On Thu, Mar 31, 2016 at 2:27 PM, commits@source.squeak.org wrote:

Eliot Miranda uploaded a new version of VMMaker to project VM Maker: http://source.squeak.org/VMMaker/VMMaker.oscog-eem.1755.mcz

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

Name: VMMaker.oscog-eem.1755 Author: eem Time: 1 January 1970, 2:26:33.237515 pm

^^Ouch^^ !! That's what one gets for living on the bleeding edge :-/

UUID: adcfc67f-a856-48b8-aef2-71ff6275a903 Ancestors: VMMaker.oscog-nice.1754

Spur Cogit: Add a compile-time flag, CheckRememberedInTrampoline, that controls whether the remembered check is generated in-line or in the trampoline. If checked in the trampoline and on 64-bits use one memory access to get the header and share the access between the IMMUTABILITY check and the rememberedBit check. Factor out the rememberedBit check into its own method.

The default leaves the code unchanged. I doubt that the option will improve anything significantly; measuring the generated code in the simulator the option saves only 0.6% of generated code. But it's so lovely being able to explore the question in a couple of hours instead of at least a day or two in C.

Here's the data: CRIT=CheckRememberedInTrampoline; this methid is the last method generated in a listener image before it prompts the user: IMMTABILITY: 16r93F80 <-> 16r940E8: method: 16rC582F8 prim 117 selector: 16r6D12C8 primRead:into:startingAt:count: IMMTABILICRIT: 16r93250 <-> 16r933B8: method: 16rC582F8 prim 117 selector: 16r6D12C8 primRead:into:startingAt:count: VANILLA: 16r91C00 <-> 16r91D68: method: 16rC582F8 prim 117 selector: 16r6D12C8 primRead:into:startingAt:count: VANILLACRIT: 16r90D80 <-> 16r90EE8: method: 16rC582F8 prim 117 selector: 16r6D12C8 primRead:into:startingAt:count: 16r93F80 - 16r93250 / 16r93250 * 100.0 0.5601422920704027 16r91C00 - 16r90D80 / 16r90D80 * 100.0 0.6256742179072277

And interestingly IMMUTABILITY adds only 1.5% to the code bulk; writes are rare. 16r93F80 - 16r91C00 / 16r91C00 * 100.0 1.5222984562607205 16r93250 - 16r90D80 / 16r90D80 * 100.0 1.5884573894282634

=============== Diff against VMMaker.oscog-nice.1754 ===============

Item was added:

• ----- Method: CogObjectRepresentation class>>initializeMiscConstants (in

category 'initialization') -----

• initializeMiscConstants

•   "Override to avoid inheriting (and hence repeating) VMClass
  

class>>initializeMiscConstants.

•    Subclasses that have misc constants to initialize will override
  

further."!

Item was changed: CogObjectRepresentation subclass: #CogObjectRepresentationForSpur instanceVariableNames: 'ceScheduleScavengeTrampoline ceSmallActiveContextInMethodTrampoline ceSmallActiveContextInBlockTrampoline ceLargeActiveContextInMethodTrampoline ceLargeActiveContextInBlockTrampoline ceStoreCheckContextReceiverTrampoline ceStoreTrampolines'

•   classVariableNames: 'CheckRememberedInTrampoline
  

NumStoreTrampolines'

•   classVariableNames: 'NumStoreTrampolines'
    poolDictionaries: 'VMBytecodeConstants VMSqueakClassIndices'
    category: 'VMMaker-JIT'!
  
  

Item was added:

• ----- Method: CogObjectRepresentationForSpur

class>>initializeMiscConstants (in category 'initialization') -----

• initializeMiscConstants

•   CheckRememberedInTrampoline := initializationOptions at:
  

#CheckRememberedInTrampoline ifAbsent: [false]!

Item was added:

• ----- Method:

CogObjectRepresentationForSpur>>genCheckRememberedBitOf:scratch: (in category 'compile abstract instructions') -----

• genCheckRememberedBitOf: objReg scratch: scratchReg

•   "Check the remembered bit of the object in objReg; answer the jump
  

taken if the bit is already set.

•    Only need to fetch the byte containing it, which reduces the size
  

of the mask constant."

