Hi! As mentioned in the PR, we are miscompiling glibc on i686-linux, because the new indirect_jump_optimize mini-pass thinks that a insn which has REG_LABEL_OPERAND note necessarily has to set the target register to that label, while in the glibc case it is actually that label + some offset, where the offset is read from a table which contains other labels - this label differences.
The following patch changes it to just look at SET_SRC of single_set and/or REG_EQUAL note, and only consider those if one of them is a LABEL_REF. That alone broke lots of tests, which contain non-local gotos, so I had to add a check that we don't do anything in this mini-pass (like old ira.c code did) if there is REG_NON_LOCAL_GOTO note. Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk/5/4.9? Bernd has preapproved the patch, but that was before the REG_NON_LOCAL_GOTO changes. 2016-03-30 Jakub Jelinek <ja...@redhat.com> PR rtl-optimization/70460 * ira.c (indirect_jump_optimize): Don't substitute LABEL_REF with operand from REG_LABEL_OPERAND, instead substitute SET_SRC or REG_EQUAL note content if it is a LABEL_REF. Don't do anything for REG_NON_LOCAL_GOTO jumps. * gcc.c-torture/execute/pr70460.c: New test. --- gcc/ira.c.jj 2016-03-21 10:12:32.000000000 +0100 +++ gcc/ira.c 2016-03-30 19:06:42.883892088 +0200 @@ -3870,7 +3870,8 @@ indirect_jump_optimize (void) FOR_EACH_BB_REVERSE_FN (bb, cfun) { rtx_insn *insn = BB_END (bb); - if (!JUMP_P (insn)) + if (!JUMP_P (insn) + || find_reg_note (insn, REG_NON_LOCAL_GOTO, NULL_RTX)) continue; rtx x = pc_set (insn); @@ -3884,19 +3885,18 @@ indirect_jump_optimize (void) if (!DF_REF_IS_ARTIFICIAL (def)) { rtx_insn *def_insn = DF_REF_INSN (def); - rtx note = find_reg_note (def_insn, REG_LABEL_OPERAND, NULL_RTX); - - if (note) + rtx lab = NULL_RTX; + rtx set = single_set (def_insn); + if (set && GET_CODE (SET_SRC (set)) == LABEL_REF) + lab = SET_SRC (set); + else { - /* Substitute a LABEL_REF to the label given by the - note rather than using SET_SRC of DEF_INSN. - DEF_INSN might be loading the label constant from - a constant pool, which isn't what we want in a - direct branch. */ - rtx lab = gen_rtx_LABEL_REF (Pmode, XEXP (note, 0)); - if (validate_replace_rtx (SET_SRC (x), lab, insn)) - rebuild_p = true; + rtx eqnote = find_reg_note (def_insn, REG_EQUAL, NULL_RTX); + if (eqnote && GET_CODE (XEXP (eqnote, 0)) == LABEL_REF) + lab = XEXP (eqnote, 0); } + if (lab && validate_replace_rtx (SET_SRC (x), lab, insn)) + rebuild_p = true; } } } --- gcc/testsuite/gcc.c-torture/execute/pr70460.c.jj 2016-03-30 19:08:39.295335567 +0200 +++ gcc/testsuite/gcc.c-torture/execute/pr70460.c 2016-03-30 19:08:18.000000000 +0200 @@ -0,0 +1,29 @@ +/* PR rtl-optimization/70460 */ + +int c; + +__attribute__((noinline, noclone)) void +foo (int x) +{ + static int b[] = { &&lab1 - &&lab0, &&lab2 - &&lab0 }; + void *a = &&lab0 + b[x]; + goto *a; +lab1: + c += 2; +lab2: + c++; +lab0: + ; +} + +int +main () +{ + foo (0); + if (c != 3) + __builtin_abort (); + foo (1); + if (c != 4) + __builtin_abort (); + return 0; +} Jakub