Mutant pharo-project#594, Reverting [ Replace #ifTrue: receiver with true ] on method [ markAndShouldScan: ] KILLED by 1/10 test cases.

Author: hogoww

smalltalksrc/VMMaker/SpurMemoryManager.class.st

@@ -8159,32 +8159,36 @@ SpurMemoryManager >> markAllUnscannedEphemerons [
 
 { #category : #'gc - global' }
 SpurMemoryManager >> markAndShouldScan: objOop [
-
 	"Helper for markAndTrace:.
 	 Mark the argument, and answer if its fields should be scanned now.
 	 Immediate objects don't need to be marked.
 	 Already marked objects have already been processed.
 	 Pure bits objects don't need scanning, although their class does.
 	 Weak objects should be pushed on the weakling stack.
 	 Anything else need scanning."
-
-	<inline: true>
 	| format |
-	true ifTrue: [ ^ false ].
+	<inline: true>
+	(self isImmediate: objOop) ifTrue:
+		[^false].
+	"if markAndTrace: is to follow and eliminate forwarding pointers
+	 in its scan it cannot be handed an r-value which is forwarded."
 	self assert: (self isForwarded: objOop) not.
-	(self isMarked: objOop) ifTrue: [ ^ false ].
+	(self isMarked: objOop) ifTrue:
+		[^false].
 	self setIsMarkedOf: objOop to: true.
 	format := self formatOf: objOop.
-	(self isPureBitsFormat: format) ifTrue: [ "Avoid tracing classes of non-objects on the heap, e.g. IRC caches, Sista counters.""avoid pushing non-pointer objects on the markStack."
-		(self classIndexOf: objOop) > self lastClassIndexPun ifTrue: [ 
-			self markAndTraceClassOf: objOop ].
-		^ false ].
-	format = self weakArrayFormat ifTrue: [ "push weaklings on the weakling stack to scan later"
-		self push: objOop onObjStack: weaklingStack.
-		^ false ].
-	(format = self ephemeronFormat and: [ 
-		 self activeAndDeferredScan: objOop ]) ifTrue: [ ^ false ].
-	^ true
+	(self isPureBitsFormat: format) ifTrue: "avoid pushing non-pointer objects on the markStack."
+		["Avoid tracing classes of non-objects on the heap, e.g. IRC caches, Sista counters."
+		 (self classIndexOf: objOop) > self lastClassIndexPun ifTrue:
+			[self markAndTraceClassOf: objOop].
+		 ^false].
+	format = self weakArrayFormat ifTrue: "push weaklings on the weakling stack to scan later"
+		[self push: objOop onObjStack: weaklingStack.
+		 ^false].
+	(format = self ephemeronFormat
+	 and: [self activeAndDeferredScan: objOop]) ifTrue:
+		[^false].
+	^true
 ]
 
 { #category : #'gc - global' }