Enable squeezing property storage in flash

.. and enable it on atmel-samd and raspberrypi. On trinket_m0 this saves
96 net bytes of flash. There are 216 bytes actually saved by reducing
the flash storage size of the property descriptors, but added code in
several paths takes back over half of the 'raw savings'.

By organizing the "get-only" and "get-set" (but no delete) properties
each in a different section, we can represent then more efficiently.

Testing performed: that a get-only property can still be gotten but
can't be set or deleted; that a get-set property can sill be gotten or
set but can't be deleted.  Tested on pygamer.

Because this requires linker file support, I only enabled it on two of
the ports.

Author: jepler

ports/atmel-samd/boards/common.template.ld

@@ -28,6 +28,13 @@ SECTIONS
         _sfixed = .;
         KEEP(*(.vectors)) /* isr vector table */
 
+        __property_getter_start = .;
+        *(.property_getter)
+        __property_getter_end = .;
+        __property_getset_start = .;
+        *(.property_getset)
+        __property_getset_end = .;
+
         /* Sort text sections so that they have fewer *fill* bytes needed. */
         *(SORT_BY_ALIGNMENT(SORT_BY_NAME(.text)))           /* .text sections (code) */
         *(SORT_BY_ALIGNMENT(SORT_BY_NAME(.text*)))          /* .text* sections (code) */

ports/atmel-samd/mpconfigport.mk

@@ -8,6 +8,7 @@ INTERNAL_LIBM = 1
 USB_NUM_ENDPOINT_PAIRS = 8
 
 CIRCUITPY_ROTARYIO_SOFTENCODER = 1
+CIRCUITPY_OPTIMIZE_PROPERTY_FLASH_SIZE ?= 1
 
 ######################################################################
 # Put samd21-only choices here.

ports/raspberrypi/link.ld

@@ -68,6 +68,14 @@ SECTIONS
         /* bit of a hack right now to exclude all floating point and time critical (e.g. memset, memcpy) code from
          * FLASH ... we will include any thing excluded here in .data below by default */
         *(.init)
+
+        __property_getter_start = .;
+        *(.property_getter)
+        __property_getter_end = .;
+        __property_getset_start = .;
+        *(.property_getset)
+        __property_getset_end = .;
+
         *(EXCLUDE_FILE(*libgcc.a: *libc.a:*lib_a-mem*.o *libm.a:) .text*)
         *(.fini)
         /* Pull all c'tors into .text */

ports/raspberrypi/mpconfigport.mk

@@ -1,6 +1,7 @@
 # All raspberrypi ports have longints.
 LONGINT_IMPL = MPZ
 
+CIRCUITPY_OPTIMIZE_PROPERTY_FLASH_SIZE ?= 1
 CIRCUITPY_ALARM ?= 1
 
 CIRCUITPY_RP2PIO ?= 1

py/circuitpy_mpconfig.h

@@ -573,4 +573,6 @@ void supervisor_run_background_tasks_if_tick(void);
 #define MICROPY_WRAP_MP_EXECUTE_BYTECODE PLACE_IN_ITCM
 #endif
 
+#define MICROPY_PY_OPTIMIZE_PROPERTY_FLASH_SIZE (CIRCUITPY_OPTIMIZE_PROPERTY_FLASH_SIZE)
+
 #endif  // __INCLUDED_MPCONFIG_CIRCUITPY_H

py/circuitpy_mpconfig.mk

@@ -32,6 +32,11 @@
 CIRCUITPY_FULL_BUILD ?= 1
 CFLAGS += -DCIRCUITPY_FULL_BUILD=$(CIRCUITPY_FULL_BUILD)
 
+# Reduce the size of in-flash properties. Requires support in the .ld linker
+# file, so not enabled by default.
+CIRCUITPY_OPTIMIZE_PROPERTY_FLASH_SIZE ?= 0
+CFLAGS += -DCIRCUITPY_OPTIMIZE_PROPERTY_FLASH_SIZE=$(CIRCUITPY_OPTIMIZE_PROPERTY_FLASH_SIZE)
+
 # async/await language keyword support
 MICROPY_PY_ASYNC_AWAIT ?= $(CIRCUITPY_FULL_BUILD)
 CFLAGS += -DMICROPY_PY_ASYNC_AWAIT=$(MICROPY_PY_ASYNC_AWAIT)

py/mpconfig.h

@@ -1078,6 +1078,11 @@ typedef double mp_float_t;
 #define MICROPY_PY_BUILTINS_PROPERTY (MICROPY_CONFIG_ROM_LEVEL_AT_LEAST_CORE_FEATURES)
 #endif
 
+// Whether to optimize property flash storage size (requires linker script support)
+#ifndef MICROPY_PY_BUILTINS_PROPERTY
+#define MICROPY_PY_BUILTINS_PROPERTY (0)
+#endif
+
 // Whether to implement the start/stop/step attributes (readback) on
 // the "range" builtin type. Rarely used, and costs ~60 bytes (x86).
 #ifndef MICROPY_PY_BUILTINS_RANGE_ATTRS

py/objproperty.c

@@ -95,9 +95,24 @@ const mp_obj_type_t mp_type_property = {
     .locals_dict = (mp_obj_dict_t *)&property_locals_dict,
 };
 