•   | rememberedBitByteOffset mask |
  

•   rememberedBitByteOffset := cogit backEnd isBigEndian
  

ifTrue: [objectMemory baseHeaderSize - 1 - (objectMemory rememberedBitShift // 8)]

ifFalse:[objectMemory rememberedBitShift // 8].

•   mask := 1 << (objectMemory rememberedBitShift \\ 8).
  

•   cogit MoveMb: rememberedBitByteOffset r: objReg R: scratchReg.
  

•   cogit TstCq: mask R: scratchReg.
  

•   ^cogit JumpNonZero: 0!
  
  

Item was changed: ----- Method: CogObjectRepresentationForSpur>>genStoreCheckReceiverReg:valueReg:scratchReg:inFrame: (in category 'compile abstract instructions') ----- genStoreCheckReceiverReg: destReg valueReg: valueReg scratchReg: scratchReg inFrame: inFrame "Generate the code for a store check of valueReg into destReg."

•   | jmpImmediate jmpDestYoung jmpSourceOld jmpAlreadyRemembered |
  

•   | jmpImmediate jmpDestYoung jmpSourceOld jmpAlreadyRemembered mask
  

rememberedBitByteOffset | <var: #jmpImmediate type: #'AbstractInstruction *'> <var: #jmpDestYoung type: #'AbstractInstruction *'> <var: #jmpSourceOld type: #'AbstractInstruction *'> <var: #jmpAlreadyRemembered type: #'AbstractInstruction *'> "Is value stored an immediate? If so we're done" jmpImmediate := self genJumpImmediate: valueReg. "Get the old/new boundary in scratchReg" cogit MoveCw: objectMemory storeCheckBoundary R: scratchReg. "Is target young? If so we're done" cogit CmpR: scratchReg R: destReg. "N.B. FLAGS := destReg - scratchReg" jmpDestYoung := cogit JumpBelow: 0. "Is value stored old? If so we're done." cogit CmpR: scratchReg R: valueReg. "N.B. FLAGS := valueReg - scratchReg" jmpSourceOld := cogit JumpAboveOrEqual: 0. "value is young and target is old.

•    Need to remember this only if the remembered bit is not already
  

set."

•   CheckRememberedInTrampoline ifFalse:
  

•           [jmpAlreadyRemembered := self genCheckRememberedBitOf:
  

destReg scratch: scratchReg].

•    Need to remember this only if the remembered bit is not already
  

set.

•    Test the remembered bit.  Only need to fetch the byte containing
  

it,

•    which reduces the size of the mask constant."
  

•   rememberedBitByteOffset := jmpSourceOld isBigEndian
  

ifTrue: [objectMemory baseHeaderSize - 1 - (objectMemory rememberedBitShift // 8)]

ifFalse:[objectMemory rememberedBitShift // 8].

•   mask := 1 << (objectMemory rememberedBitShift \\ 8).
  

•   cogit MoveMb: rememberedBitByteOffset r: destReg R: scratchReg.
  

•   cogit AndCq: mask R: scratchReg.
  

•   jmpAlreadyRemembered := cogit JumpNonZero: 0.
    "Remembered bit is not set.  Call store check to insert dest into
  

remembered table." self assert: destReg = ReceiverResultReg. cogit evaluateTrampolineCallBlock: [cogit CallRT: ceStoreCheckTrampoline] protectLinkRegIfNot: inFrame. jmpImmediate jmpTarget: (jmpDestYoung jmpTarget: (jmpSourceOld jmpTarget:

•           cogit Label)).
  

•   CheckRememberedInTrampoline ifFalse:
  

•           [jmpAlreadyRemembered jmpTarget: jmpSourceOld
  

getJmpTarget].

•   (jmpAlreadyRemembered jmpTarget:
  

•           cogit Label))).
    ^0!
  
  

Item was added:

• ----- Method: CogObjectRepresentationForSpur>>genStoreCheckTrampoline

(in category 'initialization') -----

• genStoreCheckTrampoline

•   | jumpSC |
  

•   <var: #jumpSC type: #'AbstractInstruction *'>
  

•   <inline: true>
  

•   CheckRememberedInTrampoline ifTrue:
  

•           [cogit zeroOpcodeIndex.
  

•            jumpSC := self genCheckRememberedBitOf: ReceiverResultReg
  

scratch: cogit backEnd cResultRegister.

•            self assert: jumpSC opcode = JumpNonZero.
  

