py/dynruntime: Add support for float API to make/get floats.

We don't want to add a feature flag to .mpy files that indicate float
support because it will get complex and difficult to use.  Instead the .mpy
is built using whatever precision it chooses (float or double) and the
native glue API will convert between this choice and what the host runtime
actually uses.

py/dynruntime.h

@@ -190,4 +190,20 @@ static inline void mp_raise_OSError_dyn(int er) {
     nlr_raise(mp_call_function_n_kw(mp_load_global(MP_QSTR_OSError), 1, 0, &args[0]));
 }
 
+/******************************************************************************/
+// Floating point
+
+#define mp_obj_new_float_from_f(f)  (mp_fun_table.obj_new_float_from_f((f)))
+#define mp_obj_new_float_from_d(d)  (mp_fun_table.obj_new_float_from_d((d)))
+#define mp_obj_get_float_to_f(o)    (mp_fun_table.obj_get_float_to_f((o)))
+#define mp_obj_get_float_to_d(o)    (mp_fun_table.obj_get_float_to_d((o)))
+
+#if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_FLOAT
+#define mp_obj_new_float(f)         (mp_obj_new_float_from_f((f)))
+#define mp_obj_get_float(o)         (mp_obj_get_float_to_f((o)))
+#elif MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_DOUBLE
+#define mp_obj_new_float(f)         (mp_obj_new_float_from_d((f)))
+#define mp_obj_get_float(o)         (mp_obj_get_float_to_d((o)))
+#endif
+
 #endif // MICROPY_INCLUDED_PY_DYNRUNTIME_H

py/dynruntime.mk

@@ -46,6 +46,7 @@ ifeq ($(ARCH),x86)
 CROSS =
 CFLAGS += -m32 -fno-stack-protector
 MPY_CROSS_FLAGS += -mcache-lookup-bc
+MICROPY_FLOAT_IMPL ?= double
 
 else ifeq ($(ARCH),x64)
 
@@ -53,12 +54,14 @@ else ifeq ($(ARCH),x64)
 CROSS =
 CFLAGS += -fno-stack-protector
 MPY_CROSS_FLAGS += -mcache-lookup-bc
+MICROPY_FLOAT_IMPL ?= double
 
 else ifeq ($(ARCH),armv7m)
 
 # thumb
 CROSS = arm-none-eabi-
 CFLAGS += -mthumb -mcpu=cortex-m3
+MICROPY_FLOAT_IMPL ?= none
 
 else ifeq ($(ARCH),armv7emsp)
 
@@ -66,6 +69,7 @@ else ifeq ($(ARCH),armv7emsp)
 CROSS = arm-none-eabi-
 CFLAGS += -mthumb -mcpu=cortex-m4
 CFLAGS += -mfpu=fpv4-sp-d16 -mfloat-abi=hard
+MICROPY_FLOAT_IMPL ?= float
 
 else ifeq ($(ARCH),armv7emdp)
 
@@ -73,23 +77,29 @@ else ifeq ($(ARCH),armv7emdp)
 CROSS = arm-none-eabi-
 CFLAGS += -mthumb -mcpu=cortex-m7
 CFLAGS += -mfpu=fpv5-d16 -mfloat-abi=hard
+MICROPY_FLOAT_IMPL ?= double
 
 else ifeq ($(ARCH),xtensa)
 
 # xtensa
 CROSS = xtensa-lx106-elf-
 CFLAGS += -mforce-l32
+MICROPY_FLOAT_IMPL ?= none
 
 else ifeq ($(ARCH),xtensawin)
 
 # xtensawin
 CROSS = xtensa-esp32-elf-
 CFLAGS +=
+MICROPY_FLOAT_IMPL ?= float
 
 else
 $(error architecture '$(ARCH)' not supported)
 endif
 
+MICROPY_FLOAT_IMPL_UPPER = $(shell echo $(MICROPY_FLOAT_IMPL) | tr '[:lower:]' '[:upper:]')
+CFLAGS += -DMICROPY_FLOAT_IMPL=MICROPY_FLOAT_IMPL_$(MICROPY_FLOAT_IMPL_UPPER)
+
 CFLAGS += $(CFLAGS_EXTRA)
 
 ################################################################################

tools/mpy_ld.py

@@ -663,7 +663,7 @@ def link_objects(env, native_qstr_vals_len, native_qstr_objs_len):
 
     # Resolve unknown symbols
     mp_fun_table_sec = Section('.external.mp_fun_table', b'', 0)
-    fun_table = {key: 63 + idx
+    fun_table = {key: 67 + idx
         for idx, key in enumerate([
             'mp_type_type',
             'mp_type_str',