On Thu, Jun 6, 2013 at 5:10 PM, Bernd Schmidt <ber...@codesourcery.com> wrote: > On 06/06/2013 04:52 PM, Richard Biener wrote: >> + /* We cannot optimize away a static used in multiple functions (as >> + might happen in C++). */ >> + && !DECL_NONLOCAL(var) >> >> it may also happen trivially with inlining. Which means a local pass can >> never >> "remove" vars safely. > > This is why the pass isn't run if cgraph_function_possibly_inlined_p. > Tested by remove-local-statics-14b.c.
I see (how ugly ;)). Does that cover versioning via IPA CP as well for example? >> In theory we have IPA reference which tries to figure out whether a local >> static >> is read and/or written to (and from where). It's of course quite early >> analysis >> where FRE may not yet have optimized out all reads. >> >> But the trivial dead local static store elimination would simply eliminate >> all write-only and !TREE_ADDRESSABLE vars (and statements storing >> to it). >> >> For some reason this must be not enough so you write that local >> analysis code. >> >> Thus - I'm asking you to double-check a trivial implementation using >> the IPA reference result and double-check the issue with inlining >> introducing out-of-current-function uses. > > I'm not sure what you're asking for here. The IPA passes seem to run > much before PRE, and if you need an example why that's too early, try > the remove-local-statics-7.c testcase. Yes, that requires PRE. I'm sure there are cases your pass doesn't get either. I was asking whether the particular benchmark would be optimized by the simple IPA reference method. Richard. > > Bernd >
