[Vm-dev] Re: [Pharo-project] is there a way to avoid all the
#tryNamedPrimitive:with: * in ProtoObject
Eliot Miranda
eliot.miranda at gmail.com
Mon Jan 23 21:22:07 UTC 2012
On Mon, Jan 23, 2012 at 12:57 PM, Stéphane Ducasse <
stephane.ducasse at inria.fr> wrote:
> Hi elliot
>
> What are these tryNamedPrimitive?
>
The methods in ProtoObject implement invoking primitives in the context of
the debugger. The debugger used to use methods in Object, tryPrimitive0,
tryPrimitive1: tryPrimitive2:with: et al, to invoke normal primitives. The
debugger would choose the tryPrimitive1: method with the right number of
arguments, modify its header to change its primitive number of the desired
primitive, and then call it to invoke the primitive. This is not
reentrant. If one is trying to debug the debugger then the tryPrimitive:
method can be modified by the debugger that is debugging the debugger that
is in the process of editing the tryPrimitive: method. To fix this, and
eliminate the tryPrimitiveN methods, someone introduced the
tryPrimitive:withArgs: primitive. (Note that in VisualWorks we solved this
by creating a method on the fly to invoke a given primitive and evaluating
it using a primitive that did the same thing as withArgs:executeMethod:).
Analogously, one needs a way of invoking named primitives in the debugger,
and using tryNamedPrimitive[:with:with:...] et al has exactly the same
weaknesses as tryPrimitiveN above. So introducing a primitive to run named
primitives is in keeping with tryPrimitive:withArgs:. Using the
VisualWorks approach is feasible but violates Occam's razor.
Why do we need them in ProtoObject?
>
Once tryNamedPrimitiveIn:for:withArgs: is implemented in all relevant
virtual machines we don't need them. You'll notice that there is no trace
of the tryPrimitiveN methods anymore, even though they're in Smalltalk-80.
> Because I'm not sure that adding primitive to VM is always a good solution.
>
Agreed. But it is in keeping with the primitive for invoking numbered
primitives, tryPrimitive:withArgs:.
HTH
Eliot
> Stef
>
> > On Mon, Jan 23, 2012 at 8:52 AM, Mariano Martinez Peck <
> marianopeck at gmail.com> wrote:
> > Hi guys. I usually like to take a look to ProtoObject and see what is
> really needed for the minimal object. But having 30% of the methods being
> #tryNamedPrimitive:with: * is not fun.
> > So...I wonder, do you think there could be another way so that to avoid
> having all those methods in ProtoObject ?
> >
> > Yes there is. I implemented primitive 218 in Cog,
> primitiveDoNamedPrimitiveWithArgs, which is accessed via
> >
> >
> > tryNamedPrimitiveIn: aCompiledMethod for: aReceiver
> withArgs: arguments
> > | selector theMethod spec receiverClass |
> > <primitive: 218 error: ec>
> > ec ifNotNil:
> > ["If ec is an integer other than -1 there
> was a problem with primitive 218,
> > not with the external primitive itself.
> -1 indicates a generic failure (where
> > ec should be nil) but ec = nil means
> primitive 218 is not implemented. So
> > interpret -1 to mean the external
> primitive failed with a nil error code."
> > ec isInteger ifTrue:
> > [ec = -1
> > ifTrue: [ec := nil]
> > ifFalse: [self
> primitiveFailed]].
> > ^{PrimitiveFailToken. ec}].
> > "Assume a nil error code implies the primitive is
> not implemented and fall back on the old code."
> > "Hack. Attempt to execute the named primitive from
> the given compiled method"
> > arguments size > 8 ifTrue:
> > [^{PrimitiveFailToken. nil}].
> > selector := #(
> > tryNamedPrimitive
> > tryNamedPrimitive:
> > tryNamedPrimitive:with:
> > tryNamedPrimitive:with:with:
> > tryNamedPrimitive:with:with:with:
> > tryNamedPrimitive:with:with:with:with:
> > tryNamedPrimitive:with:with:with:with:with:
> >
> tryNamedPrimitive:with:with:with:with:with:with:
> >
> tryNamedPrimitive:with:with:with:with:with:with:with:) at: arguments size+1.
> > receiverClass := self objectClass: aReceiver.
> > theMethod := receiverClass lookupSelector:
> selector.
> > theMethod == nil ifTrue:
> > [^{PrimitiveFailToken. nil}].
> > spec := theMethod literalAt: 1.
> > spec replaceFrom: 1 to: spec size with:
> (aCompiledMethod literalAt: 1) startingAt: 1.
> > Smalltalk unbindExternalPrimitives.
> > ^self object: aReceiver perform: selector
> withArguments: arguments inClass: receiverClass
> >
> > (cf tryPrimitive: withArgs:) and used in
> >
> >
> > doPrimitive: primitiveIndex method: meth receiver:
> receiver args: arguments
> > "Simulate a primitive method whose index is
> primitiveIndex. The simulated receiver
> > and arguments are given as arguments to this
> message. Any primitive which provokes
> > execution needs to be intercepted and simulated
> to avoid execution running away."
> >
> > | value |
> > "If successful, push result and return resuming
> context, else ^ { PrimitiveFailToken. errorCode }"
> > (primitiveIndex = 19) ifTrue:
> > [ToolSet
> > debugContext: self
> > label:'Code simulation error'
> > contents: nil].
