diff options
Diffstat (limited to 'py/vm.c')
| -rw-r--r-- | py/vm.c | 32 |
1 files changed, 29 insertions, 3 deletions
@@ -195,6 +195,22 @@ #define TRACE_TICK(current_ip, current_sp, is_exception) #endif // MICROPY_PY_SYS_SETTRACE +#if MICROPY_PY_BUILTINS_SLICE +// This function is marked "no inline" so it doesn't increase the C stack usage of the main VM function. +MP_NOINLINE static mp_obj_t *build_slice_stack_allocated(byte op, mp_obj_t *sp, mp_obj_t step) { + mp_obj_t stop = sp[2]; + mp_obj_t start = sp[1]; + mp_obj_slice_t slice = { .base = { .type = &mp_type_slice }, .start = start, .stop = stop, .step = step }; + if (op == MP_BC_LOAD_SUBSCR) { + SET_TOP(mp_obj_subscr(TOP(), MP_OBJ_FROM_PTR(&slice), MP_OBJ_SENTINEL)); + } else { // MP_BC_STORE_SUBSCR + mp_obj_subscr(TOP(), MP_OBJ_FROM_PTR(&slice), sp[-1]); + sp -= 2; + } + return sp; +} +#endif + // fastn has items in reverse order (fastn[0] is local[0], fastn[-1] is local[1], etc) // sp points to bottom of stack which grows up // returns: @@ -849,9 +865,19 @@ unwind_jump:; // 3-argument slice includes step step = POP(); } - mp_obj_t stop = POP(); - mp_obj_t start = TOP(); - SET_TOP(mp_obj_new_slice(start, stop, step)); + if ((*ip == MP_BC_LOAD_SUBSCR || *ip == MP_BC_STORE_SUBSCR) && mp_obj_is_native_type(mp_obj_get_type(sp[-2]))) { + // Fast path optimisation for when the BUILD_SLICE is immediately followed + // by a LOAD/STORE_SUBSCR for a native 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++; + sp = build_slice_stack_allocated(op, sp - 2, step); + } else { + mp_obj_t stop = POP(); + mp_obj_t start = TOP(); + SET_TOP(mp_obj_new_slice(start, stop, step)); + } DISPATCH(); } #endif |