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Always use load_inst to load bytecode. #7

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Merged
vext01 merged 1 commit into from
Mar 17, 2026
Merged

Always use load_inst to load bytecode. #7

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96 changes: 62 additions & 34 deletions py/vm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -63,8 +63,8 @@
#define DECODE_UINT \
mp_uint_t unum = 0; \
do { \
unum = (unum << 7) + (*ip & 0x7f); \
} while ((*ip++ & 0x80) != 0)
unum = (unum << 7) + (load_inst(ip) & 0x7f); \
} while ((load_inst(ip++) & 0x80) != 0)

#define DECODE_ULABEL \
size_t ulab; \
Expand All @@ -78,6 +78,18 @@
} \
} while (0)

#define DECODE_ULABEL_LOAD_INST \
size_t ulab; \
do { \
if (load_inst(ip) & 0x80) { \
ulab = ((load_inst(ip) & 0x7f) | (load_inst(ip+1) << 7)); \
ip += 2; \
} else { \
ulab = load_inst(ip); \
ip += 1; \
} \
} while (0)

#define DECODE_SLABEL \
size_t slab; \
do { \
Expand All @@ -90,6 +102,18 @@
} \
} while (0)

#define DECODE_SLABEL_LOAD_INST \
size_t slab; \
do { \
if (load_inst(ip) & 0x80) { \
slab = ((load_inst(ip) & 0x7f) | (load_inst(ip+1) << 7)) - 0x4000; \
ip += 2; \
} else { \
slab = load_inst(ip) - 0x40; \
ip += 1; \
} \
} while (0)

#if MICROPY_EMIT_BYTECODE_USES_QSTR_TABLE

#define DECODE_QSTR \
Expand Down Expand Up @@ -216,14 +240,18 @@ MP_NOINLINE static mp_obj_t *build_slice_stack_allocated(byte op, mp_obj_t *sp,
#endif

#ifdef USE_YK
#define NOOPT_VAL(X) asm volatile("" : "+r,m"(X) : : "memory");
// Elide instruction lookup.
//
// FIXME: Can the bytecode be mutated? If so we would need to add and promote a
// bytecode version tag (see yklua for an example).
__attribute__((yk_idempotent))
byte load_inst(const byte *pc) {
NOOPT_VAL(pc);
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@vext01 vext01 Mar 16, 2026

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Is it right to NOOPT_VAL the pc? We don't do this in yklua.

There we NOOPT_VAL the function proto version -- something we have no analog of in ykmicropython.

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@ltratt ltratt Mar 16, 2026

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Without the NOOPT_VAL it seems that load_inst gets inlined? Maybe you can have a look and see if I'm going mad, but that's what I think has happened.

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@vext01 vext01 Mar 16, 2026

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Hrm. All I can say is that without NOOPT_VAL llvm is able to "somehow remove" load_inst(), but it's not obviously via inlining. It's kind of hard to see.

I'm going to merge this for now, as I think we have bigger fish to fry.

Maybe we can revisit this later.

return *pc;
}
#else
#define load_inst(x) (*(x))
#endif

// fastn has items in reverse order (fastn[0] is local[0], fastn[-1] is local[1], etc)
Expand Down Expand Up @@ -378,13 +406,13 @@ FRAME_SETUP();

ENTRY(MP_BC_LOAD_CONST_SMALL_INT): {
mp_uint_t num = 0;
if ((ip[0] & 0x40) != 0) {
if ((load_inst(ip) & 0x40) != 0) {
// Number is negative
num--;
}
do {
num = (num << 7) | (*ip & 0x7f);
} while ((*ip++ & 0x80) != 0);
num = (num << 7) | (load_inst(ip) & 0x7f);
} while ((load_inst(ip++) & 0x80) != 0);
PUSH(MP_OBJ_NEW_SMALL_INT(num));
DISPATCH();
}
Expand Down Expand Up @@ -602,29 +630,29 @@ FRAME_SETUP();
}

ENTRY(MP_BC_JUMP): {
DECODE_SLABEL;
DECODE_SLABEL_LOAD_INST;
ip += slab;
DISPATCH_WITH_PEND_EXC_CHECK();
}

ENTRY(MP_BC_POP_JUMP_IF_TRUE): {
DECODE_SLABEL;
DECODE_SLABEL_LOAD_INST;
if (mp_obj_is_true(POP())) {
ip += slab;
}
DISPATCH_WITH_PEND_EXC_CHECK();
}

ENTRY(MP_BC_POP_JUMP_IF_FALSE): {
DECODE_SLABEL;
DECODE_SLABEL_LOAD_INST;
if (!mp_obj_is_true(POP())) {
ip += slab;
}
DISPATCH_WITH_PEND_EXC_CHECK();
}

ENTRY(MP_BC_JUMP_IF_TRUE_OR_POP): {
DECODE_ULABEL;
DECODE_ULABEL_LOAD_INST;
if (mp_obj_is_true(TOP())) {
ip += ulab;
} else {
Expand All @@ -634,7 +662,7 @@ FRAME_SETUP();
}

