PA question

[Jeffrey A Law]

  In message < 10010092103.AA23141@vlsi1.ultra.nyu.edu >you write:
  > In pa.h, GO_IF_LEGITIMATE_ADDRESS has comments that claims that REG+REG is
  > a valid address, but I don't see the code that allows it.  Am I missing
  > something or is the comment wrong?
You can't use it because of how the space is selected (from the upper two
bits of the base register, not the full effective address).  Since GCC
doesn't properly keep track of the base vs index, we can't make good
use of the reg+reg addressing mode.

We don't consider it valid, but instead have special patterns to detect the
cases where we can figure out what the base register is.

jeff