py/obj.h: Redefine qstr object encoding to add immediate obj encoding.

This commit adjusts the definition of qstr encoding in all object
representations by taking a single bit from the qstr space and using it to
distinguish between qstrs and a new kind of literal object: immediate
objects.  In other words, the qstr space is divided in two pieces, one half
for qstrs and the other half for immediate objects.

There is still enough room for qstr values (29 bits in representation A on
a 32-bit architecture, and 19 bits in representation C) and the new
immediate objects can be used for things like None, False and True.

py/mpconfig.h

@@ -70,25 +70,28 @@
 
 // A MicroPython object is a machine word having the following form:
 //  - xxxx...xxx1 : a small int, bits 1 and above are the value
-//  - xxxx...xx10 : a qstr, bits 2 and above are the value
+//  - xxxx...x010 : a qstr, bits 3 and above are the value
+//  - xxxx...x110 : an immediate object, bits 3 and above are the value
 //  - xxxx...xx00 : a pointer to an mp_obj_base_t (unless a fake object)
 #define MICROPY_OBJ_REPR_A (0)
 
 // A MicroPython object is a machine word having the following form:
 //  - xxxx...xx01 : a small int, bits 2 and above are the value
-//  - xxxx...xx11 : a qstr, bits 2 and above are the value
+//  - xxxx...x011 : a qstr, bits 3 and above are the value
+//  - xxxx...x111 : an immediate object, bits 3 and above are the value
 //  - xxxx...xxx0 : a pointer to an mp_obj_base_t (unless a fake object)
 #define MICROPY_OBJ_REPR_B (1)
 
 // A MicroPython object is a machine word having the following form (called R):
 //  - iiiiiiii iiiiiiii iiiiiiii iiiiiii1 small int with 31-bit signed value
-//  - 01111111 1qqqqqqq qqqqqqqq qqqqq110 str with 20-bit qstr value
+//  - 01111111 1qqqqqqq qqqqqqqq qqqq0110 str with 19-bit qstr value
+//  - 01111111 10000000 00000000 ssss1110 immediate object with 4-bit value
 //  - s1111111 10000000 00000000 00000010 +/- inf
 //  - s1111111 1xxxxxxx xxxxxxxx xxxxx010 nan, x != 0
 //  - seeeeeee efffffff ffffffff ffffff10 30-bit fp, e != 0xff
 //  - pppppppp pppppppp pppppppp pppppp00 ptr (4 byte alignment)
-// Str and float stored as O = R + 0x80800000, retrieved as R = O - 0x80800000.
-// This makes strs easier to encode/decode as they have zeros in the top 9 bits.
+// Str, immediate and float stored as O = R + 0x80800000, retrieved as R = O - 0x80800000.
+// This makes strs/immediates easier to encode/decode as they have zeros in the top 9 bits.
 // This scheme only works with 32-bit word size and float enabled.
 #define MICROPY_OBJ_REPR_C (2)
 
@@ -98,6 +101,7 @@
 //  - 01111111 11111000 00000000 00000000 00000000 00000000 00000000 00000000 normalised nan
 //  - 01111111 11111101 iiiiiiii iiiiiiii iiiiiiii iiiiiiii iiiiiiii iiiiiii1 small int
 //  - 01111111 11111110 00000000 00000000 qqqqqqqq qqqqqqqq qqqqqqqq qqqqqqq1 str
+//  - 01111111 11111111 ss000000 00000000 00000000 00000000 00000000 00000000 immediate object
 //  - 01111111 11111100 00000000 00000000 pppppppp pppppppp pppppppp pppppp00 ptr (4 byte alignment)
 // Stored as O = R + 0x8004000000000000, retrieved as R = O - 0x8004000000000000.
 // This makes pointers have all zeros in the top 32 bits.

py/obj.h

@@ -87,9 +87,14 @@ static inline bool mp_obj_is_small_int(mp_const_obj_t o)
 #define MP_OBJ_NEW_SMALL_INT(small_int) ((mp_obj_t)((((mp_uint_t)(small_int)) << 1) | 1))
 
 static inline bool mp_obj_is_qstr(mp_const_obj_t o)
-    { return ((((mp_int_t)(o)) & 3) == 2); }
-#define MP_OBJ_QSTR_VALUE(o) (((mp_uint_t)(o)) >> 2)
-#define MP_OBJ_NEW_QSTR(qst) ((mp_obj_t)((((mp_uint_t)(qst)) << 2) | 2))
+    { return ((((mp_int_t)(o)) & 7) == 2); }
+#define MP_OBJ_QSTR_VALUE(o) (((mp_uint_t)(o)) >> 3)
+#define MP_OBJ_NEW_QSTR(qst) ((mp_obj_t)((((mp_uint_t)(qst)) << 3) | 2))
+
+static inline bool mp_obj_is_immediate_obj(mp_const_obj_t o)
+    { return ((((mp_int_t)(o)) & 7) == 6); }
+#define MP_OBJ_IMMEDIATE_OBJ_VALUE(o) (((mp_uint_t)(o)) >> 3)
+#define MP_OBJ_NEW_IMMEDIATE_OBJ(val) ((mp_obj_t)(((val) << 3) | 6))
 
