------- Additional Comments From jh at suse dot cz 2005-01-01 23:52 ------- Subject: Re: [4.0 Regression] unrecognisable insn in regclass on x86/amd64
> > ------- Additional Comments From pinskia at gcc dot gnu dot org 2005-01-01 > 22:33 ------- > (In reply to comment #21) > > This is the original thread which leads to this regession: > > > > http://gcc.gnu.org/ml/gcc/2004-11/threads.html#00839 > > If you notice this works on all other targets other than x86/x86_64 which > means that it is a latent bug > in the x86 back-end. the problem seems to be loop optimizer taking the (const:SI (plus:SI (symbol_ref:SI ("foo") [flags 0x58] <var_decl 0xb7d5e828 foo>) (const_int 8 [0x8])) construct from REG_EQUAL note and throwing it into emit_move_insn without any care. I don't think emit_move_insn is required to deal with arbitary constant operand like this, so it seems to me that correct (and safe) way is to prevent loop from this idea... I am testing attached patch. But we might also teach move expander to decompose the CONST and legitimize it as we do for usual variable references... Honza Index: loop.c =================================================================== RCS file: /cvs/gcc/gcc/gcc/loop.c,v retrieving revision 1.518 diff -c -3 -p -r1.518 loop.c *** loop.c 18 Dec 2004 07:55:35 -0000 1.518 --- loop.c 1 Jan 2005 23:47:22 -0000 *************** scan_loop (struct loop *loop, int flags) *** 1149,1160 **** Otherwise, only use the REG_EQUAL contents if a REG_RETVAL note is present. */ temp = find_reg_note (p, REG_EQUIV, NULL_RTX); ! if (temp) src = XEXP (temp, 0), move_insn = 1; else { temp = find_reg_note (p, REG_EQUAL, NULL_RTX); ! if (temp && CONSTANT_P (XEXP (temp, 0))) src = XEXP (temp, 0), move_insn = 1; if (temp && find_reg_note (p, REG_RETVAL, NULL_RTX)) { --- 1149,1161 ---- Otherwise, only use the REG_EQUAL contents if a REG_RETVAL note is present. */ temp = find_reg_note (p, REG_EQUIV, NULL_RTX); ! if (temp && general_operand (XEXP (temp, 0), VOIDmode)) src = XEXP (temp, 0), move_insn = 1; else { temp = find_reg_note (p, REG_EQUAL, NULL_RTX); ! if (temp && CONSTANT_P (XEXP (temp, 0)) ! && LEGITIMATE_CONSTANT_P (XEXP (temp, 0))) src = XEXP (temp, 0), move_insn = 1; if (temp && find_reg_note (p, REG_RETVAL, NULL_RTX)) { -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18910
