Changeset 36976 in webkit for trunk/JavaScriptCore/kjs/JSNumberCell.h

Timestamp:

Sep 26, 2008, 6:44:15 PM (17 years ago)

Author:

[email protected]

Message:

2008-09-26 Gavin Barraclough <​[email protected]>

Reviewed by Maciej Stachowiak & Oliver Hunt.

Add support for reusing temporary JSNumberCells. This change is based on the observation
that if the result of certain operations is a JSNumberCell and is consumed by a subsequent
operation that would produce a JSNumberCell, we can reuse the object rather than allocating
a fresh one. E.g. given the expression ((a * b) * c), we can statically determine that
(a * b) will have a numeric result (or else it will have thrown an exception), so the result
will either be a JSNumberCell or a JSImmediate.

This patch changes three areas of JSC:

• The AST now tracks type information about the result of each node.
• This information is consumed in bytecode compilation, and certain bytecode operations now carry the statically determined type information about their operands.
• CTI uses the information in a number of fashions:
  • Where an operand to certain arithmetic operations is reusable, it will plant code to try to perform the operation in JIT code & reuse the cell, where appropriate.
  • Where it can be statically determined that an operand can only be numeric (typically the result of another arithmetic operation) the code will not redundantly check that the JSCell is a JSNumberCell.
  • Where either of the operands to an add are non-numeric do not plant an optimized arithmetic code path, just call straight out to the C function.

+6% Sunspider (10% progression on 3D, 16% progression on math, 60% progression on access-nbody),
+1% v8-tests (improvements in raytrace & crypto)

• VM/CTI.cpp: Add optimized code generation with reuse of temporary JSNumberCells.
• VM/CTI.h:
• kjs/JSNumberCell.h:
• masm/X86Assembler.h:

• VM/CodeBlock.cpp: Add type information to specific bytecodes.
• VM/CodeGenerator.cpp:
• VM/CodeGenerator.h:
• VM/Machine.cpp:

• kjs/nodes.cpp: Track static type information for nodes.
• kjs/nodes.h:
• kjs/ResultDescriptor.h: (Added)
• JavaScriptCore.xcodeproj/project.pbxproj:

File:

• trunk/JavaScriptCore/kjs/JSNumberCell.h (modified) (1 diff)

trunk/JavaScriptCore/kjs/JSNumberCell.h

@@ -43 +43 @@
 
     class JSNumberCell : public JSCell {
+        friend class CTI;
         friend JSValue* jsNumberCell(ExecState*, double);
         friend JSValue* jsNaN(ExecState*);