 #if MICROPY_PY_BUILTINS_FLOAT
 #define mp_const_float_e MP_ROM_PTR(&mp_const_float_e_obj)
@@ -113,9 +118,14 @@ static inline bool mp_obj_is_small_int(mp_const_obj_t o)
 #define MP_OBJ_NEW_SMALL_INT(small_int) ((mp_obj_t)((((mp_uint_t)(small_int)) << 2) | 1))
 
 static inline bool mp_obj_is_qstr(mp_const_obj_t o)
-    { return ((((mp_int_t)(o)) & 3) == 3); }
-#define MP_OBJ_QSTR_VALUE(o) (((mp_uint_t)(o)) >> 2)
-#define MP_OBJ_NEW_QSTR(qst) ((mp_obj_t)((((mp_uint_t)(qst)) << 2) | 3))
+    { return ((((mp_int_t)(o)) & 7) == 3); }
+#define MP_OBJ_QSTR_VALUE(o) (((mp_uint_t)(o)) >> 3)
+#define MP_OBJ_NEW_QSTR(qst) ((mp_obj_t)((((mp_uint_t)(qst)) << 3) | 3))
+
+static inline bool mp_obj_is_immediate_obj(mp_const_obj_t o)
+    { return ((((mp_int_t)(o)) & 7) == 7); }
+#define MP_OBJ_IMMEDIATE_OBJ_VALUE(o) (((mp_uint_t)(o)) >> 3)
+#define MP_OBJ_NEW_IMMEDIATE_OBJ(val) ((mp_obj_t)(((val) << 3) | 7))
 
 #if MICROPY_PY_BUILTINS_FLOAT
 #define mp_const_float_e MP_ROM_PTR(&mp_const_float_e_obj)
@@ -161,9 +171,14 @@ static inline mp_obj_t mp_obj_new_float(mp_float_t f) {
 #endif
 
 static inline bool mp_obj_is_qstr(mp_const_obj_t o)
-    { return (((mp_uint_t)(o)) & 0xff800007) == 0x00000006; }
-#define MP_OBJ_QSTR_VALUE(o) (((mp_uint_t)(o)) >> 3)
-#define MP_OBJ_NEW_QSTR(qst) ((mp_obj_t)((((mp_uint_t)(qst)) << 3) | 0x00000006))
+    { return (((mp_uint_t)(o)) & 0xff80000f) == 0x00000006; }
+#define MP_OBJ_QSTR_VALUE(o) (((mp_uint_t)(o)) >> 4)
+#define MP_OBJ_NEW_QSTR(qst) ((mp_obj_t)((((mp_uint_t)(qst)) << 4) | 0x00000006))
+
+static inline bool mp_obj_is_immediate_obj(mp_const_obj_t o)
+    { return (((mp_uint_t)(o)) & 0xff80000f) == 0x0000000e; }
+#define MP_OBJ_IMMEDIATE_OBJ_VALUE(o) (((mp_uint_t)(o)) >> 4)
+#define MP_OBJ_NEW_IMMEDIATE_OBJ(val) ((mp_obj_t)(((val) << 4) | 0xe))
 
 static inline bool mp_obj_is_obj(mp_const_obj_t o)
     { return ((((mp_int_t)(o)) & 3) == 0); }
@@ -180,6 +195,11 @@ static inline bool mp_obj_is_qstr(mp_const_obj_t o)
 #define MP_OBJ_QSTR_VALUE(o) ((((uint32_t)(o)) >> 1) & 0xffffffff)
 #define MP_OBJ_NEW_QSTR(qst) ((mp_obj_t)(((uint64_t)(((uint32_t)(qst)) << 1)) | 0x0002000000000001))
 
+static inline bool mp_obj_is_immediate_obj(mp_const_obj_t o)
+    { return ((((uint64_t)(o)) & 0xffff000000000000) == 0x0003000000000000); }
+#define MP_OBJ_IMMEDIATE_OBJ_VALUE(o) ((((uint32_t)(o)) >> 46) & 3)
+#define MP_OBJ_NEW_IMMEDIATE_OBJ(val) (((uint64_t)(val) << 46) | 0x0003000000000000)
+
 #if MICROPY_PY_BUILTINS_FLOAT
 
 #if MICROPY_FLOAT_IMPL != MICROPY_FLOAT_IMPL_DOUBLE