Add a next_value node to XLS IR

Currently unimplemented in all backends, but will be used to enable dynamic state feedback in followup work.

PiperOrigin-RevId: 597977120

Author: ericastor

xls/codegen/BUILD

@@ -28,7 +28,6 @@ cc_library(
         "//xls/ir:bits",
         "//xls/ir:type",
         "@com_google_absl//absl/container:flat_hash_map",
-        "@com_google_absl//absl/strings",
     ],
 )
 
@@ -419,7 +418,6 @@ cc_library(
         "//xls/ir:op",
         "//xls/ir:register",
         "@com_google_absl//absl/container:flat_hash_map",
-        "@com_google_absl//absl/strings",
     ],
 )
 

xls/codegen/block_conversion_test.cc

@@ -127,6 +127,7 @@ class TestDelayEstimator : public DelayEstimator {
       case Op::kAfterAll:
       case Op::kMinDelay:
       case Op::kParam:
+      case Op::kNext:
       case Op::kInputPort:
       case Op::kOutputPort:
       case Op::kLiteral:

xls/codegen/block_metrics.cc

@@ -284,6 +284,7 @@ BomKindProto OpToBomKind(Op op) {
     case Op::kOutputPort:
     case Op::kMap:
     case Op::kParam:
+    case Op::kNext:
     case Op::kRegisterRead:
     case Op::kRegisterWrite:
     case Op::kInstantiationOutput:

xls/codegen/node_expressions.cc

@@ -632,6 +632,8 @@ absl::StatusOr<Expression*> NodeToExpression(
       return file->OrReduce(inputs[0], node->loc());
     case Op::kParam:
       return unimplemented();
+    case Op::kNext:
+      return unimplemented();
     case Op::kRegisterRead:
       return unimplemented();
     case Op::kRegisterWrite:

xls/codegen/side_effect_condition_pass.cc

@@ -39,9 +39,9 @@ absl::StatusOr<bool> OpShouldBeRewritten(Op op) {
   if (!OpIsSideEffecting(op)) {
     return false;
   }
-  // Channel, port, param, register, and instantiation operations are handled
-  // elsewhere. Gate ops are special and not conditional, so we ignore them
-  // here. That leaves the following ops to rewrite.
+  // Channel, port, param, state, register, and instantiation operations are
+  // handled elsewhere. Gate ops are special and not conditional, so we ignore
+  // them here. That leaves the following ops to rewrite.
   switch (op) {
     case Op::kAssert:
     case Op::kCover:
@@ -53,6 +53,7 @@ absl::StatusOr<bool> OpShouldBeRewritten(Op op) {
     case Op::kInputPort:
     case Op::kOutputPort:
     case Op::kParam:
+    case Op::kNext:
     case Op::kRegisterRead:
     case Op::kRegisterWrite:
     case Op::kInstantiationOutput:

xls/interpreter/BUILD

@@ -34,8 +34,6 @@ cc_library(
         ":block_evaluator",
         "@com_google_absl//absl/container:flat_hash_map",
         "@com_google_absl//absl/container:flat_hash_set",
-        "@com_google_absl//absl/random:bit_gen_ref",
-        "@com_google_absl//absl/random:distributions",
         "@com_google_absl//absl/status",
         "@com_google_absl//absl/status:statusor",
         "@com_google_absl//absl/strings:str_format",

xls/interpreter/ir_interpreter.cc

@@ -731,6 +731,11 @@ absl::Status IrInterpreter::HandleParam(Param* param) {
   return absl::UnimplementedError("Param not implemented in IrInterpreter");
 }
 
