LEA or LOAD integer?

Question

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What’s the purpose of the LEA instruction?

Having just started assembly language I would like if someone could tell me the difference between using:

load R1,one[R0] rather than lea R1,1[R0]

when using the value in R1 only as an increment value. For the former, the data is given (one data 1) whereas for the latter data it is not.

I think it's weird to talk about assembly without specifying the CPU. — unwind, Dec 13 '12 at 11:17
I apologise, I'm very new to this. I'm using Sigma16. Only dealing with 16 bit words. — McGuile, Dec 13 '12 at 11:20

Paul R · Accepted Answer · 2012-12-13T11:21:21.697

1

In the first case you are loading data, in the second case you are loading an address.

E.g. if R0 contains 0x1000:

      addr   data
R0 -> 0x1000 0x42
             0x48
             0x49
             0x43
             0x30

then load R1,1[R0] will load 0x4849 into R1 (assuming the load instruction is a 16 bit load, and the architecture is big endian), whereas lea R1,1[R0] will load 0x1001 into R1.

edited Dec 13 '12 at 11:21

answered Dec 13 '12 at 11:14

Paul R

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LEA or LOAD integer?

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