Find Min. Number of Temperory Variables ?

Question

Comments

is it 4?

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I got 5. what's the answer?

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Ans is Given as 5 ... But i m getting 4 .....
i cant understand why we there is need to assign temperory variable for u=8

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amul show your work.

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because all the previous variables p,q,t,s should be stored on R1 R2 R3 R4 and we need them in future when u comes up. we still requires all the values of R!,R2,R3,R4 in the future and hence can't substitute any register with value of u.

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ashwin u= s*p , here you can save register since s update before use so reuse it

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If there is no need to assign u=8 then we can do next operation using s i.e say t4 temperory variable.

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@Ashwin Kulkarni  please explain procedure to do such type of problem