Change labeled statement to use visitSubGraph for its body instead of marking its "exit block" spec…

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 bc9aa4aec4be6c1ca8b4f06fd72261685675fb49..282094fe74e0bc898d0e95dc419068dc30cc9102 100644
--- a/frog/leg/ssa/codegen.dart
+++ b/frog/leg/ssa/codegen.dart
@@ -161,7 +161,7 @@ class SsaCodeGenerator implements HVisitor {
   void visitSubGraph(SubGraph newSubGraph) {
     SubGraph oldSubGraph = subGraph;
     subGraph = newSubGraph;
-    visitBasicBlock(subGraph.start);
+    iterateBasicBlock(subGraph.start);
     subGraph = oldSubGraph;
   }
 
@@ -239,45 +239,42 @@ class SsaCodeGenerator implements HVisitor {
 
   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");
+
+    addIndentation();
+    for (SourceString label in labeledBlockInfo.labels) {
+      addLabel(label);
+      buffer.add(":");
     }
+    buffer.add("{\n");
+    indent++;
+
+    visitSubGraph(labeledBlockInfo.body);
+
+    indent--;
+    addIndentation();
+    buffer.add("}\n");
+
+    visitBasicBlock(labeledBlockInfo.joinBlock);
   }
 
 
   visitBasicBlock(HBasicBlock node) {
     if (!subGraph.contains(node)) return;
 
-    currentBlock = node;
-
     if (node.hasLabeledBlockInformation()) {
       handleLabeledBlock(node);
-    } else if (currentBlock.isLoopHeader()) {
+      return;
+    }
+    iterateBasicBlock(node);
+  }
+
+  iterateBasicBlock(HBasicBlock node) {

[ngeoffray, 2012/03/05 14:12:48]

Was this change (adding iterateBasicBlock) necessary? If not, I prefer keeping
one method for now.

[Lasse Reichstein Nielsen, 2012/03/05 14:16:49]

Sadly, yes, something is necessary, but I'm not entirely sure what.
visitBasicBlock calls handleLabeledBlock, which calls visitSubGraph, which calls
back to visitBlock.
To break this loop, I split the main visitBasicBlock into the part that
dispatches on the block annotation and the part that does the real work. But
thinking more about it, I'm not sure it's good enough. If a labeled statement is
a branch of an if, it'll fail. Back to the drawing board. :(

+    currentBlock = node;
+    if (node.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) {
       if (instruction is HGoto || instruction is HExit || instruction is HTry) {