PowerPC assembler question

[Erik de Castro Lopo]

Hi all,

I'm trying to fix a problem in the PowerPC backend of the Glasgow
Haskell Compiler (GHC) and have a problem with the following
instruction form:

    lwz     30, .label - (1b)(31)

Reading the documentation I could find, I have figured out that this
loads a 16 bit value into register 30. How it calculates that 16 bit
value has got me somewhat flumoxed.

Anybody care to explain?

Cheers,
Erik
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Erik de Castro Lopo
http://www.mega-nerd.com/