Changeset 249052 in webkit

Timestamp:

Aug 23, 2019 10:21:19 AM (5 years ago)

Author:

mark.lam@apple.com

Message:

VirtualRegister::dump() can use more informative CallFrame header slot names.
​https://bugs.webkit.org/show_bug.cgi?id=201062

Reviewed by Tadeu Zagallo.

For example, it currently dumps head3 instead of callee. This patch changes the
dump as follows (for 64-bit addressing):

head0 => callerFrame
head1 => returnPC
head2 => codeBlock
head3 => callee
head4 => argumentCount

Now, one might be wondering when would bytecode ever access callerFrame and
returnPC? The answer is never. However, I don't think its the role of the
dumper to catch a bug where these header slots are being used. The dumper's role
is to clearly report them so that we can see that these unexpected values are
being used.

• bytecode/VirtualRegister.cpp:

(JSC::VirtualRegister::dump const):

Location:

trunk/Source/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• bytecode/VirtualRegister.cpp (modified) (2 diffs)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2019-08-22  Mark Lam  <mark.lam@apple.com>
+
+        VirtualRegister::dump() can use more informative CallFrame header slot names.
+        https://bugs.webkit.org/show_bug.cgi?id=201062
+
+        Reviewed by Tadeu Zagallo.
+
+        For example, it currently dumps head3 instead of callee.  This patch changes the
+        dump as follows (for 64-bit addressing):
+            head0 => callerFrame
+            head1 => returnPC
+            head2 => codeBlock
+            head3 => callee
+            head4 => argumentCount
+
+        Now, one might be wondering when would bytecode ever access callerFrame and
+        returnPC?  The answer is never.  However, I don't think its the role of the
+        dumper to catch a bug where these header slots are being used.  The dumper's role
+        is to clearly report them so that we can see that these unexpected values are
+        being used.
+
+        * bytecode/VirtualRegister.cpp:
+        (JSC::VirtualRegister::dump const):
+
 2019-08-22  Andy Estes  <aestes@apple.com>
 

trunk/Source/JavaScriptCore/bytecode/VirtualRegister.cpp

@@ -1 +1 @@
 /*
- * Copyright (C) 2011, 2015 Apple Inc. All rights reserved.
+ * Copyright (C) 2011-2019 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -39 +39 @@
     
     if (isHeader()) {
-        out.print("head", m_virtualRegister);
+        if (m_virtualRegister == CallFrameSlot::codeBlock)
+            out.print("codeBlock");
+        else if (m_virtualRegister == CallFrameSlot::callee)
+            out.print("callee");
+        else if (m_virtualRegister == CallFrameSlot::argumentCount)
+            out.print("argumentCount");
+#if CPU(ADDRESS64)
+        else if (!m_virtualRegister)
+            out.print("callerFrame");
+        else if (m_virtualRegister == 1)
+            out.print("returnPC");
+#else
+        else if (!m_virtualRegister)
+            out.print("callerFrameAndReturnPC");
+#endif
         return;
     }