[Vm-dev] VM Maker: VMMaker-dtl.350.mcz
eliot.miranda at gmail.com
Mon Sep 8 21:11:05 UTC 2014
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.
> > 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
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