From d672fe068a068ba5ddedf73736545b9ec4bc5b2e Mon Sep 17 00:00:00 2001
From: Alexey Andreev <konsoletyper@gmail.com>
Date: Tue, 26 Jul 2016 22:06:40 +0300
Subject: [PATCH] Continue developing decompiler

---
 .../java/org/teavm/common/GraphUtils.java     |  30 +++
 .../teavm/wasm/decompile/ContextUtils.java    |  39 ----
 .../wasm/decompile/DecompileSupport.java      | 161 +++++++++++++
 .../teavm/wasm/decompile/WasmDecompiler.java  | 211 +++++++++++++-----
 4 files changed, 344 insertions(+), 97 deletions(-)
 delete mode 100644 core/src/main/java/org/teavm/wasm/decompile/ContextUtils.java
 create mode 100644 core/src/main/java/org/teavm/wasm/decompile/DecompileSupport.java

diff --git a/core/src/main/java/org/teavm/common/GraphUtils.java b/core/src/main/java/org/teavm/common/GraphUtils.java
index c9fdee2f1..d0e0862dc 100644
--- a/core/src/main/java/org/teavm/common/GraphUtils.java
+++ b/core/src/main/java/org/teavm/common/GraphUtils.java
@@ -165,6 +165,36 @@ public final class GraphUtils {
         return graph.build();
     }
 
