Reenable the duplicated test at the bottom of for and while loops. It...

src/codegen-ia32.cc

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2210 matching lines @@
           LoadCondition(node->cond(), NOT_INSIDE_TYPEOF, &dest, true);
         }
         if (node->break_target()->is_linked()) {
           node->break_target()->Bind();
         }
       }
       break;
     }
 
     case LoopStatement::WHILE_LOOP: {
-      // TODO(260): This flag controls whether to duplicate the test
-      // at the bottom of the loop.  Replace it with a better
-      // indication of when it is safe to do so.
-      static const bool test_at_bottom = false;
+      // Do not duplicate conditions with function literal
+      // subexpressions.  This can cause us to compile the function
+      // literal twice.
+      bool test_at_bottom = !node->has_function_literal();
 
-      JumpTarget body(this);  // Initialized as forward-only.
       IncrementLoopNesting();
 
       // If the condition is always false and has no side effects, we
       // do not need to compile anything.
       if (info == ALWAYS_FALSE) break;
 
+      JumpTarget body;
+      if (test_at_bottom) {
+        body.Initialize(this, JumpTarget::BIDIRECTIONAL);
+      } else {
+        body.Initialize(this);
+      }
+
       // Based on the condition analysis, compile the test as necessary.
       if (info == ALWAYS_TRUE) {
         // We will not compile the test expression.  Label the top of
         // the loop with the continue target.
         node->continue_target()->Initialize(this, JumpTarget::BIDIRECTIONAL);
         node->continue_target()->Bind();
       } else {
         ASSERT(info == DONT_KNOW);  // ALWAYS_FALSE cannot reach here.
         if (test_at_bottom) {
           // Continue is the test at the bottom, no need to label the
           // test at the top.  The body is a backward target.
           node->continue_target()->Initialize(this);
-          body.make_bidirectional();
         } else {
           // Label the test at the top as the continue target.  The
           // body is a forward-only target.
           node->continue_target()->Initialize(this, JumpTarget::BIDIRECTIONAL);
           node->continue_target()->Bind();
         }
         // Compile the test with the body as the true target and
         // preferred fall-through and with the break target as the
         // false target.
         ControlDestination dest(&body, node->break_target(), true);
@@ skipping 48 matching lines @@
 
       // The break target may be already bound (by the condition), or
       // there may not be a valid frame.  Bind it only if needed.
       if (node->break_target()->is_linked()) {
         node->break_target()->Bind();
       }
       break;
     }
 
     case LoopStatement::FOR_LOOP: {
-      // TODO(260): This flag controls whether to duplicate the test
-      // at the bottom of the loop.  Replace it with a better
-      // indication of when it is safe to do so.
-      static const bool test_at_bottom = false;
-
-      JumpTarget loop(this, JumpTarget::BIDIRECTIONAL);
-      JumpTarget body(this);
+      // Do not duplicate conditions with function literal
+      // subexpressions.  This can cause us to compile the function
+      // literal twice.
+      bool test_at_bottom = !node->has_function_literal();
 
       // Compile the init expression if present.
       if (node->init() != NULL) {
         Visit(node->init());
       }
 
       IncrementLoopNesting();
 
       // If the condition is always false and has no side effects, we
       // do not need to compile anything else.
       if (info == ALWAYS_FALSE) break;
 
+      // Target for backward edge if no test at the bottom, otherwise
+      // unused.
+      JumpTarget loop(this, JumpTarget::BIDIRECTIONAL);
+
+      // Target for backward edge if there is a test at the bottom,
+      // otherwise used as target for test at the top.
+      JumpTarget body;
+      if (test_at_bottom) {
+        body.Initialize(this, JumpTarget::BIDIRECTIONAL);
+      } else {
+        body.Initialize(this);
+      }
+
       // Based on the condition analysis, compile the test as necessary.
       if (info == ALWAYS_TRUE) {
         // We will not compile the test expression.  Label the top of
         // the loop.
         if (node->next() == NULL) {
           // Use the continue target if there is no update expression.
           node->continue_target()->Initialize(this, JumpTarget::BIDIRECTIONAL);
           node->continue_target()->Bind();
         } else {
           // Otherwise use the backward loop target.
@@ skipping 4582 matching lines @@
 
   // Slow-case: Go through the JavaScript implementation.
   __ bind(&slow);
   __ InvokeBuiltin(Builtins::INSTANCE_OF, JUMP_FUNCTION);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal