On 4/11/19 3:04 AM, Jakub Jelinek wrote: > On Thu, Apr 11, 2019 at 09:54:24AM +0200, Richard Biener wrote: >>> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? >>> >>> During those 2 bootstraps/regtests, data.load_found has been set just >>> on the new testcase on ia32. >> >> Hmm, I wonder whether we really need to DCE calls after reload? >> That said, I'm not familiar enough with the code to check if the >> patch makes sense (can there ever be uses of the argument slots >> _after_ the call?). > > And here is the patch on top of the refactoring patch. > As for the argument slots after the call, hope Jeff and Vlad won't mind if I > copy'n'paste what they said on IRC yesterday: > law: vmakarov: in PR89965, is it valid RTL to store something in stack > argument slot and read it again before the call that uses that stack slot? > law: vmakarov: if yes, I have a rough idea what to do, but if stack argument > slots may be only stored and can be read only by a callee and not by > something else in the caller, then it is a RA issue > <vmakarov> jakub: i think it is not defined (or described). But the old > reload used equiv memory for long time to store value in memory. LRA just > uses the same approach. > <law> i think you're allowed to read it up to the call point, who "owns" the > contents of the slot after the call point is subject to debate :-) > <law> not sure if we defined things once a REG_EQUIV is on the MEM, but that > would tend to imply the memory is unchanging across the call > <law> (though one could ask how in the world the caller would know the callee > didn't clobber the slot....) > > 2019-04-11 Jakub Jelinek <ja...@redhat.com> > > PR rtl-optimization/89965 > * dce.c: Include rtl-iter.h. > (struct check_argument_load_data): New type. > (check_argument_load): New function. > (find_call_stack_args): Check for loads from stack slots still tracked > in sp_bytes and punt if any is found. > > * gcc.target/i386/pr89965.c: New test. OK. I'd probably update this comment:
> /* Walk backwards, looking for argument stores. The search stops > when seeing another call, sp adjustment or memory store other than > argument store. */ After this patch we'll also stop if we hit a load from an argument slot. jeff
