py/emitinlinextensa: Simplify register name lookup.

This commit changes the Xtensa inline assembly parser to use a slightly
simpler (and probably a tiny bit more efficient) way to look up register
names when decoding instruction parameters.

Signed-off-by: Alessandro Gatti <[email protected]>

Author: agatti

py/emitinlinextensa.c

@@ -115,50 +115,21 @@ static bool emit_inline_xtensa_label(emit_inline_asm_t *emit, mp_uint_t label_nu
     return true;
 }
 
-typedef struct _reg_name_t { byte reg;
-                             byte name[3];
-} reg_name_t;
-static const reg_name_t reg_name_table[] = {
-    {0, "a0\0"},
-    {1, "a1\0"},
-    {2, "a2\0"},
-    {3, "a3\0"},
-    {4, "a4\0"},
-    {5, "a5\0"},
-    {6, "a6\0"},
-    {7, "a7\0"},
-    {8, "a8\0"},
-    {9, "a9\0"},
-    {10, "a10"},
-    {11, "a11"},
-    {12, "a12"},
-    {13, "a13"},
-    {14, "a14"},
-    {15, "a15"},
+static const qstr_short_t REGISTERS[16] = {
+    MP_QSTR_a0, MP_QSTR_a1, MP_QSTR_a2, MP_QSTR_a3, MP_QSTR_a4, MP_QSTR_a5, MP_QSTR_a6, MP_QSTR_a7,
+    MP_QSTR_a8, MP_QSTR_a9, MP_QSTR_a10, MP_QSTR_a11, MP_QSTR_a12, MP_QSTR_a13, MP_QSTR_a14, MP_QSTR_a15
 };
 
-// return empty string in case of error, so we can attempt to parse the string
-// without a special check if it was in fact a string
-static const char *get_arg_str(mp_parse_node_t pn) {
-    if (MP_PARSE_NODE_IS_ID(pn)) {
-        qstr qst = MP_PARSE_NODE_LEAF_ARG(pn);
-        return qstr_str(qst);
-    } else {
-        return "";
-    }
-}
-
 static mp_uint_t get_arg_reg(emit_inline_asm_t *emit, const char *op, mp_parse_node_t pn) {
-    const char *reg_str = get_arg_str(pn);
-    for (mp_uint_t i = 0; i < MP_ARRAY_SIZE(reg_name_table); i++) {
-        const reg_name_t *r = &reg_name_table[i];
-        if (reg_str[0] == r->name[0]
-            && reg_str[1] == r->name[1]
-            && reg_str[2] == r->name[2]
-            && (reg_str[2] == '\0' || reg_str[3] == '\0')) {
-            return r->reg;
+    if (MP_PARSE_NODE_IS_ID(pn)) {
+        qstr node_qstr = MP_PARSE_NODE_LEAF_ARG(pn);
+        for (size_t i = 0; i < MP_ARRAY_SIZE(REGISTERS); i++) {
+            if (node_qstr == REGISTERS[i]) {
+                return i;
+            }
         }
     }
+
     emit_inline_xtensa_error_exc(emit,
         mp_obj_new_exception_msg_varg(&mp_type_SyntaxError,
             MP_ERROR_TEXT("'%s' expects a register"), op));