VM Maker: VMMaker-dtl.350.mcz

I know that "unsigned" means "unsigned int". That is the intent.

With the primitive as currently implemented, that variable must be 32
bits, otherwise the shift left can successfully produce a five byte large
integer that is truncated to four without failing the primitive. This
change is to fix the current implementation of the primitive in the case
of sizeof(sqInt) == 8.

Dave

>  Hi David,
>
>    and another issue is that "unsigned" is shorthand for "unsigned int",
> so
> if you wanted to generalize the method to handle integers of the system's
> word size (as is the case with 64-bit Spur which will have 61-bit
> SmallIntegers, unlike the 31-bit SmallIntegers in 64-bit Squeak) you'd
> want
> to use "usqInt", not "unsigned".
>
> On Sat, Sep 6, 2014 at 8:45 PM, <[hidden email]> wrote:
>
>>
>> David T. Lewis uploaded a new version of VMMaker to project VM Maker:
>> http://source.squeak.org/VMMaker/VMMaker-dtl.350.mcz
>>
>> ==================== Summary ====================
>>
>> Name: VMMaker-dtl.350
>> Author: dtl
>> Time: 6 September 2014, 11:44:28.389 pm
>> UUID: 2ad132b0-5fb3-4580-b5a8-29af12c3cb81
>> Ancestors: VMMaker-dtl.349
>>
>> VMMaker 4.13.6
>>
>> Fix primitiveBitShift (primitive 17) for sqInt declared 64 bits, as in a
>> VM for 64-bit image format 68002.
>>
>> In image format 68002, bit shift left failed because of return type
>> limited to a 32-bit large integer, but internally the primitive
>> successfully shifted left into a variable declared as a 64 bit sqInt..
>> The
>> simple fix (implemented here) is to declare the variable as 32 bit
>> unsigned
>> to agree with the 32-bit logic of the existing primitive.
>>
>> Note that permitting a left shift into a 64 bit variable makes sense
>> generally, and the primitive could be recoded to accomodate this for
>> shift
>> left, with the primitive answering positive64BitIntegerFor: rather than
>> positive32BitIntegerFor: in the case of a shift left to allow for the
>> greater range (not implemented in this update).
>>
>> With this update, all KernelTests-Numbers tests pass for the 64-bit
>> image
>> format 68002.
>>
>> =============== Diff against VMMaker-dtl.349 ===============
>>
>> Item was changed:
>>   ----- Method: InterpreterPrimitives>>primitiveBitShift (in category
>> 'arithmetic integer primitives') -----
>>   primitiveBitShift
>>         | integerReceiver integerArgument shifted |
>> +       <var: #shifted type: 'unsigned'>
>> +
>>         integerArgument := self popInteger.
>>         integerReceiver := self popPos32BitInteger.
>>         self successful ifTrue: [
>>                 integerArgument >= 0 ifTrue: [
>>                         "Left shift -- must fail if we lose bits beyond
>> 32"
>>                         self success: integerArgument <= 31.
>>                         shifted := integerReceiver << integerArgument.
>>                         self success: (shifted >> integerArgument) =
>> integerReceiver.
>>                 ] ifFalse: [
>>                         "Right shift -- OK to lose bits"
>>                         self success: integerArgument >= -31.
>>                         shifted := integerReceiver >> (0 -
>> integerArgument).
>>                 ].
>>         ].
>>         self successful
>>                 ifTrue: [self push: (self positive32BitIntegerFor:
>> shifted)]
>>                 ifFalse: [self unPop: 2]!
>>
>> Item was changed:
>>   ----- Method: VMMaker class>>versionString (in category 'version
>> testing') -----
>>   versionString
>>
>>         "VMMaker versionString"
>>
>> +       ^'4.13.6'!
>> -       ^'4.13.7'!
>>
>>
>
>
> --
> best,
> Eliot
>

 
Hi,

On 08.09.2014, at 23:23, David T. Lewis <[hidden email]> wrote:

>
> Hi Eliot,
>
> Agreed, the primitive will need to be rewritten to work with a 64-bit
> SmallInteger. There may be other integer primitives that will need
> attention too, although I have not looked.
>

Having tried implementing other SqueakVMs, my impression is, that the
SmallInt-is-31-bit assumption is like everywhere. Starting with some
int-primitives and not ending with bitBlt. We really have to be careful
here.

