Changeset 197155 in webkit

Timestamp:

Feb 25, 2016, 6:04:42 PM (11 years ago)

Author:

benjamin@webkit.org

Message:

[JSC] Temporal Dead Zone checks on "this" are eliminated when doing OSR Entry to FTL
​https://bugs.webkit.org/show_bug.cgi?id=154664

Reviewed by Saam Barati.

When doing OSR Enter into a constructor, we lose the information
that this may have been set to empty by a previously executed block.

All the code just assumed the type for a FlushedJS value and thus
not an empty value. It was then okay to eliminate the TDZ checks.

In this patch, the values on root entry now assume they may be empty.
As a result, the SetArgument() for "this" has "empty" as possible
type and the TDZ checks are no longer eliminated.

• dfg/DFGInPlaceAbstractState.cpp:

(JSC::DFG::InPlaceAbstractState::initialize):

Location:

trunk/Source/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• dfg/DFGInPlaceAbstractState.cpp (modified) (1 diff)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2016-02-25  Benjamin Poulain  <benjamin@webkit.org>
+
+        [JSC] Temporal Dead Zone checks on "this" are eliminated when doing OSR Entry to FTL
+        https://bugs.webkit.org/show_bug.cgi?id=154664
+
+        Reviewed by Saam Barati.
+
+        When doing OSR Enter into a constructor, we lose the information
+        that this may have been set to empty by a previously executed block.
+
+        All the code just assumed the type for a FlushedJS value and thus
+        not an empty value. It was then okay to eliminate the TDZ checks.
+
+        In this patch, the values on root entry now assume they may be empty.
+        As a result, the SetArgument() for "this" has "empty" as possible
+        type and the TDZ checks are no longer eliminated.
+
+        * dfg/DFGInPlaceAbstractState.cpp:
+        (JSC::DFG::InPlaceAbstractState::initialize):
+
 2016-02-25  Ada Chan  <adachan@apple.com>
 

trunk/Source/JavaScriptCore/dfg/DFGInPlaceAbstractState.cpp

@@ -122 +122 @@
             break;
         case FlushedJSValue:
-            root->valuesAtHead.argument(i).makeHeapTop();
+            root->valuesAtHead.argument(i).makeBytecodeTop();
             break;
         default: