[Vm-dev] VM Maker: VMMaker.oscog-lpc.1903.mcz

commits at source.squeak.org commits at source.squeak.org
Fri Jul 15 14:27:20 UTC 2016

Laura Perez Cerrato uploaded a new version of VMMaker to project VM Maker:

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

Name: VMMaker.oscog-lpc.1903
Author: lpc
Time: 15 July 2016, 11:24:50.786748 am
UUID: 338f00b4-6135-4904-97da-0528241e2a62
Ancestors: VMMaker.oscog-eem.1902

BitBltSimulation>>primitivePixelValueAtX:y: needs to be modified to allow the optimization mentioned in VMMaker.oscog-eem.1888's message. This modification is similar to those in that same commit.

=============== Diff against VMMaker.oscog-eem.1902 ===============

Item was changed:
  ----- Method: BitBltSimulation>>primitivePixelValueAtX:y: (in category 'primitives') -----
  primitivePixelValueAtX: xVal y: yVal
  	"returns the single pixel at x at y.
  	It does not handle LSB bitmaps right now.
  	If x or y are < 0, return 0 to indicate transparent (cf BitBlt>bitPeekerFromForm: usage).
  	Likewise if x>width or y>depth.
  	Fail if the rcvr doesn't seem to be a Form, or x|y seem wrong"
  	| rcvr bitmap depth ppW stride bitsSize word mask shift pixel |
  	rcvr := self primitive: 'primitivePixelValueAt' parameters: #(SmallInteger SmallInteger) receiver: #Oop.
  	"possible quick exit if x or y is -ve"
  	(xVal < 0 or: [ yVal < 0 ] ) ifTrue:[^interpreterProxy integerObjectOf: 0].
  	"check that rcvr is plausibly a Form or subclass"	
  	rcvr := interpreterProxy stackValue: interpreterProxy methodArgumentCount.
  	((interpreterProxy isPointers: rcvr) and: [(interpreterProxy slotSizeOf: rcvr) >= 4])
  		ifFalse: [^interpreterProxy primitiveFail].
  	"get the bits oop and width/height/depth"
  	bitmap := interpreterProxy fetchPointer: FormBitsIndex ofObject: rcvr.
  	(interpreterProxy isWordsOrBytes: bitmap) ifFalse: [^interpreterProxy primitiveFail].
  	width := interpreterProxy fetchInteger: FormWidthIndex ofObject: rcvr.
  	height := interpreterProxy fetchInteger: FormHeightIndex ofObject: rcvr.
  	depth := interpreterProxy fetchInteger: FormDepthIndex ofObject: rcvr.
  	"if width/height/depth are not integer, fail"
  	interpreterProxy failed ifTrue:[^nil].
  	"possible quick exit if x or y is >= extent of form. This also catches cases where the width/height are < 0"
  	(xVal >= width or: [ yVal >= height ] ) ifTrue:[^interpreterProxy integerObjectOf: 0].
  	"we don't handle LSB Forms yet"
  	depth < 0 ifTrue:[^interpreterProxy primitiveFail].
  	"OK so now we know we have a plausible Form, the width/height/depth/x/y are all reasonable and it's time to plunder the bitmap"
  	ppW := 32//depth. "pixels in each word"
  	stride := (width + (ppW  -1)) // ppW. "how many words per row of pixels"
  	bitsSize := interpreterProxy byteSizeOf: bitmap.
+ 	bitsSize >= (stride * height * 4 "bytes per word")
- 	bitsSize = (stride * height * 4 "bytes per word")
  		ifFalse: [^interpreterProxy primitiveFail].
  	word := interpreterProxy fetchLong32:(yVal * stride) + (xVal//ppW) ofObject: bitmap. "load the word that contains our target"
  	mask := 16rFFFFFFFF >> (32 - depth). "make a mask to isolate the pixel within that word"
  	shift := 32 - (((xVal bitAnd: ppW-1) + 1) * depth). "this is the tricky MSB part - we mask the xVal to find how far into the word we need, then add 1 for the pixel we're looking for, then * depth to get the bit shift"
  	pixel := (word >> shift) bitAnd: mask. "shift, mask and dim the lights"
  	^ pixel asPositiveIntegerObj "pop the incoming and push our answer"

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