<div dir="ltr">Hi David,<br><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Sep 8, 2014 at 12:18 PM, David T. Lewis <span dir="ltr"><<a href="mailto:lewis@mail.msen.com" target="_blank">lewis@mail.msen.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br>
I know that "unsigned" means "unsigned int". That is the intent.<br>
<br>
With the primitive as currently implemented, that variable must be 32<br>
bits, otherwise the shift left can successfully produce a five byte large<br>
integer that is truncated to four without failing the primitive. This<br>
change is to fix the current implementation of the primitive in the case<br>
of sizeof(sqInt) == 8.<br></blockquote><div><br></div><div>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.</div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
Dave<br>
<div class="HOEnZb"><div class="h5"><br>
> Hi David,<br>
><br>
> and another issue is that "unsigned" is shorthand for "unsigned int",<br>
> so<br>
> if you wanted to generalize the method to handle integers of the system's<br>
> word size (as is the case with 64-bit Spur which will have 61-bit<br>
> SmallIntegers, unlike the 31-bit SmallIntegers in 64-bit Squeak) you'd<br>
> want<br>
> to use "usqInt", not "unsigned".<br>
><br>
> On Sat, Sep 6, 2014 at 8:45 PM, <<a href="mailto:commits@source.squeak.org">commits@source.squeak.org</a>> wrote:<br>
><br>
>><br>
>> David T. Lewis uploaded a new version of VMMaker to project VM Maker:<br>
>> <a href="http://source.squeak.org/VMMaker/VMMaker-dtl.350.mcz" target="_blank">http://source.squeak.org/VMMaker/VMMaker-dtl.350.mcz</a><br>
>><br>
>> ==================== Summary ====================<br>
>><br>
>> Name: VMMaker-dtl.350<br>
>> Author: dtl<br>
>> Time: 6 September 2014, 11:44:28.389 pm<br>
>> UUID: 2ad132b0-5fb3-4580-b5a8-29af12c3cb81<br>
>> Ancestors: VMMaker-dtl.349<br>
>><br>
>> VMMaker 4.13.6<br>
>><br>
>> Fix primitiveBitShift (primitive 17) for sqInt declared 64 bits, as in a<br>
>> VM for 64-bit image format 68002.<br>
>><br>
>> In image format 68002, bit shift left failed because of return type<br>
>> limited to a 32-bit large integer, but internally the primitive<br>
>> successfully shifted left into a variable declared as a 64 bit sqInt..<br>
>> The<br>
>> simple fix (implemented here) is to declare the variable as 32 bit<br>
>> unsigned<br>
>> to agree with the 32-bit logic of the existing primitive.<br>
>><br>
>> Note that permitting a left shift into a 64 bit variable makes sense<br>
>> generally, and the primitive could be recoded to accomodate this for<br>
>> shift<br>
>> left, with the primitive answering positive64BitIntegerFor: rather than<br>
>> positive32BitIntegerFor: in the case of a shift left to allow for the<br>
>> greater range (not implemented in this update).<br>
>><br>
>> With this update, all KernelTests-Numbers tests pass for the 64-bit<br>
>> image<br>
>> format 68002.<br>
>><br>
>> =============== Diff against VMMaker-dtl.349 ===============<br>
>><br>
>> Item was changed:<br>
>> ----- Method: InterpreterPrimitives>>primitiveBitShift (in category<br>
>> 'arithmetic integer primitives') -----<br>
>> primitiveBitShift<br>
>> | integerReceiver integerArgument shifted |<br>
>> + <var: #shifted type: 'unsigned'><br>
>> +<br>
>> integerArgument := self popInteger.<br>
>> integerReceiver := self popPos32BitInteger.<br>
>> self successful ifTrue: [<br>
>> integerArgument >= 0 ifTrue: [<br>
>> "Left shift -- must fail if we lose bits beyond<br>
>> 32"<br>
>> self success: integerArgument <= 31.<br>
>> shifted := integerReceiver << integerArgument.<br>
>> self success: (shifted >> integerArgument) =<br>
>> integerReceiver.<br>
>> ] ifFalse: [<br>
>> "Right shift -- OK to lose bits"<br>
>> self success: integerArgument >= -31.<br>
>> shifted := integerReceiver >> (0 -<br>
>> integerArgument).<br>
>> ].<br>
>> ].<br>
>> self successful<br>
>> ifTrue: [self push: (self positive32BitIntegerFor:<br>
>> shifted)]<br>
>> ifFalse: [self unPop: 2]!<br>
>><br>
>> Item was changed:<br>
>> ----- Method: VMMaker class>>versionString (in category 'version<br>
>> testing') -----<br>
>> versionString<br>
>><br>
>> "VMMaker versionString"<br>
>><br>
>> + ^'4.13.6'!<br>
>> - ^'4.13.7'!<br>
>><br>
>><br>
><br>
><br>
> --<br>
> best,<br>
> Eliot<br>
><br>
<br>
<br>
</div></div></blockquote></div><br><br clear="all"><div><br></div>-- <br>best,<div>Eliot</div>
</div></div>