+    public static int[] dfs(Graph graph) {
+        int[] result = new int[graph.size()];
+        int[] state = new int[graph.size()];
+        int[] stack = new int[graph.size() * 2];
+        int top = 0;
+        stack[top++] = 0;
+        int index = graph.size();
+
+        while (top > 0) {
+            int node = stack[--top];
+            switch (state[node]) {
+                case 0:
+                    state[node] = 1;
+                    stack[top++] = node;
+                    for (int successor : graph.outgoingEdges(node)) {
+                        if (state[successor] == 0) {
+                            stack[top++] = node;
+                        }
+                    }
+                    break;
+                case 1:
+                    result[node] = --index;
+                    state[node] = 2;
+                    break;
+            }
+        }
+
+        return result;
+    }
+
     public static void splitIrreducibleGraph(Graph graph, int[] weights, GraphSplittingBackend backend) {
         new IrreducibleGraphConverter().convertToReducible(graph, weights, backend);
     }
diff --git a/core/src/main/java/org/teavm/wasm/decompile/ContextUtils.java b/core/src/main/java/org/teavm/wasm/decompile/ContextUtils.java
deleted file mode 100644
index 0edf17df1..000000000
--- a/core/src/main/java/org/teavm/wasm/decompile/ContextUtils.java
+++ /dev/null
@@ -1,39 +0,0 @@
-/*
- *  Copyright 2016 Alexey Andreev.
- *
- *  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.
- */
-package org.teavm.wasm.decompile;
-
-import com.carrotsearch.hppc.IntObjectMap;
-import com.carrotsearch.hppc.IntObjectOpenHashMap;
-
-public final class ContextUtils {
-    private ContextUtils() {
-    }
-
-    public static void withLabels(Context context, IntObjectMap<Label> labels) {
-        IntObjectMap<Label> undo = new IntObjectOpenHashMap<>();
-        for (int node : labels.keys().toArray()) {
-            undo.put(node, context.getLabel(node));
-        }
-        context.push(() -> withLabelsImpl(context, undo));
-        withLabelsImpl(context, labels);
-    }
-
-    private static void withLabelsImpl(Context context, IntObjectMap<Label> labels) {
-        for (int node : labels.keys().toArray()) {
-            context.setLabel(node, labels.get(node));
-        }
-    }
-}
diff --git a/core/src/main/java/org/teavm/wasm/decompile/DecompileSupport.java b/core/src/main/java/org/teavm/wasm/decompile/DecompileSupport.java
new file mode 100644
index 000000000..d354b0ee4
--- /dev/null
+++ b/core/src/main/java/org/teavm/wasm/decompile/DecompileSupport.java
@@ -0,0 +1,161 @@
+/*
+ *  Copyright 2016 Alexey Andreev.
+ *
+ *  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.
+ */
+package org.teavm.wasm.decompile;
+
+import org.teavm.model.instructions.BinaryBranchingInstruction;
+import org.teavm.model.instructions.BranchingCondition;
+import org.teavm.model.instructions.BranchingInstruction;
+import org.teavm.model.util.VariableType;
+import org.teavm.wasm.model.WasmLocal;
+import org.teavm.wasm.model.WasmType;
+import org.teavm.wasm.model.expression.WasmExpression;
+import org.teavm.wasm.model.expression.WasmFloat32Constant;
+import org.teavm.wasm.model.expression.WasmFloat64Constant;
+import org.teavm.wasm.model.expression.WasmFloatBinary;
+import org.teavm.wasm.model.expression.WasmFloatBinaryOperation;
+import org.teavm.wasm.model.expression.WasmFloatType;
+import org.teavm.wasm.model.expression.WasmInt32Constant;
+import org.teavm.wasm.model.expression.WasmInt64Constant;
+import org.teavm.wasm.model.expression.WasmIntBinary;
+import org.teavm.wasm.model.expression.WasmIntBinaryOperation;
+import org.teavm.wasm.model.expression.WasmIntType;
+import org.teavm.wasm.model.expression.WasmLocalReference;
+
+final class DecompileSupport {
+    private DecompileSupport() {
+    }
+
+    public static WasmExpression getCondition(BranchingInstruction instruction, WasmLocal local, VariableType type) {
+        WasmExpression operand = new WasmLocalReference(local);
+
+        WasmExpression condition;
+        switch (type) {
+            case FLOAT:
+                condition = new WasmFloatBinary(WasmFloatType.FLOAT32, getFloatCondition(instruction.getCondition()),
+                        operand, new WasmFloat32Constant(0));
+                break;
+            case DOUBLE:
+                condition = new WasmFloatBinary(WasmFloatType.FLOAT64, getFloatCondition(instruction.getCondition()),
+                        operand, new WasmFloat64Constant(0));
+                break;
+            case INT:
+                condition = new WasmIntBinary(WasmIntType.INT32, getIntCondition(instruction.getCondition()),
+                        operand, new WasmInt32Constant(0));
+                break;
+            case LONG:
+                condition = new WasmIntBinary(WasmIntType.INT64, getIntCondition(instruction.getCondition()),
+                        operand, new WasmInt64Constant(0));
+                break;
+            default:
+                condition = new WasmIntBinary(WasmIntType.INT32, getReferenceCondition(instruction.getCondition()),
+                        operand, new WasmInt32Constant(0));
+                break;
+        }
+
+        return operand;
+    }
+
+    public static WasmExpression getCondition(BinaryBranchingInstruction instruction, WasmLocal first,
+            WasmLocal second) {
+        WasmExpression a = new WasmLocalReference(first);
+        WasmExpression b = new WasmLocalReference(second);
+
+        WasmExpression condition;
+        switch (instruction.getCondition()) {
+            case REFERENCE_EQUAL:
+            case EQUAL:
+                condition = new WasmIntBinary(WasmIntType.INT32, WasmIntBinaryOperation.EQ, a, b);
+                break;
+            case REFERENCE_NOT_EQUAL:
+            case NOT_EQUAL:
+                condition = new WasmIntBinary(WasmIntType.INT32, WasmIntBinaryOperation.NE, a, b);
+                break;
+            default:
+                throw new IllegalArgumentException(instruction.getCondition().toString());
+        }
+
+        return condition;
+    }
+
+    private static WasmFloatBinaryOperation getFloatCondition(BranchingCondition condition) {
+        switch (condition) {
+            case EQUAL:
+                return WasmFloatBinaryOperation.EQ;
+            case NOT_EQUAL:
+                return WasmFloatBinaryOperation.NE;
+            case GREATER:
+                return WasmFloatBinaryOperation.GT;
+            case GREATER_OR_EQUAL:
+                return WasmFloatBinaryOperation.GE;
+            case LESS:
+                return WasmFloatBinaryOperation.LT;
+            case LESS_OR_EQUAL:
+                return WasmFloatBinaryOperation.LE;
+            case NULL:
+            case NOT_NULL:
+                break;
+        }
+        throw new IllegalArgumentException(condition.toString());
+    }
+
+    private static WasmIntBinaryOperation getIntCondition(BranchingCondition condition) {
+        switch (condition) {
+            case EQUAL:
+                return WasmIntBinaryOperation.EQ;
+            case NOT_EQUAL:
+                return WasmIntBinaryOperation.NE;
+            case GREATER:
+                return WasmIntBinaryOperation.GT_SIGNED;
+            case GREATER_OR_EQUAL:
+                return WasmIntBinaryOperation.GE_SIGNED;
+            case LESS:
+                return WasmIntBinaryOperation.LT_SIGNED;
+            case LESS_OR_EQUAL:
+                return WasmIntBinaryOperation.LE_SIGNED;
+            case NULL:
+            case NOT_NULL:
+                break;
+        }
+        throw new IllegalArgumentException(condition.toString());
+    }
+
+    private static WasmIntBinaryOperation getReferenceCondition(BranchingCondition condition) {
+        switch (condition) {
+            case NULL:
+                return WasmIntBinaryOperation.EQ;
+            case NOT_NULL:
+                return WasmIntBinaryOperation.NE;
+            default:
+                break;
+        }
+        throw new IllegalArgumentException(condition.toString());
+    }
+
+    public static WasmType mapType(VariableType type) {
+        switch (type) {
+            case INT:
+                return WasmType.INT32;
+            case LONG:
+                return WasmType.INT64;
+            case FLOAT:
+                return WasmType.FLOAT32;
+            case DOUBLE:
+                return WasmType.FLOAT64;
+            default:
+                return WasmType.INT32;
+        }
+    }
+}
diff --git a/core/src/main/java/org/teavm/wasm/decompile/WasmDecompiler.java b/core/src/main/java/org/teavm/wasm/decompile/WasmDecompiler.java
index 59fa058ef..3dcf8e83a 100644
--- a/core/src/main/java/org/teavm/wasm/decompile/WasmDecompiler.java
+++ b/core/src/main/java/org/teavm/wasm/decompile/WasmDecompiler.java
@@ -15,40 +15,81 @@
  */
 package org.teavm.wasm.decompile;
 
