Optimize EvaluatorStack

PiperOrigin-RevId: 742235956

Author: jcking

eval/eval/BUILD

@@ -125,17 +125,20 @@ cc_test(
 
 cc_library(
     name = "evaluator_stack",
-    srcs = [
-        "evaluator_stack.cc",
-    ],
     hdrs = [
         "evaluator_stack.h",
     ],
     deps = [
         ":attribute_trail",
         "//common:value",
+        "//internal:align",
+        "//internal:new",
         "@com_google_absl//absl/base:core_headers",
-        "@com_google_absl//absl/log:absl_log",
+        "@com_google_absl//absl/base:dynamic_annotations",
+        "@com_google_absl//absl/base:nullability",
+        "@com_google_absl//absl/log:absl_check",
+        "@com_google_absl//absl/meta:type_traits",
+        "@com_google_absl//absl/types:optional",
         "@com_google_absl//absl/types:span",
     ],
 )

eval/eval/attribute_trail.h

@@ -29,11 +29,19 @@ class AttributeTrail {
   explicit AttributeTrail(cel::Attribute attribute)
       : attribute_(std::move(attribute)) {}
 
+  // NOLINTNEXTLINE(google-explicit-constructor)
+  AttributeTrail(absl::nullopt_t) : AttributeTrail() {}
+
   AttributeTrail(const AttributeTrail&) = default;
   AttributeTrail& operator=(const AttributeTrail&) = default;
   AttributeTrail(AttributeTrail&&) = default;
   AttributeTrail& operator=(AttributeTrail&&) = default;
 
+  AttributeTrail& operator=(absl::nullopt_t) {
+    attribute_.reset();
+    return *this;
+  }
+
   // Creates AttributeTrail with attribute path incremented by "qualifier".
   AttributeTrail Step(cel::AttributeQualifier qualifier) const;
 

eval/eval/comprehension_step.cc

@@ -603,7 +603,7 @@ absl::Status ComprehensionNextStep::Evaluate1(ExecutionFrame* frame) const {
   if (!iter_range->Is<cel::ListValue>()) {
     if (iter_range->Is<cel::ErrorValue>() ||
         iter_range->Is<cel::UnknownValue>()) {
-      frame->value_stack().PopAndPush(kStackSize, std::move(iter_range));
+      frame->value_stack().SwapAndPop(/*n=*/kStackSize, /*i=*/POS_ITER_RANGE);
     } else {
       frame->value_stack().PopAndPush(
           kStackSize,
@@ -689,7 +689,7 @@ absl::Status ComprehensionNextStep::Evaluate2(ExecutionFrame* frame) const {
       ABSL_FALLTHROUGH_INTENDED;
     case ValueKind::kUnknown:
       // Leave it on the stack.
-      frame->value_stack().PopAndPush(kStackSize, std::move(iter2_range));
+      frame->value_stack().SwapAndPop(/*n=*/kStackSize, /*i=*/POS_ITER2_RANGE);
       return frame->JumpTo(error_jump_offset_);
     default:
       frame->value_stack().PopAndPush(
@@ -706,7 +706,7 @@ absl::Status ComprehensionNextStep::Evaluate2(ExecutionFrame* frame) const {
     case ValueKind::kError:
       ABSL_FALLTHROUGH_INTENDED;
     case ValueKind::kUnknown:
-      frame->value_stack().PopAndPush(kStackSize, std::move(iter_range));
+      frame->value_stack().SwapAndPop(/*n=*/kStackSize, /*i=*/POS_ITER_RANGE);
       return frame->JumpTo(error_jump_offset_);
     default:
       frame->value_stack().PopAndPush(
@@ -834,7 +834,7 @@ absl::Status ComprehensionCondStep::Evaluate1(ExecutionFrame* frame) const {
   if (!loop_condition_value->Is<cel::BoolValue>()) {
     if (loop_condition_value->Is<cel::ErrorValue>() ||
         loop_condition_value->Is<cel::UnknownValue>()) {
-      frame->value_stack().PopAndPush(3, std::move(loop_condition_value));
+      frame->value_stack().SwapAndPop(/*n=*/3, /*i=*/2);
     } else {
       frame->value_stack().PopAndPush(
           3,
@@ -872,7 +872,7 @@ absl::Status ComprehensionCondStep::Evaluate2(ExecutionFrame* frame) const {
   if (!loop_condition_value->Is<cel::BoolValue>()) {
     if (loop_condition_value->Is<cel::ErrorValue>() ||
         loop_condition_value->Is<cel::UnknownValue>()) {
-      frame->value_stack().PopAndPush(4, std::move(loop_condition_value));
+      frame->value_stack().SwapAndPop(/*n=*/4, /*i=*/3);
     } else {
       frame->value_stack().PopAndPush(
           4,