Hi Dave,

On Sun, Dec 26, 2021 at 12:35 PM David T. Lewis <lewis@mail.msen.com> wrote:
 
My apologies, I intended this for the VMMaker inbox. I will move it there now.

no problem.

On Sun, Dec 26, 2021 at 12:23 PM <commits@source.squeak.org> wrote:
 
David T. Lewis uploaded a new version of VMMaker to project VM Maker:
http://source.squeak.org/VMMaker/VMMaker.oscog-dtl.3123.mcz

==================== Summary ====================

Name: VMMaker.oscog-dtl.3123
Author: dtl
Time: 26 December 2021, 12:55:15.357105 pm
UUID: a0d4db62-a6ac-4d9c-ba51-5eec2ce0c415
Ancestors: VMMaker.oscog-eem.3122

Support image formats 68533 and 7033. Let the image inform the VM that alternate bytecodes either are or are not in use, and remember the setting when writing or reading the image format number in a shapshot file header. Also support testing the current value of multipleBytecodeSetsActive, and listing the encoder names of supported bytecode sets.

This is cool. But let me suggest...
Item was added:
+ ----- Method: InterpreterPrimitives>>primitiveBytecodeSetsAvailable (in category 'other primitives') -----
+ primitiveBytecodeSetsAvailable
+       "Answer the encoder names for the supported bytecode sets."
+       <export: true>
+       | encoderNames |
+       argumentCount >0 ifTrue:
+               [^self primitiveFailFor: PrimErrBadNumArgs].
+       encoderNames := self instantiateClass: self classArray indexableSize: 3.
+       self storePointer: 0 ofObject: encoderNames withValue: (objectMemory stringForCString: 'EncoderForV3').
+       self storePointer: 1 ofObject: encoderNames withValue: (objectMemory stringForCString: 'EncoderForV3PlusClosures').
+       self storePointer: 2 ofObject: encoderNames withValue: (objectMemory stringForCString: 'EncoderForSistaV1').
+       self pop: 1 thenPush: encoderNames.
+ !

use self methodReturnValue: encoderNames instead of self pop: 1 thenPush: encoderNames.

Item was added:
+ ----- Method: InterpreterPrimitives>>primitiveMultipleBytecodeSetsActive (in category 'other primitives') -----
+ primitiveMultipleBytecodeSetsActive
+       "Given one boolean parameter, set multipleBytecodeSetsActive to inform
+        the VM that alternate bytecode sets such as SistaV1 are now in use and
+       that the image format number should be updated accordingly. With zero
+       parameters, answer the current value of multipleBytecodeSetsActive."
+
+       <export: true>
+       argumentCount >1 ifTrue:
+               [^self primitiveFailFor: PrimErrBadNumArgs].
+       argumentCount = 1
+               ifTrue: [self stackTop = objectMemory trueObject
+                       ifTrue: [self cppIf: MULTIPLEBYTECODESETS
+                               ifTrue: [multipleBytecodeSetsActive := true]
+                               ifFalse: [^self primitiveFailFor: PrimErrUnsupported]]
+                       ifFalse: [self stackTop = objectMemory falseObject
+                               ifTrue: [multipleBytecodeSetsActive := false]
+                               ifFalse:[^self primitiveFailFor: PrimErrBadArgument]]].
+       multipleBytecodeSetsActive
+               ifTrue: [self pop: argumentCount + 1 thenPush: objectMemory trueObject]
+               ifFalse: [self pop: argumentCount + 1 thenPush: objectMemory falseObject]. 
+ !

use self methodReturnBool: multipleBytecodeSetsActive instead of the last three lines.

Item was changed:
  InterpreterPrimitives subclass: #StackInterpreter
(excessive size, no diff calculated)

Item was changed:
  ----- Method: StackInterpreter class>>initializeMiscConstants (in category 'initialization') -----
  initializeMiscConstants

        super initializeMiscConstants.
        STACKVM := true.

