Changeset 34852 in webkit for trunk/JavaScriptCore/VM/CodeGenerator.h

Timestamp:

Jun 28, 2008, 9:03:11 AM (17 years ago)

Author:

Darin Adler

Message:

2008-06-28 Darin Adler <Darin Adler>

Reviewed by Oliver.

• fix ​https://bugs.webkit.org/show_bug.cgi?id=19796 optimize expressions with ignored results (especially post-increment)

SunSpider says 0.9% faster.

• VM/CodeGenerator.h: (KJS::CodeGenerator::tempDestination): Create a new temporary for ignoredResult() too, just as we would for 0. (KJS::CodeGenerator::finalDestination): Use the temporary if the register passed in is ignoredResult() too, just as we would for 0. (KJS::CodeGenerator::destinationForAssignResult): Return 0 if the passed in register is ignoredResult(), just as we would for 0. (KJS::CodeGenerator::moveToDestinationIfNeeded): Return 0 if the register passed in is ignoredResult(). What matters is that we don't want to emit a move. The return value won't be looked at. (KJS::CodeGenerator::emitNode): Allow ignoredResult() and pass it through to the node's emitCode function.

• VM/RegisterID.h: (KJS::ignoredResult): Added. Special value to indicate the result of a node will be ignored and need not be put in any register.

• kjs/nodes.cpp: (KJS::NullNode::emitCode): Do nothing if dst == ignoredResult(). (KJS::BooleanNode::emitCode): Ditto. (KJS::NumberNode::emitCode): Ditto. (KJS::StringNode::emitCode): Ditto. (KJS::RegExpNode::emitCode): Ditto. (KJS::ThisNode::emitCode): Ditto. (KJS::ResolveNode::emitCode): Do nothing if dst == ignoredResult() and the identifier resolves to a local variable. (KJS::ObjectLiteralNode::emitCode): Do nothing if dst == ignoredResult() and the object is empty. (KJS::PostIncResolveNode::emitCode): If dst == ignoredResult(), then do nothing for the local constant case, and do a pre-increment in all the other cases. (KJS::PostDecResolveNode::emitCode): Ditto. (KJS::PostIncBracketNode::emitCode): Ditto. (KJS::PostDecBracketNode::emitCode): Ditto. (KJS::PostIncDotNode::emitCode): Ditto. (KJS::PostDecDotNode::emitCode): Ditto. (KJS::DeleteValueNode::emitCode): Pass ignoredResult() when evaluating the expression. (KJS::VoidNode::emitCode): Ditto. (KJS::TypeOfResolveNode::emitCode): If dst == ignoredResult(), do nothing if the identifier resolves to a local variable, and don't bother generating a typeof opcode in the other case. (KJS::TypeOfValueNode::emitCode): Ditto. (KJS::PreIncResolveNode::emitCode): Do nothing if dst == ignoredResult() and the identifier resolves to a local constant. (KJS::PreDecResolveNode::emitCode): Ditto. (KJS::AssignResolveNode::emitCode): Turn ignoredResult() into 0 in a couple places, because we need to put the result into a register so we can assign it. At other sites this is taken care of by functions like finalDestination. (KJS::CommaNode::emitCode): Pass ignoredResult() when evaluating the first expression. (KJS::ForNode::emitCode): Pass ignoredResult() when evaluating the first and third expressions. (KJS::ForInNode::emitCode): Pass ignoredResult() when evaluating the first expression.

File:

• trunk/JavaScriptCore/VM/CodeGenerator.h (modified) (2 diffs)

trunk/JavaScriptCore/VM/CodeGenerator.h

@@ -129 +129 @@
         // Functions for handling of dst register
 
-        // Returns  a place to write intermediate values of an operation
+        // Returns a place to write intermediate values of an operation
         // which reuses dst if it is safe to do so.
-
-        RegisterID* tempDestination(RegisterID* dst) { return (dst && dst->isTemporary()) ? dst : newTemporary(); }
+        RegisterID* tempDestination(RegisterID* dst)
+        {
+            return (dst && dst != ignoredResult() && dst->isTemporary()) ? dst : newTemporary();
+        }
 
         // Returns the place to write the final output of an operation.
         RegisterID* finalDestination(RegisterID* originalDst, RegisterID* tempDst = 0)
         {
-            if (originalDst)
+            if (originalDst && originalDst != ignoredResult())
                 return originalDst;
+            ASSERT(tempDst != ignoredResult());
             if (tempDst && tempDst->isTemporary())
                 return tempDst;
@@ -146 +149 @@
         RegisterID* destinationForAssignResult(RegisterID* dst)
         {
-            if (dst && m_codeBlock->needsFullScopeChain)
+            if (dst && dst != ignoredResult() && m_codeBlock->needsFullScopeChain)
                 return dst->isTemporary() ? dst : newTemporary();
             return 0;
         }
 
-        // moves src to dst if dst is not null and is different from src, otherwise just returns src
-        RegisterID* moveToDestinationIfNeeded(RegisterID* dst, RegisterID* src) { return (dst && dst != src) ? emitMove(dst, src) : src; }
+        // Moves src to dst if dst is not null and is different from src, otherwise just returns src.
+        RegisterID* moveToDestinationIfNeeded(RegisterID* dst, RegisterID* src)
+        {
+            return dst == ignoredResult() ? 0 : (dst && dst != src) ? emitMove(dst, src) : src;
+        }
 
         PassRefPtr<LabelID> newLabel();
 
         // The emitNode functions are just syntactic sugar for calling
-        // Node::emitCode. They're the only functions that accept a NULL register.
+        // Node::emitCode. These functions accept a 0 for the register,
+        // meaning that the node should allocate a register, or ignoredResult(),
+        // meaning that the node need not put the result in a register.
+        // Other emit functions do not accept 0 or ignoredResult().
         RegisterID* emitNode(RegisterID* dst, Node* n)
         {
             // Node::emitCode assumes that dst, if provided, is either a local or a referenced temporary.
-            ASSERT(!dst || !dst->isTemporary() || dst->refCount());
+            ASSERT(!dst || dst == ignoredResult() || !dst->isTemporary() || dst->refCount());
             if (!m_codeBlock->lineInfo.size() || m_codeBlock->lineInfo.last().lineNumber != n->lineNo()) {
                 LineInfo info = { instructions().size(), n->lineNo() };