•            jumpSC opcode: JumpZero.
  

•            cogit RetN: 0.
  

•            jumpSC jmpTarget: cogit Label].
  

•   ^cogit
  

•           genTrampolineFor: #remember:
  

•           called: 'ceStoreCheckTrampoline'
  

•           numArgs: 1
  

•           arg: ReceiverResultReg
  

•           arg: nil
  

•           arg: nil
  

•           arg: nil
  

•           regsToSave: (cogit callerSavedRegMask bitClear: (cogit
  

registerMaskFor: ReceiverResultReg))

•           pushLinkReg: true
  

•           resultReg: cogit returnRegForStoreCheck
  

•           appendOpcodes: CheckRememberedInTrampoline!
  
  

Item was changed: ----- Method: CogObjectRepresentationForSpur>>genStoreTrampolineCalled:instVarIndex: (in category 'initialization') ----- genStoreTrampolineCalled: trampolineName instVarIndex: instVarIndex "Convention: - RcvrResultReg holds the object mutated. If immutability failure: - TempReg holds the instance variable index mutated if instVarIndex > numDedicatedStoreTrampoline - ClassReg holds the value to store Registers are not lived across this trampoline as the immutability failure may need new stack frames."

•   | jumpSC jumpRC |
  

•   | jumpSC |
    <option: #IMMUTABILITY>
    <var: #trampolineName type: #'char *'>
    <var: #jumpSC type: #'AbstractInstruction *'>
  

•   <var: #jumpRC type: #'AbstractInstruction *'>
    <inline: false>
    cogit zeroOpcodeIndex.
    "SendNumArgsReg is mutated but we don't care as register are not
  

live across the trampoline. There is no reason why registers cannot be saved over the remember: call, but since the immutability check is a suspension point, registers cannot remain live." jumpSC := self genJumpMutable: ReceiverResultReg scratchReg: SendNumArgsReg. cogit compileTrampolineFor: #ceCannotAssignTo:withIndex:valueToAssign: numArgs: 3 arg: ReceiverResultReg arg: (instVarIndex < (NumStoreTrampolines - 1) ifTrue: [cogit trampolineArgConstant: instVarIndex] ifFalse: [TempReg]) arg: ClassReg arg: nil regsToSave: cogit emptyRegisterMask pushLinkReg: true resultReg: NoReg.

    "Store check"
    jumpSC jmpTarget: cogit Label.

•   "If on 64-bits and doing the remembered bit test here, we can
  

combine the tests to fetch the header once."

•   CheckRememberedInTrampoline ifTrue:
  

•           [objectMemory wordSize = 8
  

•                   ifTrue:
  

•                           [cogit TstCq: 1 << objectMemory
  

rememberedBitShift R: SendNumArgsReg.

•                            jumpRC := cogit JumpZero: 0.
  

•                            cogit RetN: 0]
  

•                   ifFalse:
  

•                           [jumpRC := self genCheckRememberedBitOf:
  

ReceiverResultReg scratch: SendNumArgsReg.

•                            self assert: jumpRC opcode = JumpNonZero.
  

•                            jumpRC opcode: JumpZero.
  

•                            cogit RetN: 0].
  

•            jumpRC jmpTarget: cogit Label].
    ^ cogit genTrampolineFor: #remember:
            called: trampolineName
            numArgs: 1
            arg: ReceiverResultReg
            arg: nil
            arg: nil
            arg: nil
            regsToSave: cogit emptyRegisterMask
            pushLinkReg: true
            resultReg: NoReg
            appendOpcodes: true!
  
  

Item was changed: ----- Method: CogObjectRepresentationForSpur>>genStoreWithImmutabilityAndStoreCheckSourceReg:slotIndex:destReg:scratchReg:needRestoreRcvr: (in category 'compile abstract instructions') ----- genStoreWithImmutabilityAndStoreCheckSourceReg: sourceReg slotIndex: index destReg: destReg scratchReg: scratchReg needRestoreRcvr: needRestoreRcvr "Store check code is duplicated to use a single trampoline"

•   | immutableJump jmpImmediate jmpDestYoung jmpSourceOld
  

jmpAlreadyRemembered |

•   | immutableJump jmpImmediate jmpDestYoung jmpSourceOld
  

rememberedBitByteOffset jmpAlreadyRemembered mask | <var: #immutableJump type: #'AbstractInstruction *'> <var: #jmpImmediate type: #'AbstractInstruction *'> <var: #jmpDestYoung type: #'AbstractInstruction *'> <var: #jmpSourceOld type: #'AbstractInstruction *'> <var: #jmpAlreadyRemembered type: #'AbstractInstruction *'>

    immutableJump := self genJumpImmutable: destReg scratchReg:

scratchReg.

    cogit genTraceStores.

    "do the store"
    cogit MoveR: sourceReg
               Mw: index * objectMemory wordSize + objectMemory

baseHeaderSize r: destReg.

    "store check"
    jmpImmediate := self genJumpImmediate: sourceReg.
    "Get the old/new boundary in scratchReg"
    cogit MoveCw: objectMemory storeCheckBoundary R: scratchReg.
    "Is target young?  If so we're done"
    cogit CmpR: scratchReg R: destReg. "N.B. FLAGS := destReg -

scratchReg" jmpDestYoung := cogit JumpBelow: 0. "Is value stored old? If so we're done." cogit CmpR: scratchReg R: sourceReg. "N.B. FLAGS := valueReg - scratchReg" jmpSourceOld := cogit JumpAboveOrEqual: 0. "value is young and target is old.

•    Need to remember this only if the remembered bit is not already
  

set."

•   CheckRememberedInTrampoline ifFalse:
  

•           [jmpAlreadyRemembered := self genCheckRememberedBitOf:
  

destReg scratch: scratchReg].

•    Need to remember this only if the remembered bit is not already
  

set.

•    Test the remembered bit.  Only need to fetch the byte containing
  

it,

•    which reduces the size of the mask constant."
  

•   rememberedBitByteOffset := jmpSourceOld isBigEndian
  

ifTrue: [objectMemory baseHeaderSize - 1 - (objectMemory rememberedBitShift // 8)]

ifFalse:[objectMemory rememberedBitShift // 8].

•   mask := 1 << (objectMemory rememberedBitShift \\ 8).
  

•   cogit MoveMb: rememberedBitByteOffset r: destReg R: scratchReg.
  

•   cogit AndCq: mask R: scratchReg.
  

•   jmpAlreadyRemembered := cogit JumpNonZero: 0.
    "Set the inst var index for the benefit of the immutability check.
  

The trampoline will repeat the check to choose between the immutbality violation and the store check." immutableJump jmpTarget: cogit Label. self genStoreTrampolineCall: index. needRestoreRcvr ifTrue: [ cogit putSelfInReceiverResultReg ].

    jmpImmediate jmpTarget:
    (jmpDestYoung jmpTarget:
    (jmpSourceOld jmpTarget:

•           cogit Label)).
  

•   CheckRememberedInTrampoline ifFalse:
  

•           [jmpAlreadyRemembered jmpTarget: jmpSourceOld
  

getJmpTarget].

•   (jmpAlreadyRemembered jmpTarget:
  

•           cogit Label))).
  

•   ^ 0!
  
  

Item was changed: ----- Method: CogObjectRepresentationForSpur>>generateObjectRepresentationTrampolines (in category 'initialization') ----- generateObjectRepresentationTrampolines "Do the store check. Answer the argument for the benefit of the code generator; ReceiverResultReg may be caller-saved and hence smashed by this call. Answering it allows the code generator to reload ReceiverResultReg cheaply. In Spur the only thing we leave to the run-time is adding the receiver to the remembered set and setting its isRemembered bit." self cppIf: IMMUTABILITY ifTrue: [self cCode: [] inSmalltalk: [ceStoreTrampolines := CArrayAccessor on: (Array new: NumStoreTrampolines)]. 0 to: NumStoreTrampolines - 1 do: [:instVarIndex | ceStoreTrampolines at: instVarIndex put: (self

genStoreTrampolineCalled: (cogit

                                          trampolineName:

'ceStoreTrampoline'

                                          numArgs: instVarIndex

                                          limit: NumStoreTrampolines -

2.                                                  instVarIndex:
   

instVarIndex)]].

•   ceStoreCheckTrampoline := self genStoreCheckTrampoline.
  

