[Vm-dev] Re: New Cog VMs available

Eliot Miranda eliot.miranda at gmail.com
Fri Apr 17 00:39:31 UTC 2015

On 16 Apr 2015, at 16:50, Eliot Miranda wrote:

> ... at http://www.mirandabanda.org/files/Cog/VM/VM.r3311/.
> These should fix the regression introduced by the map changes in 3308.  They certainly fix the two crashes I've looked at, one an update of a squeak trunk image and the other the startup of recent Newspeak images.  Apologies for the inconvenience.

Well, this is embarrassing as usual but I'm still seeing crashes in the image update.  So I'll have to look deeper.  At least the Newspeak fix was real, but it didn't fix everything.
> CogVM binaries as per VMMaker.oscog-eem.1204/r3311
> Cogits:
> Fix regression in map machinery due to adding AnnotationExtension scheme.
> findMapLocationForMcpc:inMethod: must not be confused by IsDisplacementX2N
> bytes.  This is likely the cause of the recent crashes with r3308 and earlier.
> Introduce marryFrameCopiesTemps and use it to
> not copy temps in Spur context creation trampolines.
> Change initial usage counts to keep more recently jitted methods around for
> longer, and do *not* throw away PICs in freeOlderMethodsForCompaction, so that
> there's a better chance of Sista finding send and branch data for the tripping
> method.
> extendedPushBytecode /does/ need a frame.
> Don't save the header in a scratch register unless
> it is useful to do so in the Spur at:[put:] primitives.
> Fix slip in genGetNumBytesOf:into:.  And notice that
> genGetFormatOf:into:baseHeaderIntoScratch: et al can use byte access
> to get at format, as intended in the Spur header design.
> Fix unlinking dynamic super sends.
> Reduce false positives in access control violation reporting by marking the
> super send we actually use as privileged. Remove unused Newspeak bytecodes.
> Internal:
> Fix code generation bug surfaced by inline primitives.  On x86 movb N(%reg),%rl
> can only store into al, bl, cl & dl, whereas movzbl can store into any reg.  On
> ARM move byte also zero-extends.  So change definition of MoveMbrR to always
> zero-extend, use movzbl on x86 and remove all the MoveCq: 0 R: used to zero the
> bits of the target of a MoveMb:r:R:.  And now that we have
> genGetNumSlotsOf:into:, use it.
> Fix a slip in genTrinaryInlinePrimitive:, meet constraint that the target must
> be in ReceiverResultReg, and do a better job of register allocation there-in.
> Do dead code elimination for the branch following an inlined comparison (this
> is done in genBinaryInlineComparison:opFalse:destReg: copying the scheme in
> genSpecialSelectorEqualsEquals).
> Do register allocation in the right place in genUnaryInlinePrimitive:.
> Fix overflow slot access in genGetNumSlotsOf:into: et al.
> Fix several slips in inline primitive generation: Object>>at:put: needs to
> include a store check.  Some register allocation code was wrong.  Some results
> needed converting to SmallIntegers and recording results as pushed on the sim
> stack.
> Change callPrimitiveBytecode to genCallPrimitiveBytecode in the Cogit.
> remove the misnomer genConvertIntegerToSmallIntegerInScratchReg:
> Type of AbstractInstruction opcode must be unsigned now that we have
> more than 128 opcodes (XCHGRR pushed things over the top).
> Lay the groundwork for 32-bit intra-zone jumps and calls on ARM by introducing
> CallFull and JumpFull (and rewrites thereof) that are expected to span the full
> address space, leaving Call/JumpLong to span merely the 16mb code zone.  On x86
> CallFull and JumpFull simply default to Call/JumpLong.
> Replace bytecode trapIfNotInstanceOf by jumpIfNotInstanceOfOrPop.
> Rewrote the JIT logic for traps to be able to write trap trampolines calls at
> the end of the cogMethod.
> Refactor the slot store and store check machinery to take an inFrame: argument
> and hence deal with the store check in genInnerPrimitiveAtPut: on ARM.
> Fix limitation with MoveRXbrR; can only do movb from
> %al through %dl, so swap with %eax around movb.
> Fix mistake with genGetNumBytesOf:into: by refactoring
> genGetFormatOf:into:baseHeaderIntoScratch: into
> genGetBits:ofFormatByteOf:into:baseHeaderIntoScratch:
> and hence fetching and subtracting only odd bits of format.
> Correct the in-line primitive SmallInteger comparisons; CmpXR is confusing ;-)
> Fix var op var unsafe byte at:.  Result must be converted to SmallInteger.
> Correct the generated Slang for the new register allocation code by adding a
> read-before-written pass to C generation that initializes variables
> read-before-written with 0 (the C equivalent of nil).
> fix a bug where sometimes register allocation was marking ReceiverResultReg as
> dead whereas it was still alive.
> Added some abstraction over register allocation. This is now used in inline
> primitives.

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