From 3d12aed4467bd9c28c587f38946a61b2f8a6c8d9 Mon Sep 17 00:00:00 2001
From: konsoletyper <konsoletyper@gmail.com>
Date: Tue, 1 Oct 2013 22:10:25 +0400
Subject: [PATCH] Adds phi instruction eliminator

---
 .../teavm/javascript/MethodDecompiler.java    | 21 +++++++++++++++
 .../teavm/javascript/StatementGenerator.java  | 27 ++++++++++++++++---
 2 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/teavm-core/src/main/java/org/teavm/javascript/MethodDecompiler.java b/teavm-core/src/main/java/org/teavm/javascript/MethodDecompiler.java
index db526a544..c36e60030 100644
--- a/teavm-core/src/main/java/org/teavm/javascript/MethodDecompiler.java
+++ b/teavm-core/src/main/java/org/teavm/javascript/MethodDecompiler.java
@@ -87,6 +87,7 @@ public class MethodDecompiler {
         generator.program = program;
         generator.blockMap = blockMap;
         generator.indexer = indexer;
+        generator.outgoings = getPhiOutgoings(program);
         parentNode = codeTree.getRoot();
         currentNode = parentNode.getFirstChild();
         for (int i = 0; i < this.graph.size(); ++i) {
@@ -128,6 +129,26 @@ public class MethodDecompiler {
         return renderable;
     }
 
+    private Incoming[][] getPhiOutgoings(Program program) {
+        List<List<Incoming>> outgoings = new ArrayList<>();
+        for (int i = 0; i < program.basicBlockCount(); ++i) {
+            outgoings.add(new ArrayList<Incoming>());
+        }
+        for (int i = 0; i < program.basicBlockCount(); ++i) {
+            BasicBlock basicBlock = program.basicBlockAt(i);
+            for (Phi phi : basicBlock.getPhis()) {
+                for (Incoming incoming : phi.getIncomings()) {
+                    outgoings.get(incoming.getSource().getIndex()).add(incoming);
+                }
+            }
+        }
+        Incoming[][] result = new Incoming[outgoings.size()][];
+        for (int i = 0; i < outgoings.size(); ++i) {
+            result[i] = outgoings.get(i).toArray(new Incoming[0]);
+        }
+        return result;
+    }
+
     private List<Block> createBlocks(int start) {
         List<Block> result = new ArrayList<>();
         while (currentNode != null && currentNode.getStart() == start) {
diff --git a/teavm-core/src/main/java/org/teavm/javascript/StatementGenerator.java b/teavm-core/src/main/java/org/teavm/javascript/StatementGenerator.java
index 87754cb95..077b9d35b 100644
--- a/teavm-core/src/main/java/org/teavm/javascript/StatementGenerator.java
+++ b/teavm-core/src/main/java/org/teavm/javascript/StatementGenerator.java
@@ -21,6 +21,7 @@ public class StatementGenerator implements InstructionVisitor {
     MethodDecompiler.Block[] blockMap;
     Program program;
     ClassHolderSource classSource;
+    Incoming[][] outgoings;
 
     @Override
     public void visit(EmptyInstruction insn) {
@@ -527,7 +528,7 @@ public class StatementGenerator implements InstructionVisitor {
         assign(castToInteger(Expr.binary(op, Expr.var(first), Expr.var(second))), result);
     }
 
-    private Statement generateJumpStatement(BasicBlock target) {
+    private Statement generateJumpStatementWithoutPhis(BasicBlock target) {
         if (nextBlock == target) {
             return null;
         }
@@ -543,8 +544,24 @@ public class StatementGenerator implements InstructionVisitor {
         }
     }
 
-    private Statement generateJumpStatement(SwitchStatement stmt, int target) {
-        Statement body = generateJumpStatement(program.basicBlockAt(target));
+    private Statement wrapWithPhis(Statement rawJump) {
+        SequentialStatement seq = new SequentialStatement();
+        for (Incoming outgoing : outgoings[currentBlock.getIndex()]) {
+            seq.getSequence().add(Statement.assign(Expr.var(outgoing.getPhi().getReceiver().getIndex()),
+                    Expr.var(outgoing.getValue().getIndex())));
+        }
+        if (rawJump != null) {
+            seq.getSequence().add(rawJump);
+        }
+        return !seq.getSequence().isEmpty() ? seq : null;
+    }
+
+    private Statement generateJumpStatement(BasicBlock target) {
+        return wrapWithPhis(generateJumpStatementWithoutPhis(target));
+    }
+
+    private Statement generateJumpStatementWithoutPhis(SwitchStatement stmt, int target) {
+        Statement body = generateJumpStatementWithoutPhis(program.basicBlockAt(target));
         if (body == null) {
             BreakStatement breakStmt = new BreakStatement();
             breakStmt.setTarget(stmt);
@@ -553,6 +570,10 @@ public class StatementGenerator implements InstructionVisitor {
         return body;
     }
 
+    private Statement generateJumpStatement(SwitchStatement stmt, int target) {
+        return wrapWithPhis(generateJumpStatementWithoutPhis(stmt, target));
+    }
+
     private void branch(Expr condition, BasicBlock consequentBlock, BasicBlock alternativeBlock) {
         Statement consequent = generateJumpStatement(consequentBlock);
         Statement alternative = generateJumpStatement(alternativeBlock);