https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90273
--- Comment #13 from Richard Biener <rguenth at gcc dot gnu.org> --- (In reply to Richard Biener from comment #9) > Created attachment 46257 [details] > more aggressive variant > > More aggressive variant using a bitmap, simply keeping the last, does for > example > > @@ -243,7 +237,6 @@ > <bb 5> [local count: 43794188]: > # DEBUG BEGIN_STMT > i_28 = i_35 + 1; > - # DEBUG i => i_28 > # DEBUG d => 1 > # DEBUG i => i_28 > > note if there are debug temps those are still not DCEd even if not used. > In theory they should always have debug temp defs and uses in the same > BB so the backward walk could gather local uses. But that needs more > experiments / verification. As noted this one likely isn't safe considering # DEBUG D#1 => 123; # DEBUG a => D#1; # DEBUG D#1 => 234; # DEBUG b => D#1; where we'd remove the # DEBUG D#1 => 123; stmt. It has been said the situation can only occur with DEBUG_EXPR_DECL thus excempting those would work. That is, replacing D#1 with say 'c' won't ever happen (non-DEBUG_EXPR_DECL decls on the RHS, there just appear SSA names, invariants or DEBUG_EXPR_DECLs). With not DCEing DEBUG_EXPR_DECL binds on the testcase we go from > wc -l Unified_cpp_dom_events0-8.ii.046t.release_ssa 163546 Unified_cpp_dom_events0-8.ii.046t.release_ssa to > wc -l Unified_cpp_dom_events0-8.ii.046t.release_ssa 163626 Unified_cpp_dom_events0-8.ii.046t.release_ssa
