Subtype: Code clean for union state stack. (JuliaLang#48479)

src/subtype.c

@@ -519,23 +519,38 @@ static jl_unionall_t *rename_unionall(jl_unionall_t *u)
 
 static int subtype(jl_value_t *x, jl_value_t *y, jl_stenv_t *e, int param);
 
-static jl_value_t *pick_union_element(jl_value_t *u JL_PROPAGATES_ROOT, jl_stenv_t *e, int8_t R) JL_NOTSAFEPOINT
+static int next_union_state(jl_stenv_t *e, int8_t R) JL_NOTSAFEPOINT
 {
  jl_unionstate_t *state = R ? &e->Runions : &e->Lunions;
+ if (state->more == 0)
+ return 0;
+ // reset `used` and let `pick_union_decision` clean the stack.
+ state->used = state->more;
+ statestack_set(state, state->used - 1, 1);
+ return 1;
+}
+
+static int pick_union_decision(jl_stenv_t *e, int8_t R) JL_NOTSAFEPOINT
+{
+ jl_unionstate_t *state = R ? &e->Runions : &e->Lunions;
+ if (state->depth >= state->used) {
+ statestack_set(state, state->used, 0);
+ state->used++;
+ }
+ int ui = statestack_get(state, state->depth);
+ state->depth++;
+ if (ui == 0)
+ state->more = state->depth; // memorize that this was the deepest available choice
+ return ui;
+}
+
+static jl_value_t *pick_union_element(jl_value_t *u JL_PROPAGATES_ROOT, jl_stenv_t *e, int8_t R) JL_NOTSAFEPOINT
+{
  do {
- if (state->depth >= state->used) {
- statestack_set(state, state->used, 0);
- state->used++;
- }
- int ui = statestack_get(state, state->depth);
- state->depth++;
- if (ui == 0) {
- state->more = state->depth; // memorize that this was the deepest available choice
- u = ((jl_uniontype_t*)u)->a;
- }
- else {
+ if (pick_union_decision(e, R))
  u = ((jl_uniontype_t*)u)->b;
- }
+ else
+ u = ((jl_uniontype_t*)u)->a;
  } while (jl_is_uniontype(u));
  return u;
 }
@@ -1208,15 +1223,7 @@ static int subtype(jl_value_t *x, jl_value_t *y, jl_stenv_t *e, int param)
  // of unions and vars: if matching `typevar <: union`, first try to match the whole
  // union against the variable before trying to take it apart to see if there are any
  // variables lurking inside.
- jl_unionstate_t *state = &e->Runions;
- if (state->depth >= state->used) {
- statestack_set(state, state->used, 0);
- state->used++;
- }
- ui = statestack_get(state, state->depth);
- state->depth++;
- if (ui == 0)
- state->more = state->depth; // memorize that this was the deepest available choice
+ ui = pick_union_decision(e, 1);
  }
  if (ui == 1)
  y = pick_union_element(y, e, 1);
@@ -1383,14 +1390,7 @@ static int forall_exists_equal(jl_value_t *x, jl_value_t *y, jl_stenv_t *e)
  // here to try the usual algorithm if subtyping later fails.
  jl_unionstate_t *state = &e->Runions;
  jl_saved_unionstate_t oldRunions; push_unionstate(&oldRunions, state);
- if (state->depth >= state->used) {
- statestack_set(state, state->used, 0);
- state->used++;
- }
- int ui = statestack_get(state, state->depth);
- state->depth++;
- if (ui == 0) {
- state->more = state->depth; // memorize that this was the deepest available choice
+ if (pick_union_decision(e, 1) == 0) {
  if (equal_unions((jl_uniontype_t*)x, (jl_uniontype_t*)y, e))
  return 1;
  pop_unionstate(state, &oldRunions);
@@ -1414,18 +1414,12 @@ static int forall_exists_equal(jl_value_t *x, jl_value_t *y, jl_stenv_t *e)
  pop_unionstate(&e->Runions, &oldRunions);
  }
  else {
- int lastset = 0;
  while (1) {
  e->Lunions.more = 0;
  e->Lunions.depth = 0;
  sub = subtype(x, y, e, 2);
- int set = e->Lunions.more;
- if (!sub || !set)
+ if (!sub || !next_union_state(e, 0))
  break;
- for (int i = set; i <= lastset; i++)
- statestack_set(&e->Lunions, i, 0);
- lastset = set - 1;
- statestack_set(&e->Lunions, lastset, 1);
  }
  }
 
