Fix http://code.google.com/p/v8/issues/detail?id=69 :

- Simplify the switch statement code generation.
- Ensure that the switch value is always popped from the stack.

Credit goes to Feng for isolating the issue and proposing a fix.
Review URL: http://codereview.chromium.org/2888

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@315 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/codegen-arm.cc

@@ -2761,19 +2761,14 @@ void ArmCodeGenerator::VisitSwitchStatement(SwitchStatement* node) {
     Comment cmnt(masm_, "[ case clause");
 
     if (clause->is_default()) {
+      // Continue matching cases. The program will execute the default case's
+      // statements if it does not match any of the cases.
+      __ b(&next);
+      
       // Bind the default case label, so we can branch to it when we
       // have compared against all other cases.
       ASSERT(default_case.is_unused());  // at most one default clause
-
-      // If the default case is the first (but not only) case, we have
-      // to jump past it for now. Once we're done with the remaining
-      // clauses, we'll branch back here. If it isn't the first case,
-      // we jump past it by avoiding to chain it into the next chain.
-      if (length > 1) {
-        if (i == 0) __ b(&next);
-        __ bind(&default_case);
-      }
-
+      __ bind(&default_case);
     } else {
       __ bind(&next);
       next.Unuse();
@@ -2782,11 +2777,16 @@ void ArmCodeGenerator::VisitSwitchStatement(SwitchStatement* node) {
       Load(clause->label());
       Comparison(eq, true);
       Branch(false, &next);
-      // Entering the case statement -> remove the switch value from the stack
-      __ pop(r0);
     }
 
+    // Entering the case statement for the first time. Remove the switch value
+    // from the stack.
+    __ pop(r0);
+
     // Generate code for the body.
+    // This is also the target for the fall through from the previous case's
+    // statements which has to skip over the matching code and the popping of
+    // the switch value.
     __ bind(&fall_through);
     fall_through.Unuse();
     VisitStatements(clause->statements());
@@ -2794,11 +2794,15 @@ void ArmCodeGenerator::VisitSwitchStatement(SwitchStatement* node) {
   }
 
   __ bind(&next);
-  // Reached the end of the case statements -> remove the switch value
-  // from the stack.
-  __ pop(r0);  // __ Pop(no_reg)
-  if (default_case.is_bound()) __ b(&default_case);
-
+  // Reached the end of the case statements without matching any of the cases.
+  if (default_case.is_bound()) {
+    // A default case exists -> execute its statements.
+    __ b(&default_case);
+  } else {
+    // Remove the switch value from the stack.
+    __ pop(r0);
+  }
+  
   __ bind(&fall_through);
   __ bind(node->break_target());
 }

src/codegen-ia32.cc

@@ -2917,19 +2917,14 @@ void Ia32CodeGenerator::VisitSwitchStatement(SwitchStatement* node) {
     Comment cmnt(masm_, "[ case clause");
 
     if (clause->is_default()) {
+      // Continue matching cases. The program will execute the default case's
+      // statements if it does not match any of the cases.
+      __ jmp(&next);
+
       // Bind the default case label, so we can branch to it when we
       // have compared against all other cases.
       ASSERT(default_case.is_unused());  // at most one default clause
-
-      // If the default case is the first (but not only) case, we have
-      // to jump past it for now. Once we're done with the remaining
-      // clauses, we'll branch back here. If it isn't the first case,
-      // we jump past it by avoiding to chain it into the next chain.
-      if (length > 1) {
-        if (i == 0) __ jmp(&next);
-        __ bind(&default_case);
-      }
-
+      __ bind(&default_case);
     } else {
       __ bind(&next);
       next.Unuse();
@@ -2938,11 +2933,16 @@ void Ia32CodeGenerator::VisitSwitchStatement(SwitchStatement* node) {
       Load(clause->label());
       Comparison(equal, true);
       Branch(false, &next);
-      // Entering the case statement -> remove the switch value from the stack
-      __ pop(eax);
     }
 
+    // Entering the case statement for the first time. Remove the switch value
+    // from the stack.
+    __ pop(eax);
+
     // Generate code for the body.
+    // This is also the target for the fall through from the previous case's
+    // statements which has to skip over the matching code and the popping of
+    // the switch value.
     __ bind(&fall_through);
     fall_through.Unuse();
     VisitStatements(clause->statements());
@@ -2950,10 +2950,14 @@ void Ia32CodeGenerator::VisitSwitchStatement(SwitchStatement* node) {
   }
 
   __ bind(&next);
-  // Reached the end of the case statements -> remove the switch value
-  // from the stack
-  __ pop(eax);  // Pop(no_reg)
-  if (default_case.is_bound()) __ jmp(&default_case);
+  // Reached the end of the case statements without matching any of the cases.
+  if (default_case.is_bound()) {
+    // A default case exists -> execute its statements.
+    __ jmp(&default_case);
+  } else {
+    // Remove the switch value from the stack.
+    __ pop(eax);
+  }
 
   __ bind(&fall_through);
   __ bind(node->break_target());

test/mjsunit/regress/regress-69.js

@@ -0,0 +1,43 @@
+// Copyright 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
+//       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.
+
+// This tests a switch statement with only default clause leaves
+// balanced stack. It should not trigger the break point when --debug_code
+// flag is turned on.
+// See issue: http://code.google.com/p/v8/issues/detail?id=69
+
+// Flags: --debug-code --expose-gc
+function unbalanced_switch(a) {
+  try {
+    switch (a) {
+      default: break;
+    }
+  } catch (e) {}
+  gc();
+}
+
+unbalanced_switch(1);