An optimizer bug with emscripten's WebAssembly backend

asmjs.html

<script src="asmjs.js"></script>

FGNode.cpp

#include "FGNode.h"
#include <stdio.h>

bool Node::supportsFillPaintData() const {
  return usesGeometryCache(_fields._type);
}

const PaintData& Node::fillPaintData() const {
  const auto* value = _fields._fillPaintData.get();
  if (!supportsFillPaintData() || !value) {
    static PaintData emptyPaintData;
    return emptyPaintData;
  }
  return *value;
}

bool Node::hasPaintedFill() const {
  if (_fields._type == NodeType::B) return false;
  if (!fillPaintData().containsEnabledVisiblePaint()) return false;
  return true;
}

int main() {
  SceneGraph scene;
  auto rect = scene.findOrCreateNode(1, 0);
  rect->_fields._type = NodeType::C;
  rect->_fields._fillPaintData.reset(new PaintData);
  rect->_fields._fillPaintData->paints.emplace_back(new Paint);
  bool value = rect->hasPaintedFill();
  printf("hasPaintedFill is %d\n", value);
  return 0;
}

Node* SceneGraph::findOrCreateNode(int guid, int sessionID) {
  std::unique_ptr<Node> owned(new Node(this, guid));
  auto node = owned.get();
  _nodes.emplace_back(std::move(owned));
  return node;
}

FGNode.h

#pragma once

#include "FGPaint.h"

struct SceneGraph;

enum class NodeType : uint8_t {
  A,
  B,
  C,
  D,
};

inline bool usesGeometryCache(NodeType type) {
  return type >= NodeType::B && type <= NodeType::D;
}

struct DenseFieldToAny {
  NodeType _type = {};
  std::unique_ptr<PaintData> _fillPaintData;
};

struct Node {
  Node(SceneGraph* scene_, int uniqueID) : scene(scene_), _uniqueID(uniqueID) {}

  const PaintData& fillPaintData() const;
  bool hasPaintedFill() const;
  bool supportsFillPaintData() const;

  SceneGraph* const scene;
  int _uniqueID = 0;
  DenseFieldToAny _fields;
};

struct SceneGraph {
  Node* findOrCreateNode(int guid, int sessionID);

  std::vector<std::unique_ptr<Node>> _nodes;
};

FGPaint.cpp

#include "FGPaint.h"

bool PaintData::containsEnabledVisiblePaint() const {
  for (const auto &paint : paints) {
    if (paint->isVisible()) {
      return true;
    }
  }

  return false;
}

FGPaint.h

#pragma once

#include <vector>
#include <memory>

struct Paint {
  bool isVisible() const { return _enabled && _opacity > 0; }

private:
  bool _enabled = true;
  float _opacity = 1.0f;
};

struct PaintData {
  bool containsEnabledVisiblePaint() const;

  std::vector<std::unique_ptr<Paint>> paints;
};

Makefile

build:
	c++ *.cpp -std=c++11 -O3
	./a.out
	emcc *.cpp -std=c++11 -O3 -o asmjs.js
	emcc *.cpp -std=c++11 -O3 -s WASM=1 -o wasm.js

wasm.html

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