ENTRY(MP_BC_JUMP_IF_FALSE_OR_POP): {
DECODE_ULABEL;
DECODE_ULABEL_LOAD_INST;
if (mp_obj_is_true(TOP())) {
sp--;
} else {
Expand Down Expand Up @@ -712,9 +740,9 @@ FRAME_SETUP();

ENTRY(MP_BC_UNWIND_JUMP): {
MARK_EXC_IP_SELECTIVE();
DECODE_SLABEL;
DECODE_SLABEL_LOAD_INST;
PUSH((mp_obj_t)(mp_uint_t)(uintptr_t)(ip + slab)); // push destination ip for jump
PUSH((mp_obj_t)(mp_uint_t)(*ip)); // push number of exception handlers to unwind (0x80 bit set if we also need to pop stack)
PUSH((mp_obj_t)(mp_uint_t)(load_inst(ip))); // push number of exception handlers to unwind (0x80 bit set if we also need to pop stack)
unwind_jump:;
mp_uint_t unum = (mp_uint_t)POP(); // get number of exception handlers to unwind
while ((unum & 0x7f) > 0) {
Expand Down Expand Up @@ -818,7 +846,7 @@ unwind_jump:;
ENTRY(MP_BC_FOR_ITER): {
FRAME_UPDATE();
MARK_EXC_IP_SELECTIVE();
DECODE_ULABEL; // the jump offset if iteration finishes; for labels are always forward
DECODE_ULABEL_LOAD_INST; // the jump offset if iteration finishes; for labels are always forward
code_state->sp = sp;
mp_obj_t obj;
if (*(sp - MP_OBJ_ITER_BUF_NSLOTS + 1) == MP_OBJ_NULL) {
Expand All @@ -845,7 +873,7 @@ unwind_jump:;
ENTRY(MP_BC_POP_EXCEPT_JUMP): {
assert(exc_sp >= exc_stack);
POP_EXC_BLOCK();
DECODE_ULABEL;
DECODE_ULABEL_LOAD_INST;
ip += ulab;
DISPATCH_WITH_PEND_EXC_CHECK();
}
Expand Down Expand Up @@ -893,18 +921,18 @@ unwind_jump:;
ENTRY(MP_BC_BUILD_SLICE): {
MARK_EXC_IP_SELECTIVE();
mp_obj_t step = mp_const_none;
if (*ip++ == 3) {
if (load_inst(ip++) == 3) {
// 3-argument slice includes step
step = POP();
}
if ((*ip == MP_BC_LOAD_SUBSCR || *ip == MP_BC_STORE_SUBSCR)
if ((load_inst(ip) == MP_BC_LOAD_SUBSCR || load_inst(ip) == MP_BC_STORE_SUBSCR)
&& (mp_obj_get_type(sp[-2])->flags & MP_TYPE_FLAG_SUBSCR_ALLOWS_STACK_SLICE)) {
// Fast path optimisation for when the BUILD_SLICE is immediately followed
// by a LOAD/STORE_SUBSCR for an accepting type, to avoid needing to allocate
// the slice on the heap. In some cases (e.g. a[1:3] = x) this can result
// in no allocations at all. We can't do this for instance types because
// the get/set/delattr implementation may keep a reference to the slice.
byte op = *ip++;
byte op = load_inst(ip++);
sp = build_slice_stack_allocated(op, sp - 2, step);
} else {
mp_obj_t stop = POP();
Expand Down Expand Up @@ -966,7 +994,7 @@ unwind_jump:;

ENTRY(MP_BC_MAKE_CLOSURE): {
DECODE_PTR;
size_t n_closed_over = *ip++;
size_t n_closed_over = load_inst(ip++);
// Stack layout: closed_overs <- TOS
sp -= n_closed_over - 1;
SET_TOP(mp_make_closure_from_proto_fun(ptr, code_state->fun_bc->context, n_closed_over, sp));
Expand All @@ -975,7 +1003,7 @@ unwind_jump:;

ENTRY(MP_BC_MAKE_CLOSURE_DEFARGS): {
DECODE_PTR;
size_t n_closed_over = *ip++;
size_t n_closed_over = load_inst(ip++);
// Stack layout: def_tuple def_dict closed_overs <- TOS
sp -= 2 + n_closed_over - 1;
SET_TOP(mp_make_closure_from_proto_fun(ptr, code_state->fun_bc->context, 0x100 | n_closed_over, sp));
Expand Down Expand Up @@ -1311,50 +1339,50 @@ unwind_jump:;

#if MICROPY_OPT_COMPUTED_GOTO
ENTRY(MP_BC_LOAD_CONST_SMALL_INT_MULTI):
PUSH(MP_OBJ_NEW_SMALL_INT((mp_int_t)ip[-1] - MP_BC_LOAD_CONST_SMALL_INT_MULTI - MP_BC_LOAD_CONST_SMALL_INT_MULTI_EXCESS));
PUSH(MP_OBJ_NEW_SMALL_INT((mp_int_t)load_inst(ip-1) - MP_BC_LOAD_CONST_SMALL_INT_MULTI - MP_BC_LOAD_CONST_SMALL_INT_MULTI_EXCESS));
DISPATCH();

