Problem with ColouringRegisterAllocator

[bryce at kampjes.demon.co.uk]

Igor Stasenko writes:
 > in method addInterferenceEdge: firstRegister to: secondRegister
 > 
 > is stumbled upon error: key not found when it does:
 > 
 > secondNode := interferenceGraph at: secondRegister.
 > 
 > an interferenceGraph keys  = a Set(t9 t11 t14 t10 t2 t24 t22 t19 t25
 > t3 t8 t15 eax t20 t21 t16 t11 edx t17 t6 t3 t26 t12 t2 t4 t21 ecx t16
 > t12 t9 t23 t1 t5 t20 t13 t15 t14 t5 t27 t1 t6 t19 eax t13 t4 t17 t18
 > t28 t7 t8 t18 t10 t7)
 > 
 > and secondRegister = eax.
 > 
 > It looks like MedMachineRegister needs #= and #hash methods to make
 > things working correctly with dictionaries.
 > 
 > I'll try add these methods, lets see if issue will disappear.

There should only ever be one instance of each register. The bug is
creating the second one. That said, you may find it easier to
impleemnt = and hash than track it down. Using identity is a
deliberate design decision.

Having multiple versions of the same item may cause problems. I
think you may be OK with duplicate registers but am not sure.

 > Btw, i don't know why or where it creates another instance of same
 > register (MedMachineRegister name: #eax), in my code i using:
 > 'machine registerNamed: #eax', which should create instance only once,
 > and then return same instance for consequent calls.

Bryce