[Vm-dev] VM Maker: VMMaker-dtl.350.mcz

[David T. Lewis]

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.

Dave

>  Hi David,
>
> On Mon, Sep 8, 2014 at 12:18 PM, David T. Lewis <lewis at mail.msen.com>
> 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, <commits at source.squeak.org> 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
>