+import com.carrotsearch.hppc.IntObjectMap;
+import com.carrotsearch.hppc.IntObjectOpenHashMap;
+import java.util.Arrays;
+import java.util.List;
 import org.teavm.common.DominatorTree;
 import org.teavm.common.Graph;
 import org.teavm.common.GraphUtils;
+import org.teavm.common.IntegerArray;
 import org.teavm.common.Loop;
 import org.teavm.common.LoopGraph;
+import org.teavm.model.BasicBlock;
+import org.teavm.model.Instruction;
+import org.teavm.model.MethodReference;
 import org.teavm.model.Program;
+import org.teavm.model.instructions.BinaryBranchingInstruction;
+import org.teavm.model.instructions.BranchingInstruction;
 import org.teavm.model.util.ProgramUtils;
+import org.teavm.model.util.TypeInferer;
+import org.teavm.model.util.VariableType;
+import org.teavm.wasm.model.WasmFunction;
+import org.teavm.wasm.model.WasmLocal;
+import org.teavm.wasm.model.WasmType;
 import org.teavm.wasm.model.expression.WasmBlock;
+import org.teavm.wasm.model.expression.WasmConditional;
 import org.teavm.wasm.model.expression.WasmExpression;
+import org.teavm.wasm.model.expression.WasmIntBinary;
+import org.teavm.wasm.model.expression.WasmIntBinaryOperation;
+import org.teavm.wasm.model.expression.WasmIntType;
+import org.teavm.wasm.model.expression.WasmLocalReference;
 
 public class WasmDecompiler {
+    private WasmFunction function;
     private Program program;
     private LoopGraph cfg;
     private DominatorTree dom;
     private Graph domGraph;
     private Label[] labels;
-    private WasmExpression[] blockExpressions;
+    private TypeInferer typeInferer;
     private Step[] stack;
     private int stackTop;
 
-    public void decompile(Program program) {
+    public void decompile(Program program, MethodReference methodReference, WasmFunction function) {
+        this.function = function;
         this.program = program;
-        prepare();
-        push(new EnterStep(0));
+        prepare(methodReference);
+        deferEnter(0, function.getBody());
         run();
     }
 
