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[Explicit State Access] Decouple Next nodes in array_untuple_pass #4444

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[Explicit State Access] Decouple Next nodes in array_untuple_pass #4444

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28 changes: 21 additions & 7 deletions xls/passes/array_untuple_pass.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -134,11 +134,16 @@ absl::StatusOr<absl::flat_hash_set<Node*>> FindExternalGroups(
if (absl::c_all_of(state_read->users(), [&](Node* n) -> bool {
if (n->Is<Next>()) {
Next* nxt = n->As<Next>();
return nxt->state_read() == nxt->value() &&
nxt->state_read() == state_read;
if (nxt->has_state_read()) {
return nxt->state_read() == nxt->value() &&
nxt->state_read() == state_read;
} else {
return nxt->value() == state_read &&
nxt->state_element() == state_read->state_element();
}
}
// TODO(nelsonliang): Handle identity state elements by retrieving
// all state reads and verifying all reds are identity updates.
// all state reads and verifying all reads are identity updates.
return false;
})) {
excluded.insert(groups.Find(state_read));
Expand Down Expand Up @@ -352,10 +357,19 @@ class UntupleVisitor : public DfsVisitorWithDefault {
iter::zip(iter::count(), state_read_values, update_values)) {
XLS_RET_CHECK(state_read_node->Is<StateRead>());
StateRead* state_read = state_read_node->As<StateRead>();
XLS_RETURN_IF_ERROR(proc->MakeNodeWithName<Next>(
n->loc(), state_read, value, n->predicate(),
n->label(), IdxName(n, idx))
.status());
if (n->has_state_read()) {
XLS_RETURN_IF_ERROR(proc->MakeNodeWithName<Next>(
n->loc(), state_read, value, n->predicate(),
n->label(), IdxName(n, idx))
.status());
} else {
StateElement* state_element = state_read->state_element();
XLS_RET_CHECK(state_element != nullptr);
XLS_RETURN_IF_ERROR(proc->MakeNodeWithName<Next>(
n->loc(), state_element, value,
n->predicate(), n->label(), IdxName(n, idx))
.status());
}
}
// Remove this next from consideration.
if (n->value() != state_read) {
Expand Down
37 changes: 37 additions & 0 deletions xls/passes/array_untuple_pass_test.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -525,6 +525,32 @@ TEST_F(ArrayUntuplePassTest, ProcStateArrayWithInvoke) {
EXPECT_EQ(val2_before, val2_after);
}

TEST_F(ArrayUntuplePassTest, ProcStateArrayIdentityNextWithStateElement) {
auto p = CreatePackage();
ProcBuilder pb(TestName(), p.get());

XLS_ASSERT_OK_AND_ASSIGN(
Value init_val,
ValueBuilder::Array(
{ValueBuilder::Tuple({Value(UBits(0, 4)), Value(UBits(0, 8))}),
ValueBuilder::Tuple({Value(UBits(0, 4)), Value(UBits(0, 8))})})
.Build());

XLS_ASSERT_OK_AND_ASSIGN(StateElement * state_elem,
pb.UnreadStateElement("my_state", init_val,
/*non_synthesizable=*/false));
BValue state_read = pb.StateRead(state_elem);

// Identity next (decoupled)
pb.Next(state_elem, state_read);

XLS_ASSERT_OK_AND_ASSIGN(Proc * pr, pb.Build());
ScopedRecordIr sri(p.get());
EXPECT_THAT(RunPass(p.get()), IsOkAndHolds(false));
EXPECT_THAT(pr->StateElements(),
UnorderedElementsAre(m::StateElement("my_state")));
}

TEST_F(ArrayUntuplePassTest, ProcStateArrayNextWithStateElement) {
auto p = CreatePackage();
ProcBuilder pb(TestName(), p.get());
Expand Down Expand Up @@ -556,6 +582,17 @@ TEST_F(ArrayUntuplePassTest, ProcStateArrayNextWithStateElement) {
EXPECT_THAT(pr->StateElements(),
IsSupersetOf({m::StateElement(_, m::Type("bits[4][2]")),
m::StateElement(_, m::Type("bits[8][2]"))}));

XLS_ASSERT_OK_AND_ASSIGN(StateElement * se0, pr->GetStateElementByName(
"my_state_tuple_element_0"));
XLS_ASSERT_OK_AND_ASSIGN(StateElement * se1, pr->GetStateElementByName(
"my_state_tuple_element_1"));

// Verify next values are decoupled (no state_read operand)
EXPECT_THAT(pr->next_values(se0),
UnorderedElementsAre(m::NextWithStateElement(se0, _)));
EXPECT_THAT(pr->next_values(se1),
UnorderedElementsAre(m::NextWithStateElement(se1, _)));
}

void IrFuzzArrayUntuple(FuzzPackageWithArgs fuzz_package_with_args) {
Expand Down
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