stm32: Disable computed goto on constrained boards.

Saves ~1kiB.  Add comment to this effect to mpconfig.h.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>

ports/stm32/boards/B_L072Z_LRWAN1/mpconfigboard.h

@@ -7,6 +7,7 @@
 
 #define MICROPY_EMIT_THUMB          (0)
 #define MICROPY_EMIT_INLINE_THUMB   (0)
+#define MICROPY_OPT_COMPUTED_GOTO   (0)
 #define MICROPY_PY_BUILTINS_COMPLEX (0)
 #define MICROPY_PY_GENERATOR_PEND_THROW (0)
 #define MICROPY_PY_MATH             (0)

ports/stm32/boards/NUCLEO_F091RC/mpconfigboard.h

@@ -3,6 +3,7 @@
 
 #define MICROPY_EMIT_THUMB          (0)
 #define MICROPY_EMIT_INLINE_THUMB   (0)
+#define MICROPY_OPT_COMPUTED_GOTO   (0)
 #define MICROPY_PY_USOCKET          (0)
 #define MICROPY_PY_NETWORK          (0)
 #define MICROPY_PY_STM              (0)

ports/stm32/boards/NUCLEO_L073RZ/mpconfigboard.h

@@ -7,6 +7,7 @@
 
 #define MICROPY_EMIT_THUMB          (0)
 #define MICROPY_EMIT_INLINE_THUMB   (0)
+#define MICROPY_OPT_COMPUTED_GOTO   (0)
 #define MICROPY_PY_BUILTINS_COMPLEX (0)
 #define MICROPY_PY_GENERATOR_PEND_THROW (0)
 #define MICROPY_PY_MATH             (0)

ports/stm32/mpconfigport.h

@@ -56,7 +56,9 @@
 #define MICROPY_COMP_RETURN_IF_EXPR (1)
 
 // optimisations
+#ifndef MICROPY_OPT_COMPUTED_GOTO
 #define MICROPY_OPT_COMPUTED_GOTO   (1)
+#endif
 #define MICROPY_OPT_CACHE_MAP_LOOKUP_IN_BYTECODE (0)
 #define MICROPY_OPT_MPZ_BITWISE     (1)
 #define MICROPY_OPT_MATH_FACTORIAL  (1)

py/mpconfig.h

@@ -483,7 +483,8 @@
 /* Optimisations                                                             */
 
 // Whether to use computed gotos in the VM, or a switch
-// Computed gotos are roughly 10% faster, and increase VM code size by a little
+// Computed gotos are roughly 10% faster, and increase VM code size by a little,
+// e.g. ~1kiB on Cortex M4.
 // Note: enabling this will use the gcc-specific extensions of ranged designated
 // initialisers and addresses of labels, which are not part of the C99 standard.
 #ifndef MICROPY_OPT_COMPUTED_GOTO