Changeset 180656 in webkit for trunk/Source/JavaScriptCore/dfg/DFGClobberize.cpp

Timestamp:

Feb 25, 2015, 8:29:26 PM (10 years ago)

Author:

[email protected]

Message:

DFG abstract heaps should respect the difference between heap and stack
​https://bugs.webkit.org/show_bug.cgi?id=142022

Reviewed by Geoffrey Garen.

We will soon (​https://bugs.webkit.org/show_bug.cgi?id=141174) be in a world where a "world
clobbering" operation cannot write to our stack, but may be able to read from it. This
means that we need to change the DFG abstract heap hierarchy to have a notion of Heap that
subsumes all that World previously subsumed, and a new notion of Stack that is a subtype
of World and a sibling of Heap.

So, henceforth "clobbering the world" means reading World and writing Heap.

This makes a bunch of changes to make this work, including changing the implementation of
disjointness in AbstractHeap to make it support a more general hierarchy. I was expecting
a slow-down, but I measured the heck out of this and found no perf difference.

• dfg/DFGAbstractHeap.cpp:

(JSC::DFG::AbstractHeap::dump):

• dfg/DFGAbstractHeap.h:

(JSC::DFG::AbstractHeap::supertype):
(JSC::DFG::AbstractHeap::isStrictSubtypeOf):
(JSC::DFG::AbstractHeap::isSubtypeOf):
(JSC::DFG::AbstractHeap::overlaps):
(JSC::DFG::AbstractHeap::isDisjoint):

• dfg/DFGClobberize.cpp:

(JSC::DFG::clobbersHeap):
(JSC::DFG::clobbersWorld): Deleted.

• dfg/DFGClobberize.h:

(JSC::DFG::clobberize):

• dfg/DFGDoesGC.cpp:

(JSC::DFG::doesGC):

File:

• trunk/Source/JavaScriptCore/dfg/DFGClobberize.cpp (modified) (2 diffs)

trunk/Source/JavaScriptCore/dfg/DFGClobberize.cpp

@@ -57 +57 @@
 }
 
-bool clobbersWorld(Graph& graph, Node* node)
+bool clobbersHeap(Graph& graph, Node* node)
 {
     bool result = false;
@@ -63 +63 @@
         graph, node, NoOpClobberize(),
         [&] (AbstractHeap heap) {
-            if (heap == AbstractHeap(World))
+            switch (heap.kind()) {
+            case World:
+            case Heap:
                 result = true;
+                break;
+            default:
+                break;
+            }
         },
         NoOpClobberize());