Changeset 141222 in webkit

Timestamp:

Jan 29, 2013 9:43:47 PM (11 years ago)

Author:

ggaren@apple.com

Message:

Be a little more conservative about emitting table-based switches
​https://bugs.webkit.org/show_bug.cgi?id=108292

Reviewed by Filip Pizlo.

Profiling shows we're using op_switch in cases where it's a regression.

• bytecompiler/NodesCodegen.cpp:

(JSC):
(JSC::length):
(JSC::CaseBlockNode::tryTableSwitch):
(JSC::CaseBlockNode::emitBytecodeForBlock):

• parser/Nodes.h:

(CaseBlockNode):

Location:

trunk/Source/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• bytecompiler/NodesCodegen.cpp (modified) (2 diffs)
• parser/Nodes.h (modified) (1 diff)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2013-01-29  Geoffrey Garen  <ggaren@apple.com>
+
+        Be a little more conservative about emitting table-based switches
+        https://bugs.webkit.org/show_bug.cgi?id=108292
+
+        Reviewed by Filip Pizlo.
+
+        Profiling shows we're using op_switch in cases where it's a regression.
+
+        * bytecompiler/NodesCodegen.cpp:
+        (JSC):
+        (JSC::length):
+        (JSC::CaseBlockNode::tryTableSwitch):
+        (JSC::CaseBlockNode::emitBytecodeForBlock):
+        * parser/Nodes.h:
+        (CaseBlockNode):
+
 2013-01-29  Sheriff Bot  <webkit.review.bot@gmail.com>
 

trunk/Source/JavaScriptCore/bytecompiler/NodesCodegen.cpp

@@ -1852 +1852 @@
     }
 }
-    
-SwitchInfo::SwitchType CaseBlockNode::tryOptimizedSwitch(Vector<ExpressionNode*, 8>& literalVector, int32_t& min_num, int32_t& max_num)
-{
+
+static inline size_t length(ClauseListNode* list1, ClauseListNode* list2)
+{
+    size_t length = 0;
+    for (ClauseListNode* node = list1; node; node = node->getNext())
+        ++length;
+    for (ClauseListNode* node = list2; node; node = node->getNext())
+        ++length;
+    return length;
+}
+
+SwitchInfo::SwitchType CaseBlockNode::tryTableSwitch(Vector<ExpressionNode*, 8>& literalVector, int32_t& min_num, int32_t& max_num)
+{
+    if (length(m_list1, m_list2) < s_tableSwitchMinimum)
+        return SwitchInfo::SwitchNone;
+
     SwitchKind typeForTable = SwitchUnset;
     bool singleCharacterSwitch = true;
@@ -1889 +1902 @@
     int32_t min_num = std::numeric_limits<int32_t>::max();
     int32_t max_num = std::numeric_limits<int32_t>::min();
-    SwitchInfo::SwitchType switchType = tryOptimizedSwitch(literalVector, min_num, max_num);
+    SwitchInfo::SwitchType switchType = tryTableSwitch(literalVector, min_num, max_num);
 
     if (switchType != SwitchInfo::SwitchNone) {

trunk/Source/JavaScriptCore/parser/Nodes.h

@@ -1510 +1510 @@
 
     private:
-        SwitchInfo::SwitchType tryOptimizedSwitch(Vector<ExpressionNode*, 8>& literalVector, int32_t& min_num, int32_t& max_num);
+        SwitchInfo::SwitchType tryTableSwitch(Vector<ExpressionNode*, 8>& literalVector, int32_t& min_num, int32_t& max_num);
+        static const size_t s_tableSwitchMinimum = 10;
         ClauseListNode* m_list1;
         CaseClauseNode* m_defaultClause;