Hi David,
On Sun, 22 Oct 2006, David Daney wrote:
2006-10-22 Richard Sandiford <richard@codesourcery.com>
David Daney <ddaney@avtrex.com>
PR middle-end/29519
* rtlanal.c (nonzero_address_p): Remove check for values wrapping.
:REVIEWMAIL:
This is ugly. I agree with you and Richard that this optimization isn't
safe unless we can somehow prevent the RTL optimizers from creating the
problematic RTL that they currently do. But I also worry how much benefit
some platforms get from the current unsafe transformation, and whether
there'd be an observable performance degradation with this fix.
I think its best to apply this patch to mainline to allow the benchmarking
folks test whether there's any change. Likewise if someone could check
whether there are any/many code generation differences in cc1 files (or
similar), that'd go some way to silencing my potential concerns.