> >
> > "ContextPart>>blockCopy:; simulated to get startpc
> right"
> > (primitiveIndex = 80 and: [(self objectClass:
> receiver) includesBehavior: ContextPart])
> > ifTrue: [^self push: ((BlockContext
> newForMethod: receiver method)
> > home:
> receiver home
> > startpc:
> pc + 2
> > nargs:
> (arguments at: 1))].
> > (primitiveIndex = 81 and: [(self objectClass:
> receiver) == BlockContext]) "BlockContext>>value[:value:...]"
> > ifTrue: [^receiver pushArgs: arguments
> from: self].
> > (primitiveIndex = 82 and: [(self objectClass:
> receiver) == BlockContext]) "BlockContext>>valueWithArguments:"
> > ifTrue: [^receiver pushArgs: arguments
> first from: self].
> > primitiveIndex = 83 "afr 9/11/1998 19:50"
> "Object>>perform:[with:...]"
> > ifTrue: [^self send: arguments first
> > to: receiver
> > with: arguments
> allButFirst
> > super: false].
> > primitiveIndex = 84 "afr 9/11/1998 19:50 & eem
> 8/18/2009 17:04" "Object>>perform:withArguments:"
> > ifTrue: [^self send: arguments first
> > to: receiver
> > with: (arguments
> at: 2)
> > startClass: nil].
> > primitiveIndex = 100 "eem 8/18/2009 16:57"
> "Object>>perform:withArguments:inSuperclass:"
> > ifTrue: [^self send: arguments first
> > to: receiver
> > with: (arguments
> at: 2)
> > startClass:
> (arguments at: 3)].
> >
> > "Mutex>>primitiveEnterCriticalSection
> >
> Mutex>>primitiveTestAndSetOwnershipOfCriticalSection"
> > (primitiveIndex = 186 or: [primitiveIndex = 187])
> ifTrue:
> > [| active effective |
> > active := Processor activeProcess.
> > effective := active effectiveProcess.
> > "active == effective"
> > value := primitiveIndex = 186
> > ifTrue: [receiver
> primitiveEnterCriticalSectionOnBehalfOf: effective]
> > ifFalse: [receiver
> primitiveTestAndSetOwnershipOfCriticalSectionOnBehalfOf: effective].
> > ^(value isArray
> > and: [value size = 2
> > and: [value first ==
> PrimitiveFailToken]])
> > ifTrue: [value]
> > ifFalse: [self push: value]].
> >
> > primitiveIndex = 188 ifTrue: "eem 5/27/2008 11:10
> Object>>withArgs:executeMethod:"
> > [^MethodContext
> > sender: self
> > receiver: receiver
> > method: (arguments at: 2)
> > arguments: (arguments at: 1)].
> >
> > "Closure primitives"
> > (primitiveIndex = 200 and: [self == receiver])
> ifTrue:
> > "ContextPart>>closureCopy:copiedValues:;
> simulated to get startpc right"
> > [^self push: (BlockClosure
> >
> outerContext: receiver
> > startpc:
> pc + 2
> > numArgs:
> arguments first
> >
> copiedValues: arguments last)].
> > ((primitiveIndex between: 201 and: 205)
> "BlockClosure>>value[:value:...]"
> > or: [primitiveIndex between: 221 and: 222])
> ifTrue: "BlockClosure>>valueNoContextSwitch[:]"
> > [^receiver simulateValueWithArguments:
> arguments caller: self].
> > primitiveIndex = 206 ifTrue:
> "BlockClosure>>valueWithArguments:"
> > [^receiver simulateValueWithArguments:
> arguments first caller: self].
> >
> > primitiveIndex = 118 ifTrue:
> "tryPrimitive:withArgs:; avoid recursing in the VM"
> > [(arguments size = 2
> > and: [arguments first isInteger
> > and: [arguments last class == Array]])
> ifFalse:
> > [^ContextPart
> primitiveFailTokenFor: nil].
> > ^self doPrimitive: arguments first
> method: meth receiver: receiver args: arguments last].
> >
> > value := primitiveIndex = 120 "FFI method"
> > ifTrue: [(meth literalAt:
> 1) tryInvokeWithArguments: arguments]
> > ifFalse:
> > [primitiveIndex =
> 117 "named primitives"
> > ifTrue:
> [self tryNamedPrimitiveIn: meth for: receiver withArgs: arguments]
> > ifFalse:
> >
> [receiver tryPrimitive: primitiveIndex withArgs: arguments]].
> > ^(value isArray
> > and: [value size = 2
> > and: [value first == PrimitiveFailToken]])
> > ifTrue: [value]
> > ifFalse: [self push: value]
> >
> > (find attached). But these need implementing in the standard VM before
> they can be used in Pharo, Squeak, etc.
> >
> >
> > Thanks
> >
> > --
> > Mariano
> > http://marianopeck.wordpress.com
> >
> >
> >
> >
> > --
> > best,
> > Eliot
> >
>
>
>
--
best,
Eliot
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.squeakfoundation.org/pipermail/vm-dev/attachments/20120123/0d795ba3/attachment-0001.htm
More information about the Vm-dev
mailing list