From 395b071ae9b09f0b4fe3ce0f3a43f16ba74f01a5 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Mon, 28 Jun 2021 14:25:40 -0700
Subject: Refactor LinearExecutionWalker to a separate file. NFC (#3956)

---
 src/ir/linear-execution.h | 139 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 139 insertions(+)
 create mode 100644 src/ir/linear-execution.h

(limited to 'src/ir/linear-execution.h')

diff --git a/src/ir/linear-execution.h b/src/ir/linear-execution.h
new file mode 100644
index 000000000..b1d0b96c3
--- /dev/null
+++ b/src/ir/linear-execution.h
@@ -0,0 +1,139 @@
+/*
+ * Copyright 2021 WebAssembly Community Group participants
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef wasm_ir_linear_execution_h
+#define wasm_ir_linear_execution_h
+
+#include <wasm-traversal.h>
+#include <wasm.h>
+
+namespace wasm {
+
+// Traversal in the order of execution. This is quick and simple, but
+// does not provide the same comprehensive information that a full
+// conversion to basic blocks would. What it does give is a quick
+// way to view straightline execution traces, i.e., that have no
+// branching. This can let optimizations get most of what they
+// want without the cost of creating another AST.
+//
+// When execution is no longer linear, this notifies via a call
+// to noteNonLinear().
+
+template<typename SubType, typename VisitorType = Visitor<SubType>>
+struct LinearExecutionWalker : public PostWalker<SubType, VisitorType> {
+  LinearExecutionWalker() = default;
+
+  // subclasses should implement this
+  void noteNonLinear(Expression* curr) { abort(); }
+
+  static void doNoteNonLinear(SubType* self, Expression** currp) {
+    self->noteNonLinear(*currp);
+  }
+
+  static void scan(SubType* self, Expression** currp) {
+    Expression* curr = *currp;
+
+    switch (curr->_id) {
+      case Expression::Id::InvalidId:
+        abort();
+      case Expression::Id::BlockId: {
+        self->pushTask(SubType::doVisitBlock, currp);
+        if (curr->cast<Block>()->name.is()) {
+          self->pushTask(SubType::doNoteNonLinear, currp);
+        }
+        auto& list = curr->cast<Block>()->list;
+        for (int i = int(list.size()) - 1; i >= 0; i--) {
+          self->pushTask(SubType::scan, &list[i]);
+        }
+        break;
+      }
+      case Expression::Id::IfId: {
+        self->pushTask(SubType::doVisitIf, currp);
+        self->pushTask(SubType::doNoteNonLinear, currp);
+        self->maybePushTask(SubType::scan, &curr->cast<If>()->ifFalse);
+        self->pushTask(SubType::doNoteNonLinear, currp);
+        self->pushTask(SubType::scan, &curr->cast<If>()->ifTrue);
+        self->pushTask(SubType::doNoteNonLinear, currp);
+        self->pushTask(SubType::scan, &curr->cast<If>()->condition);
+        break;
+      }
+      case Expression::Id::LoopId: {
+        self->pushTask(SubType::doVisitLoop, currp);
+        self->pushTask(SubType::scan, &curr->cast<Loop>()->body);
+        self->pushTask(SubType::doNoteNonLinear, currp);
+        break;
+      }
+      case Expression::Id::BreakId: {
+        self->pushTask(SubType::doVisitBreak, currp);
+        self->pushTask(SubType::doNoteNonLinear, currp);
+        self->maybePushTask(SubType::scan, &curr->cast<Break>()->condition);
+        self->maybePushTask(SubType::scan, &curr->cast<Break>()->value);
+        break;
+      }
+      case Expression::Id::SwitchId: {
+        self->pushTask(SubType::doVisitSwitch, currp);
+        self->pushTask(SubType::doNoteNonLinear, currp);
+        self->maybePushTask(SubType::scan, &curr->cast<Switch>()->value);
+        self->pushTask(SubType::scan, &curr->cast<Switch>()->condition);
+        break;
+      }
+      case Expression::Id::ReturnId: {
+        self->pushTask(SubType::doVisitReturn, currp);
+        self->pushTask(SubType::doNoteNonLinear, currp);
+        self->maybePushTask(SubType::scan, &curr->cast<Return>()->value);
+        break;
+      }
+      case Expression::Id::TryId: {
+        self->pushTask(SubType::doVisitTry, currp);
+        self->pushTask(SubType::doNoteNonLinear, currp);
+        auto& list = curr->cast<Try>()->catchBodies;
+        for (int i = int(list.size()) - 1; i >= 0; i--) {
+          self->pushTask(SubType::scan, &list[i]);
+          self->pushTask(SubType::doNoteNonLinear, currp);
+        }
+        self->pushTask(SubType::scan, &curr->cast<Try>()->body);
+        break;
+      }
+      case Expression::Id::ThrowId: {
+        self->pushTask(SubType::doVisitThrow, currp);
+        self->pushTask(SubType::doNoteNonLinear, currp);
+        auto& list = curr->cast<Throw>()->operands;
+        for (int i = int(list.size()) - 1; i >= 0; i--) {
+          self->pushTask(SubType::scan, &list[i]);
+        }
+        break;
+      }
+      case Expression::Id::RethrowId: {
+        self->pushTask(SubType::doVisitRethrow, currp);
+        self->pushTask(SubType::doNoteNonLinear, currp);
+        break;
+      }
+      case Expression::Id::UnreachableId: {
+        self->pushTask(SubType::doVisitUnreachable, currp);
+        self->pushTask(SubType::doNoteNonLinear, currp);
+        break;
+      }
+      default: {
+        // other node types do not have control flow, use regular post-order
+        PostWalker<SubType, VisitorType>::scan(self, currp);
+      }
+    }
+  }
+};
+
+} // namespace wasm
+
+#endif // wasm_ir_linear_execution_h
-- 
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