Fix for do/while: if there are phi copies after the condition, emit the non-pretty while loop.

sdk/lib/_internal/compiler/implementation/ssa/codegen.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of ssa;
 
 class SsaCodeGeneratorTask extends CompilerTask {
 
   final JavaScriptBackend backend;
 
@@ skipping 1011 matching lines @@
             generateStatements(info.updates);
           } else {
             visitBodyIgnoreLabels(info);
           }
           currentContainer = oldContainer;
           body = unwrapStatement(body);
           loop = new js.While(jsCondition, body);
         }
         break;
       case HLoopBlockInformation.DO_WHILE_LOOP:
+        CopyHandler handler = variableNames.getCopyHandler(info.end);

[floitsch, 2012/11/07 09:59:04]

Add comment explaining why this is necessary.

[ngeoffray, 2012/11/07 10:04:49]

Done.

+        if (handler != null && !handler.isEmpty) return false;
         // Generate do-while loop in all cases.

[floitsch, 2012/11/07 09:59:04]

Remove comment or:
Generate do-while loop in all other cases.

[ngeoffray, 2012/11/07 10:04:49]

Comment removed.

         if (info.initializer != null) {
           generateStatements(info.initializer);
         }
         js.Block oldContainer = currentContainer;
         js.Statement body = new js.Block.empty();
         currentContainer = body;
         if (!isConditionExpression || info.updates != null) {
           wrapLoopBodyForContinue(info);
         } else {
           visitBodyIgnoreLabels(info);
@@ skipping 276 matching lines @@
   void iterateBasicBlock(HBasicBlock node) {
     HInstruction instruction = node.first;
     while (!identical(instruction, node.last)) {
       if (instruction is HTypeGuard || instruction is HBailoutTarget) {
         visit(instruction);
       } else if (!isGenerateAtUseSite(instruction)) {
         define(instruction);
       }
       instruction = instruction.next;
     }
-    assignPhisOfSuccessors(node);
+    if (instruction is HLoopBranch) {
+      HLoopBranch branch = instruction;
+      // If the loop is a do/while loop, the phi updates must happen
+      // after the evaluation of the condition.
+      if (!branch.isDoWhile()) {
+        assignPhisOfSuccessors(node);
+      }
+    } else {
+      assignPhisOfSuccessors(node);
+    }
     visit(instruction);
   }
 
   visitInvokeBinary(HInvokeBinary node, String op) {
     if (node.isBuiltin(types)) {
       use(node.left);
       js.Expression jsLeft = pop();
       use(node.right);
       push(new js.Binary(op, jsLeft, pop()), node);
     } else {
@@ skipping 572 matching lines @@
       // to the code that called [visitSubGraph].
       if (isGeneratingExpression) {
         use(node.inputs[0]);
       }
       return;
     }
     HBasicBlock branchBlock = currentBlock;
     handleLoopCondition(node);
     List<HBasicBlock> dominated = currentBlock.dominatedBlocks;
     // For a do while loop, the body has already been visited.
     if (!node.isDoWhile()) {

[floitsch, 2012/11/07 09:59:04]

Invert the test, so that we don't have the "!".

[ngeoffray, 2012/11/07 10:04:49]

Done.

       visitBasicBlock(dominated[0]);
+    } else {
+      // Now that the condition has been evaluated, we can update the
+      // phis of a do/while loop.
+      assignPhisOfSuccessors(node.block);
     }
     endLoop(node.block);
 
     // If the branch does not dominate the code after the loop, the
     // dominator will visit it.
     if (!identical(branchBlock.successors[1].dominator, branchBlock)) return;
 
     visitBasicBlock(branchBlock.successors[1]);
     // With labeled breaks we can have more dominated blocks.
     if (dominated.length >= 3) {
@@ skipping 840 matching lines @@
     oldContainerStack.add(currentContainer);
     currentContainer = new js.Block.empty();
   }
 
   void endLoop(HBasicBlock block) {
     js.Statement body = currentContainer;
     currentContainer = oldContainerStack.removeLast();
     body = unwrapStatement(body);
     js.While loop = new js.While(newLiteralBool(true), body);
 
-    HLoopInformation info = block.loopInformation;
+    HBasicBlock header = block.isLoopHeader() ? block : block.parentLoopHeader;
+    HLoopInformation info = header.loopInformation;
     attachLocationRange(loop,
                         info.loopBlockInformation.sourcePosition,
                         info.loopBlockInformation.endSourcePosition);
     pushStatement(wrapIntoLabels(loop, info.labels));
   }
 
   void handleLoopCondition(HLoopBranch node) {
     use(node.inputs[0]);
-    pushStatement(new js.If.noElse(pop(), new js.Break(null)), node);
+    js.Expression test = new js.Prefix('!', pop());
+    js.Statement then = new js.Break(null);
+    pushStatement(new js.If.noElse(test, then), node);
   }
 
 
   void preLabeledBlock(HLabeledBlockInformation labeledBlockInfo) {
   }
 
   void startLabeledBlock(HLabeledBlockInformation labeledBlockInfo) {
   }
 
   void endLabeledBlock(HLabeledBlockInformation labeledBlockInfo) {
@@ skipping 340 matching lines @@
   if (leftType.canBeNull() && rightType.canBeNull()) {
     if (left.isConstantNull() || right.isConstantNull() ||
         (leftType.isPrimitive() && leftType == rightType)) {
       return '==';
     }
     return null;
   } else {
     return '===';
   }
 }