-    private void prepare() {
+    private void prepare(MethodReference methodReference) {
         cfg = new LoopGraph(ProgramUtils.buildControlFlowGraph(program));
         dom = GraphUtils.buildDominatorTree(cfg);
         domGraph = GraphUtils.buildDominatorGraph(dom, cfg.size());
         labels = new Label[cfg.size()];
-        blockExpressions = new WasmExpression[cfg.size()];
         stack = new Step[cfg.size() * 4];
+        typeInferer = new TypeInferer();
+        typeInferer.inferTypes(program, methodReference);
+
+        int maxLocal = 0;
+        for (int i = 0; i < program.variableCount(); ++i) {
+            maxLocal = Math.max(maxLocal, program.variableAt(i).getRegister());
+        }
+
+        WasmType[] types = new WasmType[maxLocal];
+        for (int i = 0; i < program.variableCount(); ++i) {
+            int register = program.variableAt(i).getRegister();
+            if (types[register] == null) {
+                types[register] = DecompileSupport.mapType(typeInferer.typeOf(i));
+            }
+        }
+
+        for (int i = 0; i < maxLocal; ++i) {
+            WasmType type = types[i];
+            function.getLocalVariables().add(new WasmLocal(type != null ? type : WasmType.INT32, null));
+        }
     }
 
     private void run() {
@@ -61,75 +102,129 @@ public class WasmDecompiler {
         stack[stackTop++] = step;
     }
 
-    private class EnterStep implements Step {
-        private int index;
+    private void deferEnter(int node, List<WasmExpression> expressions) {
+        push(() -> enter(node, expressions));
+    }
 
-        public EnterStep(int index) {
-            this.index = index;
+    private void enter(int node, List<WasmExpression> expressions) {
+        Loop loop = cfg.loopAt(node);
+        if (loop != null && loop.getHead() == node) {
+            expressions = enterLoop(loop, expressions);
         }
 
-        @Override
-        public void perform() {
-            Loop loop = cfg.loopAt(index);
-            if (loop != null && loop.getHead() == index) {
-                enterLoop();
-            } else if (cfg.outgoingEdgesCount(index) == 1) {
-                enterOrdinaryBlock();
-            } else {
-                enterBranching();
+        DecompilationVisitor decompilationVisitor = new DecompilationVisitor(expressions, context);
+        compileInstructions(node, decompilationVisitor);
+
+        int successors = domGraph.outgoingEdgesCount(node);
+        if (successors == 1) {
+            deferEnter(domGraph.outgoingEdges(node)[0], expressions);
+        } else if (successors == 0) {
+            BasicBlock block = program.basicBlockAt(node);
+            block.getLastInstruction().acceptVisitor(decompilationVisitor);
+        } else {
+            compileFork(node, expressions);
+        }
+    }
+
+    private void compileInstructions(int node, DecompilationVisitor decompilationVisitor) {
+        BasicBlock block = program.basicBlockAt(node);
+        int lastInstructionIndex = block.getInstructions().size() - 1;
+        for (int i = 0; i < lastInstructionIndex; ++i) {
+            block.getInstructions().get(i).acceptVisitor(decompilationVisitor);
+        }
+    }
+
+    private List<WasmExpression> enterLoop(Loop loop, List<WasmExpression> expressions) {
+        WasmBlock wasmLoop = new WasmBlock(true);
+        List<WasmExpression> innerExpressions = wasmLoop.getBody();
+        expressions.add(wasmLoop);
+        LoopExitStep exitStep = new LoopExitStep(expressions, wasmLoop);
+        push(exitStep);
+
+        IntObjectMap<Label> newLabels = new IntObjectOpenHashMap<>();
+        int[] exits = findLoopExits(loop);
+        Label breakLabel = exitStep.createBreakLabel();
+        for (int exit : exits) {
+            newLabels.put(exit, breakLabel);
+        }
+        newLabels.put(loop.getHead(), exitStep.createContinueLabel());
+        withLabels(newLabels);
+
+        return innerExpressions;
+    }
+
+    private int[] findLoopExits(Loop loop) {
+        IntegerArray exits = new IntegerArray(2);
+        for (int i = 0; i < cfg.size(); ++i) {
+            Loop nodeLoop = cfg.loopAt(i);
+            if (nodeLoop != null && nodeLoop.isChildOf(loop)) {
+                for (int successor : cfg.outgoingEdges(i)) {
+                    Loop successorLoop = cfg.loopAt(successor);
+                    if (successorLoop == null || !successorLoop.isChildOf(loop)) {
+                        exits.add(i);
+                        break;
+                    }
+                }
             }
         }
+        return exits.getAll();
+    }
 
