py: Add MICROPY_COMP_{DOUBLE,TRIPLE}_TUPLE_ASSIGN config options.

These allow to fine-tune the compiler to select whether it optimises
tuple assignments of the form a, b = c, d and a, b, c = d, e, f.
Sensible defaults are provided.

bare-arm/mpconfigport.h

@@ -8,6 +8,8 @@
 #define MICROPY_EMIT_INLINE_THUMB   (0)
 #define MICROPY_COMP_MODULE_CONST   (0)
 #define MICROPY_COMP_CONST          (0)
+#define MICROPY_COMP_DOUBLE_TUPLE_ASSIGN (0)
+#define MICROPY_COMP_TRIPLE_TUPLE_ASSIGN (0)
 #define MICROPY_MEM_STATS           (0)
 #define MICROPY_DEBUG_PRINTERS      (0)
 #define MICROPY_ENABLE_GC           (0)

minimal/mpconfigport.h

@@ -8,6 +8,8 @@
 #define MICROPY_EMIT_INLINE_THUMB   (0)
 #define MICROPY_COMP_MODULE_CONST   (0)
 #define MICROPY_COMP_CONST          (0)
+#define MICROPY_COMP_DOUBLE_TUPLE_ASSIGN (0)
+#define MICROPY_COMP_TRIPLE_TUPLE_ASSIGN (0)
 #define MICROPY_MEM_STATS           (0)
 #define MICROPY_DEBUG_PRINTERS      (0)
 #define MICROPY_ENABLE_GC           (1)

py/compile.c

@@ -2165,7 +2165,8 @@ STATIC void compile_expr_stmt(compiler_t *comp, mp_parse_node_struct_t *pns) {
             }
         } else {
             assert(kind == PN_expr_stmt_assign); // should be
-            if (MP_PARSE_NODE_IS_STRUCT_KIND(pns1->nodes[0], PN_testlist_star_expr)
+            if (MICROPY_COMP_DOUBLE_TUPLE_ASSIGN
+                && MP_PARSE_NODE_IS_STRUCT_KIND(pns1->nodes[0], PN_testlist_star_expr)
                 && MP_PARSE_NODE_IS_STRUCT_KIND(pns->nodes[0], PN_testlist_star_expr)
                 && MP_PARSE_NODE_STRUCT_NUM_NODES((mp_parse_node_struct_t*)pns1->nodes[0]) == 2
                 && MP_PARSE_NODE_STRUCT_NUM_NODES((mp_parse_node_struct_t*)pns->nodes[0]) == 2) {
@@ -2182,7 +2183,8 @@ STATIC void compile_expr_stmt(compiler_t *comp, mp_parse_node_struct_t *pns) {
                 EMIT(rot_two);
                 c_assign(comp, pns0->nodes[0], ASSIGN_STORE); // lhs store
                 c_assign(comp, pns0->nodes[1], ASSIGN_STORE); // lhs store
-            } else if (MP_PARSE_NODE_IS_STRUCT_KIND(pns1->nodes[0], PN_testlist_star_expr)
+            } else if (MICROPY_COMP_TRIPLE_TUPLE_ASSIGN
+                && MP_PARSE_NODE_IS_STRUCT_KIND(pns1->nodes[0], PN_testlist_star_expr)
                 && MP_PARSE_NODE_IS_STRUCT_KIND(pns->nodes[0], PN_testlist_star_expr)
                 && MP_PARSE_NODE_STRUCT_NUM_NODES((mp_parse_node_struct_t*)pns1->nodes[0]) == 3
                 && MP_PARSE_NODE_STRUCT_NUM_NODES((mp_parse_node_struct_t*)pns->nodes[0]) == 3) {

py/mpconfig.h

@@ -175,6 +175,18 @@
 #define MICROPY_COMP_CONST (1)
 #endif
 
+// Whether to enable optimisation of: a, b = c, d
+// Costs 124 bytes (Thumb2)
+#ifndef MICROPY_COMP_DOUBLE_TUPLE_ASSIGN
+#define MICROPY_COMP_DOUBLE_TUPLE_ASSIGN (1)
+#endif
+
+// Whether to enable optimisation of: a, b, c = d, e, f
+// Cost 156 bytes (Thumb2)
+#ifndef MICROPY_COMP_TRIPLE_TUPLE_ASSIGN
+#define MICROPY_COMP_TRIPLE_TUPLE_ASSIGN (0)
+#endif
+
 /*****************************************************************************/
 /* Internal debugging stuff                                                  */
 

stmhal/mpconfigport.h

@@ -34,6 +34,7 @@
 #define MICROPY_EMIT_THUMB          (1)
 #define MICROPY_EMIT_INLINE_THUMB   (1)
 #define MICROPY_COMP_MODULE_CONST   (1)
+#define MICROPY_COMP_TRIPLE_TUPLE_ASSIGN (1)
 #define MICROPY_ENABLE_GC           (1)
 #define MICROPY_ENABLE_FINALISER    (1)
 #define MICROPY_STACK_CHECK         (1)

unix-cpy/mpconfigport.h

@@ -27,6 +27,7 @@
 // options to control how Micro Python is built
 
 #define MICROPY_EMIT_CPYTHON        (1)
+#define MICROPY_COMP_TRIPLE_TUPLE_ASSIGN (1)
 #define MICROPY_HELPER_LEXER_UNIX   (1)
 #define MICROPY_FLOAT_IMPL          (MICROPY_FLOAT_IMPL_DOUBLE)
 #define MICROPY_PY_IO               (0)

unix/mpconfigport.h

@@ -40,6 +40,7 @@
     #define MICROPY_EMIT_ARM        (1)
 #endif
 #define MICROPY_COMP_MODULE_CONST   (1)
+#define MICROPY_COMP_TRIPLE_TUPLE_ASSIGN (1)
 #define MICROPY_ENABLE_GC           (1)
 #define MICROPY_ENABLE_FINALISER    (1)
 #define MICROPY_STACK_CHECK         (1)

windows/mpconfigport.h

@@ -36,6 +36,7 @@
 #define MICROPY_EMIT_THUMB          (0)
 #define MICROPY_EMIT_INLINE_THUMB   (0)
 #define MICROPY_COMP_MODULE_CONST   (1)
+#define MICROPY_COMP_TRIPLE_TUPLE_ASSIGN (1)
 #define MICROPY_ENABLE_GC           (1)
 #define MICROPY_ENABLE_FINALISER    (1)
 #define MICROPY_STACK_CHECK         (1)