@@ -1436,16 +1430,14 @@ static int forall_exists_equal(jl_value_t *x, jl_value_t *y, jl_stenv_t *e)
 static int exists_subtype(jl_value_t *x, jl_value_t *y, jl_stenv_t *e, jl_value_t *saved, jl_savedenv_t *se, int param)
 {
  e->Runions.used = 0;
- int lastset = 0;
  while (1) {
  e->Runions.depth = 0;
  e->Runions.more = 0;
  e->Lunions.depth = 0;
  e->Lunions.more = 0;
  if (subtype(x, y, e, param))
  return 1;
- int set = e->Runions.more;
- if (set) {
+ if (next_union_state(e, 1)) {
  // We preserve `envout` here as `subtype_unionall` needs previous assigned env values.
  int oldidx = e->envidx;
  e->envidx = e->envsz;
@@ -1456,10 +1448,6 @@ static int exists_subtype(jl_value_t *x, jl_value_t *y, jl_stenv_t *e, jl_value_
  restore_env(e, saved, se);
  return 0;
  }
- for (int i = set; i <= lastset; i++)
- statestack_set(&e->Runions, i, 0);
- lastset = set - 1;
- statestack_set(&e->Runions, lastset, 1);
  }
 }
 
@@ -1475,19 +1463,13 @@ static int forall_exists_subtype(jl_value_t *x, jl_value_t *y, jl_stenv_t *e, in
  save_env(e, &saved, &se);
 
  e->Lunions.used = 0;
- int lastset = 0;
  int sub;
  while (1) {
  sub = exists_subtype(x, y, e, saved, &se, param);
- int set = e->Lunions.more;
- if (!sub || !set)
+ if (!sub || !next_union_state(e, 0))
  break;
  free_env(&se);
  save_env(e, &saved, &se);
- for (int i = set; i <= lastset; i++)
- statestack_set(&e->Lunions, i, 0);
- lastset = set - 1;
- statestack_set(&e->Lunions, lastset, 1);
  }
 
  free_env(&se);
@@ -3326,39 +3308,30 @@ static jl_value_t *intersect_all(jl_value_t *x, jl_value_t *y, jl_stenv_t *e)
  jl_value_t **merged = &is[3];
  jl_savedenv_t se, me;
  save_env(e, saved, &se);
- int lastset = 0, niter = 0, total_iter = 0;
- jl_value_t *ii = intersect(x, y, e, 0);
- is[0] = ii; // root
+ int niter = 0, total_iter = 0;
+ is[0] = intersect(x, y, e, 0); // root
  if (is[0] != jl_bottom_type)
  niter = merge_env(e, merged, &me, niter);
  restore_env(e, *saved, &se);
- while (e->Runions.more) {
- if (e->emptiness_only && ii != jl_bottom_type)
+ while (next_union_state(e, 1)) {
+ if (e->emptiness_only && is[0] != jl_bottom_type)
  break;
  e->Runions.depth = 0;
- int set = e->Runions.more - 1;
  e->Runions.more = 0;
- statestack_set(&e->Runions, set, 1);
- for (int i = set + 1; i <= lastset; i++)
- statestack_set(&e->Runions, i, 0);
- lastset = set;
 
- is[0] = ii;
  is[1] = intersect(x, y, e, 0);
  if (is[1] != jl_bottom_type)
  niter = merge_env(e, merged, &me, niter);
  restore_env(e, *saved, &se);
  if (is[0] == jl_bottom_type)
- ii = is[1];
- else if (is[1] == jl_bottom_type)
- ii = is[0];
- else {
+ is[0] = is[1];
+ else if (is[1] != jl_bottom_type) {
  // TODO: the repeated subtype checks in here can get expensive
- ii = jl_type_union(is, 2);
+ is[0] = jl_type_union(is, 2);
  }
  total_iter++;
  if (niter > 4 || total_iter > 400000) {
- ii = y;
+ is[0] = y;
  break;
  }
  }
@@ -3368,7 +3341,7 @@ static jl_value_t *intersect_all(jl_value_t *x, jl_value_t *y, jl_stenv_t *e)
  }
  free_env(&se);
  JL_GC_POP();
- return ii;
+ return is[0];
 }
 
 // type intersection entry points