>
> On Sun, May 22, 2011 at 8:54 AM, David T. Lewis <
lewis@mail.msen.com> wrote:
>
> >
> > I have been trying to gradually update trunk VMMaker to better align
> > with oscog VMMaker (an admittedly slow process, but hopefully still
> > worthwhile). I have gotten the interpreter primitives moved into class
> > InterpreterPrimitives and verified no changes to generated code. This
> > greatly reduces the clutter in class Interpreter, so it's a nice change
> > I think.
> >
> > My next step was to update all of the primitives to use the
> > #primitiveFailFor:
> > idiom, in which the successFlag variable is replaced with primFailCode
> > (integer value, 0 for success, 1, 2, 3... for failure codes). This would
> > get us closer to the point where the standard interpreter and stack/cog
> > would use a common set of primitives. A lot of changes were required for
> > this, but the resulting VM works fine ... except for performance.
> >
> > On a standard interpreter, use of primFailCode seems to result in a
> > nearly 12% reduction in bytecode performance as measured by tinyBenchmarks:
> >
> > Standard interpreter (using successFlag):
> > 0 tinyBenchmarks. '439108061 bytecodes/sec; 15264622 sends/sec'
> > 0 tinyBenchmarks. '433164128 bytecodes/sec; 14740358 sends/sec'
> > 0 tinyBenchmarks. '445993031 bytecodes/sec; 15040691 sends/sec'
> > 0 tinyBenchmarks. '440999138 bytecodes/sec; 15052960 sends/sec'
> > 0 tinyBenchmarks. '445993031 bytecodes/sec; 14485815 sends/sec'
> >
> > After updating the standard interpreter (using primFailCode):
> > 0 tinyBenchmarks. '393241167 bytecodes/sec; 14066256 sends/sec'
> > 0 tinyBenchmarks. '392036753 bytecodes/sec; 15040691 sends/sec'
> > 0 tinyBenchmarks. '393846153 bytecodes/sec; 14272953 sends/sec'
> > 0 tinyBenchmarks. '400625978 bytecodes/sec; 14991818 sends/sec'
> > 0 tinyBenchmarks. '393846153 bytecodes/sec; 15176750 sends/sec'
> >
> > This is a much larger performance difference than I expected to see.
> > Actually I expected no measurable difference at all, and I was just
> > testing to verify this. But 12% is a lot, so I want to ask if I'm
> > missing something?
> >
> > The changes to generated code generally take the form of:
> >
> > Testing success status, original:
> > if (successFlag) { ... }
> >
> > Testing success status, new:
> > if (foo->primFailCode == 0) { ... }
> >
> > Setting failure status, original:
> > successFlag = 0;
> >
> > Setting failure status, new:
> > if (foo->primFailCode == 0) {
> > foo->primFailCode = 1;
> > }
> >
> > My approach to doing the updates was as follows:
> > - Replace all occurrences of "successFlag := true" with "self
> > initPrimCall",
> > which initialize primFailCode to 0.
> > - Replace all "successFlag := false" with "self primitiveFail".
> > - Replace all "successFlag ifTrue: [] ifFalse: []" with
> > "self successful ifTrue: [] ifFalse: []".
> > - Update #primitiveFail, #failed and #success: to use primFailCode rather
> > than successFlag.
> > - Remove successFlag variable.
> >
> > Obviously I don't want to publish the code on SqS/VMMaker, but I can mail
> > an interp.c if anyone wants to see the gory details (It is too large to
> > post on this mailing list though).
> >
> > Any advice appreciated. I suspect I'm missing something basic here.
> >
> > Thanks,
> > Dave
> >
> >