Best
        -Tobias

> Dave
>
>> Hi David,
>>
>> On Mon, Sep 8, 2014 at 12:18 PM, David T. Lewis <[hidden email]>
>> wrote:
>>
>>>
>>> I know that "unsigned" means "unsigned int". That is the intent.
>>>
>>> With the primitive as currently implemented, that variable must be 32
>>> bits, otherwise the shift left can successfully produce a five byte
>>> large
>>> integer that is truncated to four without failing the primitive. This
>>> change is to fix the current implementation of the primitive in the case
>>> of sizeof(sqInt) == 8.
>>>
>>
>> OK, then it is fixing it in a way that will break a 64-bit implementation
>> that uses 64-bit SmallIntegers.   Personally I find the method defective
>> (for reasons already stated), and will be rewriting it soon.
>>
>>
>>> Dave
>>>
>>>> Hi David,
>>>>
>>>>   and another issue is that "unsigned" is shorthand for "unsigned
>>> int",
>>>> so
>>>> if you wanted to generalize the method to handle integers of the
>>> system's
>>>> word size (as is the case with 64-bit Spur which will have 61-bit
>>>> SmallIntegers, unlike the 31-bit SmallIntegers in 64-bit Squeak) you'd
>>>> want
>>>> to use "usqInt", not "unsigned".
>>>>
>>>> On Sat, Sep 6, 2014 at 8:45 PM, <[hidden email]> wrote:
>>>>
>>>>>
>>>>> David T. Lewis uploaded a new version of VMMaker to project VM Maker:
>>>>> http://source.squeak.org/VMMaker/VMMaker-dtl.350.mcz
>>>>>
>>>>> ==================== Summary ====================
>>>>>
>>>>> Name: VMMaker-dtl.350
>>>>> Author: dtl
>>>>> Time: 6 September 2014, 11:44:28.389 pm
>>>>> UUID: 2ad132b0-5fb3-4580-b5a8-29af12c3cb81
>>>>> Ancestors: VMMaker-dtl.349
>>>>>
>>>>> VMMaker 4.13.6
>>>>>
>>>>> Fix primitiveBitShift (primitive 17) for sqInt declared 64 bits, as
>>> in a
>>>>> VM for 64-bit image format 68002.
>>>>>
>>>>> In image format 68002, bit shift left failed because of return type
>>>>> limited to a 32-bit large integer, but internally the primitive
>>>>> successfully shifted left into a variable declared as a 64 bit
>>> sqInt..
>>>>> The
>>>>> simple fix (implemented here) is to declare the variable as 32 bit
>>>>> unsigned
>>>>> to agree with the 32-bit logic of the existing primitive.
>>>>>
>>>>> Note that permitting a left shift into a 64 bit variable makes sense
>>>>> generally, and the primitive could be recoded to accomodate this for
>>>>> shift
>>>>> left, with the primitive answering positive64BitIntegerFor: rather
>>> than
>>>>> positive32BitIntegerFor: in the case of a shift left to allow for the
>>>>> greater range (not implemented in this update).
>>>>>
>>>>> With this update, all KernelTests-Numbers tests pass for the 64-bit
>>>>> image
>>>>> format 68002.
>>>>>
>>>>> =============== Diff against VMMaker-dtl.349 ===============
>>>>>
>>>>> Item was changed:
>>>>>  ----- Method: InterpreterPrimitives>>primitiveBitShift (in category
>>>>> 'arithmetic integer primitives') -----
>>>>>  primitiveBitShift
>>>>>        | integerReceiver integerArgument shifted |
>>>>> +       <var: #shifted type: 'unsigned'>
>>>>> +
>>>>>        integerArgument := self popInteger.
>>>>>        integerReceiver := self popPos32BitInteger.
>>>>>        self successful ifTrue: [
>>>>>                integerArgument >= 0 ifTrue: [
>>>>>                        "Left shift -- must fail if we lose bits
>>> beyond
>>>>> 32"
>>>>>                        self success: integerArgument <= 31.
>>>>>                        shifted := integerReceiver <<
>>> integerArgument.
>>>>>                        self success: (shifted >> integerArgument) =
>>>>> integerReceiver.
>>>>>                ] ifFalse: [
>>>>>                        "Right shift -- OK to lose bits"
>>>>>                        self success: integerArgument >= -31.
>>>>>                        shifted := integerReceiver >> (0 -
>>>>> integerArgument).
>>>>>                ].
>>>>>        ].
>>>>>        self successful
>>>>>                ifTrue: [self push: (self positive32BitIntegerFor:
>>>>> shifted)]
>>>>>                ifFalse: [self unPop: 2]!
>>>>>
>>>>> Item was changed:
>>>>>  ----- Method: VMMaker class>>versionString (in category 'version
>>>>> testing') -----
>>>>>  versionString
>>>>>
>>>>>        "VMMaker versionString"
>>>>>
>>>>> +       ^'4.13.6'!
>>>>> -       ^'4.13.7'!
>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> best,
>>>> Eliot
>>>>
>>>
>>>
>>>
>>
>>
>> --
>> best,
>> Eliot