ENTRY(MP_BC_LOAD_FAST_MULTI):
obj_shared = fastn[MP_BC_LOAD_FAST_MULTI - (mp_int_t)ip[-1]];
obj_shared = fastn[MP_BC_LOAD_FAST_MULTI - (mp_int_t)load_inst(ip-1)];
goto load_check;

ENTRY(MP_BC_STORE_FAST_MULTI):
fastn[MP_BC_STORE_FAST_MULTI - (mp_int_t)ip[-1]] = POP();
fastn[MP_BC_STORE_FAST_MULTI - (mp_int_t)load_inst(ip-1)] = POP();
DISPATCH();

ENTRY(MP_BC_UNARY_OP_MULTI):
MARK_EXC_IP_SELECTIVE();
SET_TOP(mp_unary_op(ip[-1] - MP_BC_UNARY_OP_MULTI, TOP()));
SET_TOP(mp_unary_op(load_inst(ip-1) - MP_BC_UNARY_OP_MULTI, TOP()));
DISPATCH();

ENTRY(MP_BC_BINARY_OP_MULTI): {
MARK_EXC_IP_SELECTIVE();
mp_obj_t rhs = POP();
mp_obj_t lhs = TOP();
SET_TOP(mp_binary_op(ip[-1] - MP_BC_BINARY_OP_MULTI, lhs, rhs));
SET_TOP(mp_binary_op(load_inst(ip-1) - MP_BC_BINARY_OP_MULTI, lhs, rhs));
DISPATCH();
}

ENTRY_DEFAULT:
MARK_EXC_IP_SELECTIVE();
#else
ENTRY_DEFAULT:
if (ip[-1] < MP_BC_LOAD_CONST_SMALL_INT_MULTI + MP_BC_LOAD_CONST_SMALL_INT_MULTI_NUM) {
PUSH(MP_OBJ_NEW_SMALL_INT((mp_int_t)ip[-1] - MP_BC_LOAD_CONST_SMALL_INT_MULTI - MP_BC_LOAD_CONST_SMALL_INT_MULTI_EXCESS));
if (load_inst(ip-1) < MP_BC_LOAD_CONST_SMALL_INT_MULTI + MP_BC_LOAD_CONST_SMALL_INT_MULTI_NUM) {
PUSH(MP_OBJ_NEW_SMALL_INT((mp_int_t)load_inst(ip-1) - MP_BC_LOAD_CONST_SMALL_INT_MULTI - MP_BC_LOAD_CONST_SMALL_INT_MULTI_EXCESS));
DISPATCH();
} else if (ip[-1] < MP_BC_LOAD_FAST_MULTI + MP_BC_LOAD_FAST_MULTI_NUM) {
obj_shared = fastn[MP_BC_LOAD_FAST_MULTI - (mp_int_t)ip[-1]];
} else if (load_inst(ip-1) < MP_BC_LOAD_FAST_MULTI + MP_BC_LOAD_FAST_MULTI_NUM) {
obj_shared = fastn[MP_BC_LOAD_FAST_MULTI - (mp_int_t)load_inst(ip-1)];
goto load_check;
} else if (ip[-1] < MP_BC_STORE_FAST_MULTI + MP_BC_STORE_FAST_MULTI_NUM) {
fastn[MP_BC_STORE_FAST_MULTI - (mp_int_t)ip[-1]] = POP();
} else if (load_inst(ip-1) < MP_BC_STORE_FAST_MULTI + MP_BC_STORE_FAST_MULTI_NUM) {
fastn[MP_BC_STORE_FAST_MULTI - (mp_int_t)load_inst(ip-1)] = POP();
DISPATCH();
} else if (ip[-1] < MP_BC_UNARY_OP_MULTI + MP_BC_UNARY_OP_MULTI_NUM) {
SET_TOP(mp_unary_op(ip[-1] - MP_BC_UNARY_OP_MULTI, TOP()));
} else if (load_inst(ip-1) < MP_BC_UNARY_OP_MULTI + MP_BC_UNARY_OP_MULTI_NUM) {
SET_TOP(mp_unary_op(load_inst(ip-1) - MP_BC_UNARY_OP_MULTI, TOP()));
DISPATCH();
} else if (ip[-1] < MP_BC_BINARY_OP_MULTI + MP_BC_BINARY_OP_MULTI_NUM) {
} else if (load_inst(ip-1) < MP_BC_BINARY_OP_MULTI + MP_BC_BINARY_OP_MULTI_NUM) {
mp_obj_t rhs = POP();
mp_obj_t lhs = TOP();
SET_TOP(mp_binary_op(ip[-1] - MP_BC_BINARY_OP_MULTI, lhs, rhs));
SET_TOP(mp_binary_op(load_inst(ip-1) - MP_BC_BINARY_OP_MULTI, lhs, rhs));
DISPATCH();
} else
#endif // MICROPY_OPT_COMPUTED_GOTO
Expand Down