Title: [200898] trunk/Source/_javascript_Core
Revision
200898
Author
[email protected]
Date
2016-05-13 16:45:44 -0700 (Fri, 13 May 2016)

Log Message

[JSC] SetLocal without exit do not need phantoms
https://bugs.webkit.org/show_bug.cgi?id=157653

Patch by Benjamin Poulain <[email protected]> on 2016-05-13
Reviewed by Filip Pizlo.

I made a mistake in r200498.

If a SetLocal cannot possibly exit, we were not clearing
the source of the operand. As a result, we sometime kept
a value alive up to the end of the block.

That's uncommon because SetLocal typically appear
toward the end of blocks. That's probably why there was
no perf impact with that fix.

* dfg/DFGPhantomInsertionPhase.cpp:

Modified Paths

Diff

Modified: trunk/Source/_javascript_Core/ChangeLog (200897 => 200898)


--- trunk/Source/_javascript_Core/ChangeLog	2016-05-13 23:45:15 UTC (rev 200897)
+++ trunk/Source/_javascript_Core/ChangeLog	2016-05-13 23:45:44 UTC (rev 200898)
@@ -1,5 +1,24 @@
 2016-05-13  Benjamin Poulain  <[email protected]>
 
+        [JSC] SetLocal without exit do not need phantoms
+        https://bugs.webkit.org/show_bug.cgi?id=157653
+
+        Reviewed by Filip Pizlo.
+
+        I made a mistake in r200498.
+
+        If a SetLocal cannot possibly exit, we were not clearing
+        the source of the operand. As a result, we sometime kept
+        a value alive up to the end of the block.
+
+        That's uncommon because SetLocal typically appear
+        toward the end of blocks. That's probably why there was
+        no perf impact with that fix.
+
+        * dfg/DFGPhantomInsertionPhase.cpp:
+
+2016-05-13  Benjamin Poulain  <[email protected]>
+
         [JSC] Move the CheckTierUp function calls out of the main path
         https://bugs.webkit.org/show_bug.cgi?id=157668
 

Modified: trunk/Source/_javascript_Core/dfg/DFGPhantomInsertionPhase.cpp (200897 => 200898)


--- trunk/Source/_javascript_Core/dfg/DFGPhantomInsertionPhase.cpp	2016-05-13 23:45:15 UTC (rev 200897)
+++ trunk/Source/_javascript_Core/dfg/DFGPhantomInsertionPhase.cpp	2016-05-13 23:45:44 UTC (rev 200898)
@@ -173,12 +173,14 @@
                     killedNode->defaultEdge());
             };
 
-            if (nodeMayExit && node->op() == SetLocal) {
-                // If the SetLocal does exit, we need the MovHint of its local
-                // to be live until the SetLocal is done.
+            if (node->op() == SetLocal) {
                 VirtualRegister local = node->local();
-                processKilledOperand(local);
-                alreadyKilled = local;
+                if (nodeMayExit) {
+                    // If the SetLocal does exit, we need the MovHint of its local
+                    // to be live until the SetLocal is done.
+                    processKilledOperand(local);
+                    alreadyKilled = local;
+                }
                 m_values.operand(local) = nullptr;
             }
 
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