On Thu, May 17, 2012 at 1:46 PM, Meador Inge <mead...@codesourcery.com> wrote: > On 05/17/2012 03:02 PM, Richard Sandiford wrote: > >> After agonising over this for a couple of days, I think it's probably >> the correct fix. What we're doing now would be valid if the only use of >> equiv_constant(x) were to substitute for x. The name and current use >> of the function obviously require equality though. >> >> Patch is OK, thanks. It might be worth extending fold_rtx and >> equiv_constant to set a flag that says whether the returned value >> is equivalent or simply one of many valid replacement values. >> We'd then be able to replace uses of registers like 142 with 0, >> while not replacing uses of 0 with 142. I don't know how much it >> would buy us though. That kind of thing is probably more of a job >> for fwprop. > > Thanks for the review. > >> Please add UL to the hex constants in the testcase. Not sure whether >> it matters for 16-bit int targets or not, but better safe than sorry :-) > > Fixed. > >> Also, rather than: >> >>> + /* Otherwise see if we already have a constant for the inner REG. >>> + Don't bother with paradoxical subregs because we have no way >>> + of knowing what the upper bytes are. */ >> >> how about: >> >> /* Otherwise see if we already have a constant for the inner REG, >> and if that is enough to calculate an equivalent constant for >> the subreg. Note that the upper bits of paradoxical subregs >> are undefined, so they cannot be said to equal anything. */ > > Sounds good to me. > > v2 OK? If so, would you mind committing for me? I don't have write access. >
The test fails on Linux/x86 and Linux/x86-64. -- H.J.
