------- Comment #2 from dann at godzilla dot ics dot uci dot edu 2006-03-30 16:43 ------- (In reply to comment #1) > Note that this may be also PRE confusing SCEV in presence of loop headers.
Talking about PRE, here's a maybe interesting observation in the PRE dump: <L7>:; pretmp.30_53 = Int_Loc.0_4 * 200; pretmp.32_23 = (int[50] *) pretmp.30_53; pretmp.32_11 = pretmp.32_23 + Arr_2_Par_Ref_30; goto <bb 4> (<L2>); <L6>:; pretmp.27_59 = Int_Loc.0_4 * 200; pretmp.28_45 = (int[50] *) pretmp.27_59; pretmp.28_49 = Arr_2_Par_Ref_30 + pretmp.28_45; # Int_Index_37 = PHI <Int_Index_58(7), Int_Loc_3(5)>; <L0>:; D.1544_54 = pretmp.27_59; D.1545_55 = pretmp.28_45; D.1546_56 = pretmp.28_49; (*D.1546_56)[Int_Index_37] = Int_Loc_3; Int_Index_58 = Int_Index_37 + 1; if (D.1548_41 >= Int_Index_58) goto <L8>; else goto <L9>; <L8>:; goto <bb 3> (<L0>); <L9>:; # prephitmp.33_40 = PHI <D.1546_56(8), pretmp.32_11(6)>; # prephitmp.33_18 = PHI <D.1545_55(8), pretmp.32_23(6)>; # prephitmp.31_25 = PHI <D.1544_54(8), pretmp.30_53(6)>; Compare pretmp.28_49 with pretmp.32_11, why are the arguments in a different order? Is there something unstable in the PRE algorithm? One has to wonder what are the tree-ch effects on more complex loops. It might be interesting test SPEC with and without tree-ch... -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26944
