Support break and labeled statements.

frog/leg/ssa/codegen.dart

Index: frog/leg/ssa/codegen.dart
diff --git a/frog/leg/ssa/codegen.dart b/frog/leg/ssa/codegen.dart
index 222ced5db3b35fc15fb38744d745150a70897a4d..89241acdfaabc3c94cd9c6dc6e47d44ec86d0f52 100644
--- a/frog/leg/ssa/codegen.dart
+++ b/frog/leg/ssa/codegen.dart
@@ -211,12 +211,43 @@ class SsaCodeGenerator implements HVisitor {
     return node.accept(this);
   }
 
+  void handleLabeledBlock(HBasicBlock node) {
+    HLabeledBlockInformation labeledBlockInfo = node.labeledBlockInformation;
+    if (labeledBlockInfo.start === node) {
+      addIndentation();
+      for (SourceString label in labeledBlockInfo.labels) {
+        addLabel(label);
+        buffer.add(":");
+      }
+      buffer.add("{\n");
+      indent++;
+    } else {
+      assert(labeledBlockInfo.end === node);
+      assert((){
+        // Check that this block is (transitively) dominated by the start block.
+        HBasicBlock block = node;
+        while (block.dominator !== null) {
+          block = block.dominator;
+          if (block === labeledBlockInfo.start) return true;
+        }
+        return false;
+      });
+      indent--;
+      addIndentation();
+      buffer.add("}\n");
+    }
+  }
+
   visitBasicBlock(HBasicBlock node) {
     currentBlock = node;
 
-    // While loop will be closed by the conditional loop-branch.
-    // TODO(floitsch): HACK HACK HACK.
-    if (currentBlock.isLoopHeader()) beginLoop(node);
+    if (node.hasLabeledBlockInformation()) {
+      handleLabeledBlock(node);
+    } else if (currentBlock.isLoopHeader()) {
+      // While loop will be closed by the conditional loop-branch.
+      // TODO(floitsch): HACK HACK HACK.
+      beginLoop(node);
+    }
 
     HInstruction instruction = node.first;
     while (instruction != null) {
@@ -350,6 +381,33 @@ class SsaCodeGenerator implements HVisitor {
     visitBasicBlock(dominated[0]);
   }
 
+  void addLabel(SourceString label) {

[floitsch, 2012/02/20 19:01:54]

to many addLabels and similar: sometimes with prefixed '$' sometimes with
label.toString, or with stringValue...
If they should be different make this clearer, if not share the code.

[Lasse Reichstein Nielsen, 2012/02/21 13:53:56]

There are two addLabels, one for optimized code (and being the default, it is in
SsaCodeGenerator), and one overriding it in SsaUnoptimizedCodeGenerator. I'll
add comments describing the difference.

+    buffer.add(label.toString());
+  }
+
+  visitBreak(HBreak node) {
+    assert(currentBlock.successors.length == 1);
+    addIndentation();
+    buffer.add("break");
+    if (node.label !== null) {
+      buffer.add(" ");
+      addLabel(node.label);
+    }
+    buffer.add(";\n");
+    List<HBasicBlock> dominated = currentBlock.dominatedBlocks;
+    // No block finishing with a 'throw' can have more than

[floitsch, 2012/02/20 19:01:54]

s/throw/break.

[Lasse Reichstein Nielsen, 2012/02/21 13:53:56]

Done.

+    // one dominated block (since it has only one successor).
+    // If the successor is dominated by another block, then the other block
+    // is responsible for visiting the successor.
+    if (dominated.isEmpty()) return;
+    if (dominated.length > 2) unreachable();
+    if (dominated.length == 2 && currentBlock !== currentGraph.entry) {
+      unreachable();
+    }
+    assert(dominated[0] == currentBlock.successors[0]);
+    visitBasicBlock(dominated[0]);
+  }
+
   visitTry(HTry node) {
     addIndentation();
     buffer.add('try {\n');
@@ -427,7 +485,6 @@ class SsaCodeGenerator implements HVisitor {
       // too. The if happens to dominate the exit-block.
       assert(!node.hasElse);
       assert(dominatedCount == 3);
-      assert(dominated.last().isExitBlock());
       visitBasicBlock(dominated[1]);

[floitsch, 2012/02/20 19:01:54]

This doesn't look right. It seems that the if can dominate an arbitrary number
of blocks now (one for each break). And it's the if's job to visit them.

[Lasse Reichstein Nielsen, 2012/02/21 13:53:56]

You are right. All this complication has been reduced to a much simpler, more
generic version (but with fewer asserts, since we don't really know much).

       visitBasicBlock(dominated[2]);
     }
@@ -579,13 +636,11 @@ class SsaCodeGenerator implements HVisitor {
     }
     endLoop(node.block);
     visitBasicBlock(branchBlock.successors[1]);
-    // TODO(floitsch): with labeled breaks we can have more dominated blocks.
-    assert(dominated.length <= 3);
-    if (dominated.length == 3) {
-      // This happens when the body contains a 'return', and the exit-block is
-      // not dominated by a dominator of the while loop.
-      assert(dominated[2].isExitBlock());
-      visitBasicBlock(dominated[2]);
+    // With labeled breaks we can have more dominated blocks.
+    if (dominated.length >= 3) {
+      for (int i = 2; i < dominated.length; i++) {
+        visitBasicBlock(dominated[i]);
+      }
     }
   }
 
@@ -896,6 +951,9 @@ class SsaOptimizedCodeGenerator extends SsaCodeGenerator {
 
   void beginLoop(HBasicBlock block) {
     addIndentation();
+    for (SourceString label in block.loopInformation.labels) {
+      buffer.add("${label.stringValue}:");
+    }
     buffer.add('while (true) {\n');
     indent++;
   }
@@ -1057,6 +1115,10 @@ class SsaUnoptimizedCodeGenerator extends SsaCodeGenerator {
     buffer.add('}\n');  // Close 'switch'.
   }
 
+  void addLabel(SourceString label) {
+    buffer.add("\$$label");
+  }
+
   void beginLoop(HBasicBlock block) {
     // TODO(ngeoffray): Don't put labels on loops that don't bailout.
     String newLabel = pushLabel();
@@ -1065,6 +1127,10 @@ class SsaUnoptimizedCodeGenerator extends SsaCodeGenerator {
     }
 
     addIndentation();
+    for (SourceString label in block.loopInformation.labels) {
+      addLabel(label);
+      buffer.add(":");
+    }
     buffer.add('$newLabel: while (true) {\n');
     indent++;