On Tue, May 10, 2011 at 12:18 PM, Easwaran Raman <era...@google.com> wrote: > On Tue, May 3, 2011 at 9:40 AM, Easwaran Raman <era...@google.com> wrote: >> On Mon, May 2, 2011 at 8:37 PM, Jeff Law <l...@redhat.com> wrote: >>> -----BEGIN PGP SIGNED MESSAGE----- >>> Hash: SHA1 >>> >>> On 04/26/11 16:06, Easwaran Raman wrote: >>> >>>> >>>>> You're right. The patch has correctness issues. It is not possible to >>>>> simply not call add_wild_read because it also resets >>>>> active_local_stores and frees read_recs. During the local phase it >>>>> seems better to just treat calls as wild reads and reset >>>>> active_local_stores and free read_recs. I've now refactored >>>>> add_wild_read so that resetting active_local_stores and free read_recs >>>>> are in separate methods that can be called on non-const/non-memset >>>>> calls. In addition, I have added a non_frame_wild_read field in >>>>> insn_info to mark non-const and non-memset calls. >>>> >>>>> I've attached the revised patch. >>> Looking better. Just a few more things. >>> >>> Don't all locals escape if the callee has a static chain? Is that >>> handled anywhere? >>> >>> Don't you still have the potential for wild reads in dse_step5_nospill >>> (say from an asm)? if so, then the change can't be correct. >>> >>> Couldn't you just add a clause like this before the else-if? >>> >>> else if (insn_info->non_frame_wild_read) >>> { >>> if (dump_file) >>> fprintf (dump_file, "non-frame wild read\n"); >>> scan_reads_nospill (insn_info, v, NULL); >>> } >>> else if (insn_info->read_rec) >>> { >>> /* Leave this clause unchanged */ >>> } >>> >>> Am I missing something? >> >> I am not sure I understand the problem here. If there is a wild read >> from asm, the instruction has the wild_read flag set. The if statement >> checks if that flag is set and if so it clears the bitmap - which was >> the original behavior. Originally, only if read_rec is non NULL you >> need to recompute the kill set. Now, even if read_rec is NULL, >> non_frame_wild_read could be set requiring the kill set to be >> modified, which is what this patch does. In fact, isn't what you have >> written above the equivalent to what is in the patch as '/* Leave this >> clause unchanged */' is the same as >> >> if (dump_file) >> fprintf (dump_file, "regular read\n"); >> scan_reads_nospill (insn_info, v, NULL); >> >> >> -Easwaran >> > > Ping. I have changed the test case to use int and added another test > case that shows DSE doesn't happen when the struct instance is > volatile (wild_read gets set in that case) > >
One test failed on Linux/ia32: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49414 -- H.J.