Re: bit extract adjust_address versus scheduler

[Jim Wilson <wilson at tuliptree dot org>]

Alexandre Oliva wrote:
> It turned out that, even after fixing the MIPS-specific code, the
> problem was still there, because the generic code insisted in
> converting MEMs to byte_mode.

If you look at the doc for sign_extract/zero_extract, it clearly says 
that operand1 must have byte_mode.  Every port relies on this, and 
probably some optimization passes too.  It seems unsafe to change it in 
one place without making a wholesale change.

The aliasing code should be aware of this, and should handle 
sign_extract and zero_extract specially to avoid a problem.

The MIPS port changes the mode to BLKmode because we had aliasing 
problems before MEM_SIZE was introduced.  Since then, it should be 
redundant, but was left in to be safe.  Note that the MIPS port is 
emitting patterns with unspec that don't use sign_extract/zero_extract, 
so we need to set MEM_SIZE.  Other ports shouldn't have the same problem 
unless they are also using unspec.

Why is the existing code in mips.md that sets MEM_SIZE not working?

Jim