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Bytecode int varlen encoding: support arbitrary values for signed ints too.

This commit is contained in:
Paul Sokolovsky 2014-02-19 15:47:59 +02:00
parent 0f96ec8268
commit 047cd40313
3 changed files with 46 additions and 16 deletions
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32
py/emitbc.c
View File

@ -123,15 +123,31 @@ STATIC void emit_write_byte_code_uint(emit_t* emit, uint num) {
*c = *p; *c = *p;
} }
// integers (for small ints) are stored as 24 bits, in excess // Similar to emit_write_byte_code_uint(), just some extra handling to encode sign
STATIC void emit_write_byte_code_byte_int(emit_t* emit, byte b1, machine_int_t num) { STATIC void emit_write_byte_code_byte_int(emit_t* emit, byte b1, machine_int_t num) {
num += 0x800000; emit_write_byte_code_byte(emit, b1);
assert(0 <= num && num <= 0xffffff);
byte* c = emit_get_cur_to_write_byte_code(emit, 4); // We store each 7 bits in a separate byte, and that's how many bytes needed
c[0] = b1; byte buf[(BYTES_PER_WORD * 8 + 7) / 7];
c[1] = num; byte *p = buf + sizeof(buf);
c[2] = num >> 8; // We encode in little-ending order, but store in big-endian, to help decoding
c[3] = num >> 16; do {
*--p = num & 0x7f;
num >>= 7;
} while (num != 0 && num != -1);
// Make sure that highest bit we stored (mask 0x40) matches sign
// of the number. If not, store extra byte just to encode sign
if (num == -1 && (*p & 0x40) == 0) {
*--p = 0x7f;
} else if (num == 0 && (*p & 0x40) != 0) {
*--p = 0;
}
byte* c = emit_get_cur_to_write_byte_code(emit, buf + sizeof(buf) - p);
while (p != buf + sizeof(buf) - 1) {
*c++ = *p++ | 0x80;
}
*c = *p;
} }
STATIC void emit_write_byte_code_byte_uint(emit_t* emit, byte b, uint num) { STATIC void emit_write_byte_code_byte_uint(emit_t* emit, byte b, uint num) {

15
py/showbc.c
View File

@ -57,11 +57,18 @@ void mp_byte_code_print(const byte *ip, int len) {
printf("LOAD_CONST_ELLIPSIS"); printf("LOAD_CONST_ELLIPSIS");
break; break;
case MP_BC_LOAD_CONST_SMALL_INT: case MP_BC_LOAD_CONST_SMALL_INT: {
unum = (ip[0] | (ip[1] << 8) | (ip[2] << 16)) - 0x800000; int num = 0;
ip += 3; if ((ip[0] & 0x40) != 0) {
printf("LOAD_CONST_SMALL_INT %d", (int)unum); // Number is negative
num--;
}
do {
num = (num << 7) | (*ip & 0x7f);
} while ((*ip++ & 0x80) != 0);
printf("LOAD_CONST_SMALL_INT %d", num);
break; break;
}
case MP_BC_LOAD_CONST_INT: case MP_BC_LOAD_CONST_INT:
DECODE_QSTR; DECODE_QSTR;

15
py/vm.c
View File

@ -156,11 +156,18 @@ dispatch_loop:
PUSH(mp_const_ellipsis); PUSH(mp_const_ellipsis);
break; break;
case MP_BC_LOAD_CONST_SMALL_INT: case MP_BC_LOAD_CONST_SMALL_INT: {
unum = (ip[0] | (ip[1] << 8) | (ip[2] << 16)) - 0x800000; int num = 0;
ip += 3; if ((ip[0] & 0x40) != 0) {
PUSH(MP_OBJ_NEW_SMALL_INT(unum)); // Number is negative
num--;
}
do {
num = (num << 7) | (*ip & 0x7f);
} while ((*ip++ & 0x80) != 0);
PUSH(MP_OBJ_NEW_SMALL_INT(num));
break; break;
}
case MP_BC_LOAD_CONST_INT: case MP_BC_LOAD_CONST_INT:
DECODE_QSTR; DECODE_QSTR;