-        private void enterLoop() {
-
-        }
-
-        private void enterOrdinaryBlock() {
-
-        }
-
-        private void enterBranching() {
-
+    private void compileFork(int node, List<WasmExpression> expressions) {
+        Instruction instruction = program.basicBlockAt(node).getLastInstruction();
+        if (instruction instanceof BranchingInstruction) {
+            compileFork(node, expressions, (BranchingInstruction) instruction);
+        } else if (instruction instanceof BinaryBranchingInstruction) {
+            compileFork(node, expressions, (BinaryBranchingInstruction) instruction);
         }
     }
 
-    private class LoopContinueLabel implements Label {
-        private int index;
-        private WasmBlock wrapper;
+    private void compileFork(int node, List<WasmExpression> expressions, BranchingInstruction instruction) {
+        WasmLocal local = function.getLocalVariables().get(instruction.getOperand().getRegister());
+        WasmExpression operand = new WasmLocalReference(local);
+        VariableType operandType = typeInferer.typeOf(instruction.getOperand().getIndex());
+        WasmExpression condition = DecompileSupport.getCondition(instruction, local, operandType);
+        compileIf(node, expressions, condition, instruction.getConsequent().getIndex(),
+                instruction.getAlternative().getIndex());
+    }
 
-        public LoopContinueLabel(int index) {
-            this.index = index;
-        }
+    private void compileFork(int node, List<WasmExpression> expressions, BinaryBranchingInstruction instruction) {
+        WasmLocal a = function.getLocalVariables().get(instruction.getFirstOperand().getIndex());
+        WasmLocal b = function.getLocalVariables().get(instruction.getSecondOperand().getIndex());
+        WasmExpression condition = DecompileSupport.getCondition(instruction, a, b);
+        compileIf(node, expressions, condition, instruction.getConsequent().getIndex(),
+                instruction.getAlternative().getIndex());
+    }
 
-        @Override
-        public WasmBlock getTarget() {
-            if (wrapper == null) {
-                wrapper = new WasmBlock(false);
-                wrapper.getBody().add(blockExpressions[index]);
-                blockExpressions[index] = wrapper;
-            }
-            return wrapper;
+    private void compileIf(int node, List<WasmExpression> expressions, WasmExpression condition,
+            int thenNode, int elseNode) {
+        boolean ownsThen = dom.directlyDominates(node, thenNode);
+        boolean ownsElse = dom.directlyDominates(node, elseNode);
+        int[] exits = Arrays.stream(domGraph.outgoingEdges(node))
+                .filter(n -> n != thenNode && n != elseNode)
+                .toArray();
+
+        if (ownsThen && ownsElse) {
+            WasmConditional conditional = new WasmConditional(condition);
+            expressions.add(conditional);
+            compileBranch(conditional.getElseBlock(), elseNode, exits);
+            compileBranch(conditional.getThenBlock(), thenNode, exits);
         }
     }
 
-    private class BreakLabel implements Label {
-        private WasmBlock target;
 
-        public BreakLabel(WasmBlock target) {
-            this.target = target;
-        }
-
-        @Override
-        public WasmBlock getTarget() {
-            return null;
+    private void withLabels(IntObjectMap<Label> labels) {
+        IntObjectMap<Label> undo = new IntObjectOpenHashMap<>();
+        for (int node : labels.keys().toArray()) {
+            undo.put(node, this.labels[node]);
         }
+        push(() -> withLabelsImpl(undo));
+        withLabelsImpl(labels);
     }
 
-    private interface Step {
-        void perform();
-    }
-
-    private interface Label {
-        WasmBlock getTarget();
+    private void withLabelsImpl(IntObjectMap<Label> labels) {
+        for (int node : labels.keys().toArray()) {
+            this.labels[node] = labels.get(node);
+        }
     }
 }