Revamped frame chain, useful for PPC?

[Andrew Cagney]

Jim,

Long long ago you mentioned that, to improve performance, you hacked the 
PPC code and core GDB so that it could do a light weight frame chain. 
That is, instead of a full frame prologue (aka, init frame saved regs / 
init extra frame info), it would just chain the frame pointer.

Can I suggest looking at the cagney-unwind-20030108-branch as it 
contains the revamped unwind mechanism.  In particular, it now leaves it 
to the target architecture to determine if/when additional prologue 
analysis should be performed.

See the function get_prev_frame() for the unwind sequence, and 
sentinel-frame / dummy-frame for specific frame implementations.

Andrew