser.error = CAPACITY;
     }
     // Advance to the first character as soon as possible
     structurals.advance_char();
     // Push the root scope (there is always at least one scope)
     if (start_document(finish_state)) {
-      return DEPTH_ERROR;
+      return parser.error = DEPTH_ERROR;
     }
     return SUCCESS;
   }