+absl::Status IrInterpreter::HandleNext(Next* next) {
+  return absl::UnimplementedError(
+      "Next value not implemented in IrInterpreter");
+}
+
 absl::Status IrInterpreter::HandleReverse(UnOp* reverse) {
   return SetBitsResult(reverse,
                        bits_ops::Reverse(ResolveAsBits(reverse->operand(0))));

xls/interpreter/ir_interpreter.h

@@ -113,6 +113,7 @@ class IrInterpreter : public DfsVisitor {
   absl::Status HandleOrReduce(BitwiseReductionOp* or_reduce) override;
   absl::Status HandleOutputPort(OutputPort* output_port) override;
   absl::Status HandleParam(Param* param) override;
+  absl::Status HandleNext(Next* next) override;
   absl::Status HandleReceive(Receive* receive) override;
   absl::Status HandleRegisterRead(RegisterRead* reg_read) override;
   absl::Status HandleRegisterWrite(RegisterWrite* reg_write) override;

xls/ir/BUILD

@@ -78,7 +78,6 @@ cc_library(
         ":ir",
         "//xls/common/status:ret_check",
         "//xls/common/status:status_macros",
-        "@com_google_absl//absl/memory",
         "@com_google_absl//absl/status:statusor",
         "@com_google_absl//absl/types:span",
     ],
@@ -261,7 +260,6 @@ cc_library(
         ":bits_ops",
         ":interval",
         "//xls/common/logging",
-        "@com_google_absl//absl/status:statusor",
         "@com_google_absl//absl/strings",
         "@com_google_absl//absl/strings:str_format",
         "@com_google_absl//absl/types:span",
@@ -435,7 +433,6 @@ cc_library(
     deps = [
         ":type",
         ":value",
-        "@com_google_absl//absl/strings",
         "@com_google_absl//absl/strings:str_format",
     ],
 )
@@ -579,10 +576,13 @@ cc_test(
     name = "function_builder_test",
     srcs = ["function_builder_test.cc"],
     deps = [
+        ":bits",
         ":function_builder",
         ":ir",
         ":ir_matcher",
         ":node_util",
+        ":source_location",
+        ":value",
         "//xls/common:xls_gunit",
         "//xls/common:xls_gunit_main",
         "//xls/common/status:matchers",
@@ -917,7 +917,6 @@ cc_test(
         "//xls/common:xls_gunit",
         "//xls/common:xls_gunit_main",
         "//xls/common/status:matchers",
-        "@com_google_absl//absl/strings",
     ],
 )
 
@@ -952,7 +951,6 @@ cc_library(
     hdrs = ["format_preference.h"],
     deps = [
         "@com_google_absl//absl/status:statusor",
-        "@com_google_absl//absl/strings",
         "@com_google_absl//absl/strings:str_format",
     ],
 )
@@ -1189,7 +1187,6 @@ cc_library(
     hdrs = ["big_int.h"],
     deps = [
         ":bits",
-        ":format_preference",
         "//xls/common/logging",
         "@boringssl//:crypto",
         "@com_google_absl//absl/status:statusor",
@@ -1236,7 +1233,6 @@ cc_test(
         ":number_parser",
         "//xls/common:xls_gunit",
         "//xls/common:xls_gunit_main",
-        "//xls/common/logging",
         "//xls/common/status:matchers",
         "//xls/data_structures:inline_bitmap",
         "@com_google_absl//absl/container:inlined_vector",
@@ -1369,6 +1365,7 @@ cc_library(
     hdrs = ["abstract_node_evaluator.h"],
     deps = [
         ":ir",
+        ":op",
         "//xls/common/status:status_macros",
         "@com_google_absl//absl/status",
         "@com_google_absl//absl/status:statusor",
@@ -1404,7 +1401,6 @@ cc_library(
     deps = [
         "//xls/common/logging",
         "@com_google_absl//absl/status:statusor",
-        "@com_google_absl//absl/strings",
     ],
 )
 

xls/ir/abstract_node_evaluator.h

@@ -22,6 +22,7 @@
 #include "xls/common/status/status_macros.h"
 #include "xls/ir/node.h"
 #include "xls/ir/nodes.h"
+#include "xls/ir/op.h"
 
 namespace xls {
 
@@ -177,6 +178,8 @@ absl::StatusOr<typename AbstractEvaluatorT::Vector> AbstractEvaluate(
       return default_handler(node);
     case Op::kParam:
       return default_handler(node);
+    case Op::kNext:
+      return default_handler(node);
     case Op::kRegisterRead:
       return default_handler(node);
     case Op::kRegisterWrite: