[Pharo-vm] About primitiveMethodXray

Sept. 15, 2022

      Hi 

In CoInterpreter we can find 

initializePrimitiveTable
	super initializePrimitiveTable.
	PrimNumberHashMultiply := 159.
	self assert: (PrimitiveTable at: PrimNumberHashMultiply + 1) = #primitiveHashMultiply.

	#(216 253) do:
		[:pidx| self assert: (PrimitiveTable at: pidx + 1) = #primitiveFail].
	self assert: (PrimitiveTable at: 215 + 1) = #primitiveFlushCacheByMethod.
	PrimitiveTable
		at: 253 + 1 put: #primitiveCollectCogCodeConstituents;
		at: 215 + 1 put: #primitiveVoidVMStateForMethod;
		at: 216 + 1 put: #primitiveMethodXray

There is a primitive primitiveMethodXray :)

primitiveMethodXray
	"Lift the veil from a method and answer an integer describing the interior state
	 of its machine code.
	 Used for e.g. VM tests so they can verify they're testing what they think they're testing.
	 0 implies a vanilla method.
	 Bit 0 = method might be compiled to machine code
	 Bit 1 = method is currently compiled to machine code
	 Bit 2 = is compiled frameless.
	 Bit 3 = method refers to young object.
	 Bit 4 = method too big to be jitted (more than 64k of code, or needs more than 1.5Mb of stack space to compile)
	 Bit 5 = method contains unknown/unjittable bytecode
	 Bit 6 = method should not be jitted because it contains a primitive not to be called from machine code (unused)"
	| alreadyCogged flags cogMethod |
	<var: #cogMethod type: #'CogMethod *'>
	(self methodWithHeaderShouldBeCogged: (objectMemory methodHeaderOf: self stackTop))
		ifTrue:
			[alreadyCogged := self maybeMethodHasCogMethod: self stackTop.
			 flags := 1.
			 alreadyCogged ifFalse:
				[cogMethod := cogit cog: self stackTop selector: objectMemory nilObject.
				 (cogMethod = nil
				  and: [cogCompiledCodeCompactionCalledFor]) ifTrue:
					[self commenceCogCompiledCodeCompaction.
					 cogMethod := cogit cog: self stackTop selector: objectMemory nilObject].
			 cogMethod asInteger
				caseOf: {
					[MethodTooBig] -> [flags := 1 + 16].
					[EncounteredUnknownBytecode] -> [flags := 1 + 32].
					[ShouldNotJIT] -> [flags := 1 + 64] }
				otherwise: [self deny: (cogMethod asInteger between: MaxNegativeErrorCode and: NotFullyInitialized)]].
			 (flags = 1
			  and: [self maybeMethodHasCogMethod: self stackTop]) ifTrue:
				[cogMethod := self cogMethodOf: self stackTop.
				 flags := cogMethod stackCheckOffset = 0 ifTrue: [7] ifFalse: [3].
				 cogMethod cmRefersToYoung ifTrue:
					[flags := flags + 8].
				 alreadyCogged ifFalse:
					[cogit freeMethod: cogMethod]]]
		ifFalse: [flags := 0].
	self pop: 1 thenPush: (objectMemory integerObjectOf: flags)

and I wanted to execute it.

So on compiledMethod I defined a method

CompiledMethod >> xray 

	<primitive: 216>

and I did (Point>>#degrees) xray 
but when I execute I get a compiled method and not an integer.

So I probably do something silly.
But I would like to understand what.

Tx

[Pharo-vm] About primitiveMethodXray

stephane ducasse