        "These flags identify a GC operation (& hence a reason to leak check),
         or just operations the leak checker can be run for."
        GCModeFull := 1.                                "stop-the-world global GC"
        GCModeNewSpace := 2.            "Spur's scavenge, or V3's incremental"
        GCModeIncremental := 4.         "incremental global gc (Dijkstra tri-colour marking); as yet unimplemented"
        GCModeBecome := 8.                      "v3 post-become sweeping/Spur forwarding"
        GCCheckImageSegment := 16.      "just a flag for leak checking image segments"
        GCCheckFreeSpace := 32.         "just a flag for leak checking free space; Spur only"
        GCCheckShorten := 64.           "just a flag for leak checking object shortening operations; Spur only"
        GCCheckPrimCall := 128.         "just a flag for leak checking external primitive calls"

        StackPageTraceInvalid := -1.
        StackPageUnreached := 0.
        StackPageReachedButUntraced := 1.
        StackPageTraced := 2.

        DumpStackOnLowSpace := 0.
        MillisecondClockMask := 16r1FFFFFFF.
        "Note: The external primitive table should actually be dynamically sized but for the sake of inferior platforms (e.g., Mac :-) who cannot allocate memory in any reasonable way, we keep it static (and cross our fingers...)"
        MaxExternalPrimitiveTableSize := 4096. "entries"

        MaxJumpBuf := 32. "max. callback depth"
        FailImbalancedPrimitives := InitializationOptions at: #FailImbalancedPrimitives ifAbsentPut: [true].
        EnforceAccessControl := InitializationOptions at: #EnforceAccessControl ifAbsent: [true].

        ReturnToInterpreter := 1. "setjmp/longjmp code."

        "Because of a hack with callbacks in the non-threaded VM they must not conflct with the VM's tag bits."
        DisownVMForFFICall := 16.
+       DisownVMForThreading := 32.
+       
+       "The multiple bytecodes active bit in the image format number"
+       MultipleBytecodeSetsBitmask := 512.
-       DisownVMForThreading := 32
  !

Item was changed:
  ----- Method: StackInterpreter>>readableFormat: (in category 'image save/restore') -----
  readableFormat: imageVersion
        "Anwer true if images of the given format are readable by this interpreter.
         Allows a virtual machine to accept selected older image formats."
        <api>
+       ^ (self imageFormatVersion = (imageVersion bitAnd: ( -1 - MultipleBytecodeSetsBitmask))) "Ignore multiple bytecode support identifier"
+               or: [objectMemory hasSpurMemoryManagerAPI not "No compatibility version for Spur as yet"
-       ^imageVersion = self imageFormatVersion "Float words in platform-order"
-          or: [objectMemory hasSpurMemoryManagerAPI not "No compatibility version for Spur as yet"
                        and: [imageVersion = self imageFormatCompatibilityVersion]] "Float words in BigEndian order"!

Can we write this as
    is the image version a Spur version? if so...
        insist on exact match
    is the image a priori version? If so...
        filter the acceptable matches
    otherwise
        fail for unrecognised version
?

'cuz this way is more readable/commentable/extensible in the long run.

Item was changed:
  ----- Method: StackInterpreter>>writeImageFileIO (in category 'image save/restore') -----
  writeImageFileIO
        "Write the image header and heap contents to imageFile for snapshot. c.f. writeImageFileIOSimulation.
         The game below is to maintain 64-bit alignment for all putLong:toFile: occurrences."
        <inline: #never>
        | imageName headerStart headerSize f imageBytes bytesWritten sCWIfn okToWrite |
...
+       multipleBytecodeSetsActive
+               ifTrue: [self putWord32: (self imageFormatVersion bitOr: MultipleBytecodeSetsBitmask) toFile: f]
+               ifFalse: [self putWord32: self imageFormatVersion toFile: f].

why not extract this to e.g. self imageFormatVersionForSnapshot?

-       self putWord32: self imageFormatVersion toFile: f.
        self putWord32: headerSize toFile: f.
...

_,,,^..^,,,_
best, Eliot