Fix error in x64 fast smi loops, change 4998.

Review URL: http://codereview.chromium.org/2925012

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5069 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/x64/codegen-x64.cc

@@ -3428,28 +3428,37 @@ void CodeGenerator::GenerateFastSmiLoop(ForStatement* node) {
     CodeForStatementPosition(node);
     Slot* loop_var_slot = loop_var->slot();
     if (loop_var_slot->type() == Slot::LOCAL) {
-      frame_->PushLocalAt(loop_var_slot->index());
+      frame_->TakeLocalAt(loop_var_slot->index());
     } else {
       ASSERT(loop_var_slot->type() == Slot::PARAMETER);
-      frame_->PushParameterAt(loop_var_slot->index());
+      frame_->TakeParameterAt(loop_var_slot->index());
     }
     Result loop_var_result = frame_->Pop();
     if (!loop_var_result.is_register()) {
       loop_var_result.ToRegister();
     }
-
+    Register loop_var_reg = loop_var_result.reg();
+    frame_->Spill(loop_var_reg);
     if (increments) {
-      __ SmiAddConstant(loop_var_result.reg(),
-                        loop_var_result.reg(),
+      __ SmiAddConstant(loop_var_reg,
+                        loop_var_reg,
                         Smi::FromInt(1));
     } else {
-      __ SmiSubConstant(loop_var_result.reg(),
-                        loop_var_result.reg(),
+      __ SmiSubConstant(loop_var_reg,
+                        loop_var_reg,
                         Smi::FromInt(1));
     }
 
-    {
-      __ SmiCompare(loop_var_result.reg(), limit_value);
+    frame_->Push(&loop_var_result);
+    if (loop_var_slot->type() == Slot::LOCAL) {
+      frame_->StoreToLocalAt(loop_var_slot->index());
+    } else {
+      ASSERT(loop_var_slot->type() == Slot::PARAMETER);
+      frame_->StoreToParameterAt(loop_var_slot->index());
+    }
+    frame_->Drop();
+
+    __ SmiCompare(loop_var_reg, limit_value);
     Condition condition;
     switch (compare_op) {
       case Token::LT:
@@ -3470,8 +3479,6 @@ void CodeGenerator::GenerateFastSmiLoop(ForStatement* node) {
     }
     loop.Branch(condition);
   }
-    loop_var_result.Unuse();
-  }
   if (node->break_target()->is_linked()) {
     node->break_target()->Bind();
   }

test/mjsunit/regress/regress-r4998.js

+// Copyright 2010 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
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Test for a broken fast-smi-loop that does not save the incremented value
+// of the loop index.  If this test fails, it loops forever, and times out.
+
+// Flags: --nofull-compiler
+
+// Calling foo() spills the virtual frame.
+function foo() {
+  return;
+}
+
+function bar() {
+  var x1 = 3;
+  var x2 = 3;
+  var x3 = 3;
+  var x4 = 3;
+  var x5 = 3;
+  var x6 = 3;
+  var x7 = 3;
+  var x8 = 3;
+  var x9 = 3;
+  var x10 = 3;
+  var x11 = 3;
+  var x12 = 3;
+  var x13 = 3;
+
+  foo();
+
+  x1 = 257;
+  x2 = 258;
+  x3 = 259;
+  x4 = 260;
+  x5 = 261;
+  x6 = 262;
+  x7 = 263;
+  x8 = 264;
+  x9 = 265;
+  x10 = 266;
+  x11 = 267;
+  x12 = 268;
+  x13 = 269;
+
+  // The loop variable x7 is initialized to 3,
+  // and then MakeMergeable is called on the virtual frame.
+  // MakeMergeable has forced the loop variable x7 to be spilled,
+  // so it is marked as synced
+  // The back edge then merges its virtual frame, which incorrectly
+  // claims that x7 is synced, and does not save the modified
+  // value.
+  for (x7 = 3; x7 < 10; ++x7) {
+    foo();
+  }
+}
+
+bar();
+
+function aliasing() {
+  var x = 3;
+  var j;
+  for (j = 7; j < 11; ++j) {
+    x = j;
+  }
+
+  assertEquals(10, x);
+  assertEquals(11, j);
+}
+
+aliasing();