py: Add MICROPY_DYNAMIC_COMPILER option to config compiler at runtime.

This new compile-time option allows to make the bytecode compiler
configurable at runtime by setting the fields in the mp_dynamic_compiler
structure.  By using this feature, the compiler can generate bytecode
that targets any MicroPython runtime/VM, regardless of the host and
target compile-time settings.

Options so far that fall under this dynamic setting are:
- maximum number of bits that a small int can hold;
- whether caching of lookups is used in the bytecode;
- whether to use unicode strings or not (lexer behaviour differs, and
  therefore generated string constants differ).

1 files changed, 4 insertions, 0 deletions

diff --git a/py/mpstate.c b/py/mpstate.c
index 2ba3402ef..4fc8bc506 100644
--- a/py/mpstate.c
+++ b/py/mpstate.c
@@ -26,4 +26,8 @@
 
 #include "py/mpstate.h"
 
+#if MICROPY_DYNAMIC_COMPILER
+mp_dynamic_compiler_t mp_dynamic_compiler = {0};
+#endif
+
 mp_state_ctx_t mp_state_ctx;