-const mp_obj_t *mp_obj_property_get(mp_obj_t self_in) {
+#if MICROPY_PY_OPTIMIZE_PROPERTY_FLASH_SIZE
+extern const mp_obj_property_t __property_getter_start, __property_getter_end, __property_getset_start, __property_getset_end;
+#endif
+
+const mp_obj_t *mp_obj_property_get(mp_obj_t self_in, size_t *n_proxy) {
     mp_check_self(mp_obj_is_type(self_in, &mp_type_property));
     mp_obj_property_t *self = MP_OBJ_TO_PTR(self_in);
+    #if MICROPY_PY_OPTIMIZE_PROPERTY_FLASH_SIZE
+    if (self >= &__property_getter_start && self < &__property_getter_end) {
+        *n_proxy = 1;
+    } else if (self >= &__property_getset_start && self < &__property_getset_end) {
+        *n_proxy = 2;
+    } else {
+        *n_proxy = 3;
+    }
+    #else
+    *n_proxy = 3;
+    #endif
     return self->proxy;
 }
 

py/objproperty.h

@@ -35,11 +35,27 @@ typedef struct _mp_obj_property_t {
     mp_obj_t proxy[3]; // getter, setter, deleter
 } mp_obj_property_t;
 
+#if MICROPY_PY_OPTIMIZE_PROPERTY_FLASH_SIZE
+typedef struct _mp_obj_property_getter_t {
+    mp_obj_base_t base;
+    mp_obj_t proxy[1]; // getter
+} mp_obj_property_getter_t;
+
+typedef struct _mp_obj_property_getset_t {
+    mp_obj_base_t base;
+    mp_obj_t proxy[2]; // getter, setter
+} mp_obj_property_getset_t;
+
+#define MP_PROPERTY_GETTER(P, G) const mp_obj_property_getter_t P __attribute((section(".property_getter"))) = {.base.type = &mp_type_property, .proxy = {G}}
+#define MP_PROPERTY_GETSET(P, G, S) const mp_obj_property_getset_t P __attribute((section(".property_getset"))) = {.base.type = &mp_type_property, .proxy = {G, S}}
+
+#else
 typedef struct _mp_obj_property_t mp_obj_property_getter_t;
 typedef struct _mp_obj_property_t mp_obj_property_getset_t;
 
 #define MP_PROPERTY_GETTER(P, G) const mp_obj_property_t P = {.base.type = &mp_type_property, .proxy = {G, MP_ROM_NONE, MP_ROM_NONE}}
 #define MP_PROPERTY_GETSET(P, G, S) const mp_obj_property_t P = {.base.type = &mp_type_property, .proxy = {G, S, MP_ROM_NONE}}
+#endif
 
 #endif  // MICROPY_PY_BUILTINS_PROPERTY
 

py/objtype.c

@@ -660,7 +660,8 @@ STATIC void mp_obj_instance_load_attr(mp_obj_t self_in, qstr attr, mp_obj_t *des
             // be called by the descriptor code down below.  But that way
             // requires overhead for the nested mp_call's and overhead for
             // the code.
-            const mp_obj_t *proxy = mp_obj_property_get(member);
+            size_t n_proxy;
+            const mp_obj_t *proxy = mp_obj_property_get(member, &n_proxy);
             if (proxy[0] == mp_const_none) {
                 mp_raise_AttributeError(MP_ERROR_TEXT("unreadable attribute"));
             } else {
@@ -740,11 +741,12 @@ STATIC bool mp_obj_instance_store_attr(mp_obj_t self_in, qstr attr, mp_obj_t val
             // would be called by the descriptor code down below.  But that way
             // requires overhead for the nested mp_call's and overhead for
             // the code.
-            const mp_obj_t *proxy = mp_obj_property_get(member[0]);
+            size_t n_proxy;
+            const mp_obj_t *proxy = mp_obj_property_get(member[0], &n_proxy);
             mp_obj_t dest[2] = {self_in, value};
             if (value == MP_OBJ_NULL) {
                 // delete attribute
-                if (proxy[2] == mp_const_none) {
+                if (n_proxy < 3 || proxy[2] == mp_const_none) {
                     // TODO better error message?
                     return false;
                 } else {
@@ -753,7 +755,7 @@ STATIC bool mp_obj_instance_store_attr(mp_obj_t self_in, qstr attr, mp_obj_t val
                 }
             } else {
                 // store attribute
-                if (proxy[1] == mp_const_none) {
+                if (n_proxy < 2 || proxy[1] == mp_const_none) {
                     // TODO better error message?
                     return false;
                 } else {
@@ -1374,7 +1376,8 @@ STATIC void super_attr(mp_obj_t self_in, qstr attr, mp_obj_t *dest) {
             // here...
             #if MICROPY_PY_BUILTINS_PROPERTY
             if (mp_obj_is_type(member, &mp_type_property)) {
-                const mp_obj_t *proxy = mp_obj_property_get(member);
+                size_t n_proxy;
+                const mp_obj_t *proxy = mp_obj_property_get(member, &n_proxy);
                 if (proxy[0] == mp_const_none) {
                     mp_raise_AttributeError(MP_ERROR_TEXT("unreadable attribute"));
                 } else {