diff --git a/xls/passes/select_simplification_pass.cc b/xls/passes/select_simplification_pass.cc index fccc4f9971..d49c8b2a61 100644 --- a/xls/passes/select_simplification_pass.cc +++ b/xls/passes/select_simplification_pass.cc @@ -1114,6 +1114,15 @@ absl::StatusOr MaybeReorderSelect(Node* node, return false; } + // Side effecting operations don't have values which depend on their inputs so + // we can't replace the select with one on the selectors arguments. + // NB Only predicated state reads would get caught by this and not be caught + // by the 'unknown_operands.size() != 1' check below. Those could confuse this + // however and its better to be explicit. + if (OpIsSideEffecting(selector->op()) && selector->op() != Op::kGate) { + return false; + } + // Run through all of the selector's operands, recording the Values of any // that are known constant; this simplification applies if all but one are // known. diff --git a/xls/passes/select_simplification_pass_test.cc b/xls/passes/select_simplification_pass_test.cc index 6d4a35857c..e99ef515b1 100644 --- a/xls/passes/select_simplification_pass_test.cc +++ b/xls/passes/select_simplification_pass_test.cc @@ -70,7 +70,7 @@ class SelectSimplificationPassTest : public IrTestBase, public testing::WithParamInterface { protected: - absl::StatusOr Run(Function* f) { + absl::StatusOr Run(FunctionBase* f) { PassResults results; OptimizationContext context; if (GetParam() == AnalysisType::kTernary) { @@ -1830,6 +1830,29 @@ TEST_P(SelectSimplificationPassTest, m::Param("ugt_result"))); } +TEST_P(SelectSimplificationPassTest, PredicatedStateReadFeedSelector) { + auto p = CreatePackage(); + TokenlessProcBuilder pb(NewStyleProc{}, TestName(), "tkn", p.get()); + XLS_ASSERT_OK_AND_ASSIGN(StateElement * state_element1, + pb.UnreadStateElement("state1", Value(UBits(0, 1)))); + XLS_ASSERT_OK_AND_ASSIGN(StateElement * state_element2, + pb.UnreadStateElement("state2", Value(UBits(0, 1)))); + XLS_ASSERT_OK_AND_ASSIGN(auto in1, + pb.AddInputChannel("in1", p->GetBitsType(32))); + XLS_ASSERT_OK_AND_ASSIGN(auto in2, + pb.AddInputChannel("in2", p->GetBitsType(32))); + BValue sr1 = pb.StateRead(state_element1); + BValue sr2 = pb.StateRead(state_element2, sr1); + BValue update = pb.BitSlice( + pb.Select(sr2, {pb.ReceiveIf(in1, sr1), pb.ReceiveIf(in2, sr1)}), 0, 1); + pb.Next(state_element1, sr1); + pb.Next(state_element2, update, /*pred=*/sr1); + pb.Next(state_element2, sr1, /*pred=*/pb.Not(sr1)); + XLS_ASSERT_OK_AND_ASSIGN(Proc * proc, pb.Build()); + + EXPECT_THAT(Run(proc), IsOkAndHolds(false)); +} + INSTANTIATE_TEST_SUITE_P(SelectSimplificationPassTest, SelectSimplificationPassTest, testing::Values(AnalysisType::kTernary,