py/grammar: Group no-compile grammar rules together to shrink tables.

Grammar rules have 2 variants: ones that are attached to a specific
compile function which is called to compile that grammar node, and ones
that don't have a compile function and are instead just inspected to see
what form they take.

In the compiler there is a table of all grammar rules, with each entry
having a pointer to the associated compile function.  Those rules with no
compile function have a null pointer.  There are 120 such rules, so that's
120 words of essentially wasted code space.

By grouping together the compile vs no-compile rules we can put all the
no-compile rules at the end of the list of rules, and then we don't need
to store the null pointers.  We just have a truncated table and it's
guaranteed that when indexing this table we only index the first half,
the half with populated pointers.

This patch implements such a grouping by having a specific macro for the
compile vs no-compile grammar rules (DEF_RULE vs DEF_RULE_NC).  It saves
around 460 bytes of code on 32-bit archs.

1 files changed, 12 insertions, 1 deletions

diff --git a/py/emitinlinethumb.c b/py/emitinlinethumb.c
index 406272813..89bcebfea 100644
--- a/py/emitinlinethumb.c
+++ b/py/emitinlinethumb.c
@@ -36,10 +36,21 @@
 #if MICROPY_EMIT_INLINE_THUMB
 
 typedef enum {
+// define rules with a compile function
 #define DEF_RULE(rule, comp, kind, ...) PN_##rule,
+#define DEF_RULE_NC(rule, kind, ...)
 #include "py/grammar.h"
 #undef DEF_RULE
-    PN_maximum_number_of,
+#undef DEF_RULE_NC
+    PN_string, // special node for non-interned string
+    PN_bytes, // special node for non-interned bytes
+    PN_const_object, // special node for a constant, generic Python object
+// define rules without a compile function
+#define DEF_RULE(rule, comp, kind, ...)
+#define DEF_RULE_NC(rule, kind, ...) PN_##rule,
+#include "py/grammar.h"
+#undef DEF_RULE
+#undef DEF_RULE_NC
 } pn_kind_t;
 
 struct _emit_inline_asm_t {