•   ceStoreCheckTrampoline := cogit
  

genTrampolineFor: #remember:

called: 'ceStoreCheckTrampoline'

arg: ReceiverResultReg

regsToSave: (cogit callerSavedRegMask bitClear: (cogit registerMaskFor: ReceiverResultReg))

result: cogit returnRegForStoreCheck. ceStoreCheckContextReceiverTrampoline := self genStoreCheckContextReceiverTrampoline. ceScheduleScavengeTrampoline := cogit

          genTrampolineFor: #ceScheduleScavenge

          called: 'ceScheduleScavengeTrampoline'

          regsToSave: cogit callerSavedRegMask.
    ceSmallActiveContextInMethodTrampoline := self

genActiveContextTrampolineLarge: false inBlock: false called: 'ceSmallMethodContext'. ceSmallActiveContextInBlockTrampoline := self genActiveContextTrampolineLarge: false inBlock: true called: 'ceSmallBlockContext'. ceLargeActiveContextInMethodTrampoline := self genActiveContextTrampolineLarge: true inBlock: false called: 'ceLargeMethodContext'. ceLargeActiveContextInBlockTrampoline := self genActiveContextTrampolineLarge: true inBlock: true called: 'ceLargeBlockContext'!

Item was changed: ----- Method: Cogit class>>initializeMiscConstants (in category 'class initialization') ----- initializeMiscConstants super initializeMiscConstants. Debug := initializationOptions at: #Debug ifAbsent: [false]. (initializationOptions includesKey: #EagerInstructionDecoration) ifTrue: [EagerInstructionDecoration := initializationOptions at: #EagerInstructionDecoration] ifFalse: [EagerInstructionDecoration ifNil: [EagerInstructionDecoration := false]]. "speeds up single stepping but could lose fidelity"

    ProcessorClass := (initializationOptions at: #ISA ifAbsentPut:

[self objectMemoryClass defaultISA]) caseOf: { [#X64] -> [BochsX64Alien]. [#IA32] -> [BochsIA32Alien]. [#ARMv5] -> [GdbARMAlien]. [#MIPSEL] -> [MIPSELSimulator] }. CogCompilerClass := self activeCompilerClass. (CogCompilerClass withAllSuperclasses copyUpTo: CogAbstractInstruction) reverseDo: [:compilerClass| compilerClass initialize; initializeAbstractRegisters].

•   self objectMemoryClass objectRepresentationClass
  

initializeMiscConstants. "Our criterion for which methods to JIT is literal count. The default value is 60 literals or less." MaxLiteralCountForCompile := initializationOptions at: #MaxLiteralCountForCompile ifAbsent: [60]. "we special-case 0, 1 & 2 argument sends, N is numArgs >= 3" NumSendTrampolines := 4. "Currently not even the ceImplicitReceiverTrampoline contains object references." NumObjRefsInRuntime := 0.

    NSCSelectorIndex := (NSSendCache instVarNames indexOf: #selector)

• 1. NSCNumArgsIndex := (NSSendCache instVarNames indexOf: #numArgs) -

1.  NSCClassTagIndex := (NSSendCache instVarNames indexOf: #classTag)
   

• 1. NSCEnclosingObjectIndex := (NSSendCache instVarNames indexOf:

#enclosingObject) - 1. NSCTargetIndex := (NSSendCache instVarNames indexOf: #target) - 1. NumOopsPerNSC := NSSendCache instVarNames size.

    "Max size to alloca when compiling.
     Mac OS X 10.6.8 segfaults approaching 8Mb.
     Linux 2.6.9 segfaults above 11Mb.
     WIndows XP segfaults approaching 2Mb."
    MaxStackAllocSize := 1024 * 1024 * 3 / 2 !

Item was changed: ----- Method: VMBasicConstants class>>namesDefinedAtCompileTime (in category 'C translation') ----- namesDefinedAtCompileTime "Answer the set of names for variables that should be defined at compile time. Some of these get default values during simulation, and hence get defaulted in the various initializeMiscConstants methods. But that they have values should /not/ cause the code generator to do dead code elimination based on their default values." ^#( VMBIGENDIAN IMMUTABILITY STACKVM COGVM COGMTVM SPURVM

•           PharoVM
  

  "Pharo vs Squeak"

•           EnforceAccessControl
  

"Newspeak"

•           CheckRememberedInTrampoline)            "IMMUTABILITY"!
  

•           "Pharo vs Squeak" PharoVM
  

•           "Newspeak" EnforceAccessControl)!