Problem with peephole to peephole2 conversion

[Ashwin <ashwin at codito dot com>]

I am converting peepholes to peephole2's. However, after compiling the 
kernel with the patched build, I get size regressions. Although the 
obj-dump shows that the peephole should have matched, it is actually not 
getting matched. This is because the pattern to be matched is not 
present at the time of peephole2 pass (it is a 3 insn pattern, out of 
which 2 are together, but the third one is put in later by the 
scheduler) The pattern matches in the original peephole pass because the 
peephole pass happens just before assembly generation, when the 3 insns 
are present together.  Has anybody encountered a similar problem? Does 
this mean that peephole2 and peephole both should be kept on.

Secondly, after taking a look at other ports, i realised that all are 
using peep2_dead_reg_p instead of dead_or_set_p to check if a register 
is dead. The former is smarter than the later in the sense that it also 
checks if the current insn "sets" the register which is to be verified 
as dead. So, why do other ports use peep2_reg_dead_p instead of 
dead_or_set_p. Pls help me to find the advantages of using 
peep2_reg_dead_p over its counterpart.