As profiler data show, the execution time of the nextNode and replaceCurrent
methods in PreorderNodeIterator contribute quite significantly to the total
time to run Context.compileReader.
replaceCurrent is slow because it calls Node.replaceChild which have to
iterate through all previous siblings to find the nearest to the current.
But it is easy to avoid this search by caching the previous sibling of the
current while iterating over the node tree in nextNode.
nextNode slowness is attributed to the usage of java.lang.Stack which is
expensive due to its synchronized methods. In the attched patch I replaced
it by the explicit array management.
It allows to cut Context.compileReader time by 5%-30% when processing
20K-3MB sources assembled form JS files in the test suite.
Note form omj/Parser.java:
* OPT source info collection is a potential performance bottleneck;
* Source wraps a java.lang.StringBuffer, which is synchronized. It
* might be faster to implement Source with its own char buffer and
* toString method.
It is indeed a bottleneck under JDK 1.1. When I replaced StringBuffer
by a char array (see the attached patch), execution time of
Context.compileReader decreased by 15%: to test I combined a few test
cases to get a 3MB JS source and then measured time to process it by
Context.compileReader in the interpreter mode.
Under JDK 1.3 the difference is less then 1%, but still using the explicit
string buffer saves memory. When converting StringBuffer to String Sun JDK
shares the internal char array in StringBuffer with new String, but in the
Parser case typically the capacity of this buffer is bigger then the actual
string length, so this unused space in source strings is wasted in the
interpreter mode that keeps these strings in InterpreterData.
Regards, Igor
========
I implemented that member expression as function name syntactic sugar to
support scripts using this MS extension. This is only available when
Context.hasFeature(Context.FEATURE_MEMBER_EXPR_AS_FUNCTION_NAME)
returns true to allow the deviation from the standard only when required.
The patch effectively transforms 'function <memberExpr>(...)...' to
'<memberExpr> = function(...)...' when <memberExpr> is not simple
identifier. I am not sure that MS implementation does exactly this
but hopefully it is sufficiently general to cover MS cases.
(The patch assumes that source_change.patch is already applied)
Regards, Igor
I implemented that member expression as function name syntactic sugar to support
scripts using this MS extension. This is only available when
Context.hasFeature(Context.FEATURE_MEMBER_EXPR_AS_FUNCTION_NAME)
returns true to allow the deviation from the standard only when required.
The patch effectively transforms 'function <memberExpr>(...)...' to
'<memberExpr> = function(...)...' when <memberExpr> is not simple identifier.
I am not sure that MS implementation does exactly this but hopefully it is
sufficiently general to cover MS cases.
(The patch assumes that source_change.patch is already applied)
Regards, Igor
Currently omj/TokenStream and omj/optimizer/Optimizer.java both contain
code to convert number value to a wrapper object of smallest size. The
attached patch moves this wrapping to Node constructor to avoid code
duplication and eliminate special treatment of exact integers in
Optimizer.java.
The constant folding code in omj/optimizer/Optimizer.java currently always
replaces x * 1, x - 0 by simply x which does not force the toNumber convertion,
which is visible, for example, via typeof. For example, when running at
optimization level 2, the following
function f() {
return "0" * 1;
}
print(typeof(f()));
prints "string" instead of expected "number".
The const_fold.patch fixes this via replacing x*1 by (+x) to force number convertion.
It assumes that the patch with number wrapping changes is in place.
convert number value to a wrapper object of smallest size. The attached patch
moves this wrapping to Node constructor to avoid code duplication and eliminate
special treatment of exact integers in Optimizer.java.
Currently omj/optimizer/Codegen.java uses special classes ConstantList
and ConstantDude to store the list of static constants in the generated
class. It seems that using a simple double[] array with a constant
counter and checking via "(int)number == number" for constant types not
only eliminates these 2 classes but makes the whole code simple, see
the attached patch.
The patch also modifies nodeIsConvertToObjectOfNumber to return not a
Number, but the number node itself that is used to extract double
value directly via Node.getDouble() call. I changed it to allow to
store values of number literals in nodes without using wrapper object.
Replacing usage of ShallowNodeIterator to loop throw node children by
explicit calls to Node.getFirstChild()/ Node.getNextSibling()) with
comments when the node children list is modified while iterating
through it.
It avoids creation of ShallowNodeIterator objects and eliminates the
need to have ShallowNodeIterator class.
Currently Rhino source has quite a few places with code like (String)node.getDatum()
or ((Number)node.getDatum()).doubleValue(). The patch changes this usage to call
node.getString() or node.getDouble().
It also adds new constructors to Node to accept int or double values in addition to
Object datum to replace new Node(token, new Integer(x)) by Node(token, x) etc. It
may allow in future not to create a wrapper object for int or double datum to speed
up parsing.
