/* Coalesce spilled pseudos. Copyright (C) 2010-2017 Free Software Foundation, Inc. Contributed by Vladimir Makarov . This file is part of GCC. GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version. GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GCC; see the file COPYING3. If not see . */ /* This file contains a pass making some simple RTL code transformations by coalescing pseudos to remove some move insns. Spilling pseudos in LRA can create memory-memory moves. We should remove potential memory-memory moves before the next constraint pass because the constraint pass will generate additional insns for such moves and all these insns will be hard to remove afterwards. Here we coalesce only spilled pseudos. Coalescing non-spilled pseudos (with different hard regs) might result in spilling additional pseudos because of possible conflicts with other non-spilled pseudos and, as a consequence, in more constraint passes and even LRA infinite cycling. Trivial the same hard register moves will be removed by subsequent compiler passes. We don't coalesce special reload pseudos. It complicates LRA code a lot without visible generated code improvement. The pseudo live-ranges are used to find conflicting pseudos during coalescing. Most frequently executed moves is tried to be coalesced first. */ #include "config.h" #include "system.h" #include "coretypes.h" #include "backend.h" #include "rtl.h" #include "predict.h" #include "df.h" #include "insn-config.h" #include "regs.h" #include "memmodel.h" #include "ira.h" #include "recog.h" #include "lra-int.h" /* Arrays whose elements represent the first and the next pseudo (regno) in the coalesced pseudos group to which given pseudo (its regno is the index) belongs. The next of the last pseudo in the group refers to the first pseudo in the group, in other words the group is represented by a cyclic list. */ static int *first_coalesced_pseudo, *next_coalesced_pseudo; /* The function is used to sort moves according to their execution frequencies. */ static int move_freq_compare_func (const void *v1p, const void *v2p) { rtx_insn *mv1 = *(rtx_insn * const *) v1p; rtx_insn *mv2 = *(rtx_insn * const *) v2p; int pri1, pri2; pri1 = REG_FREQ_FROM_BB (BLOCK_FOR_INSN (mv1)); pri2 = REG_FREQ_FROM_BB (BLOCK_FOR_INSN (mv2)); if (pri2 - pri1) return pri2 - pri1; /* If frequencies are equal, sort by moves, so that the results of qsort leave nothing to chance. */ return (int) INSN_UID (mv1) - (int) INSN_UID (mv2); } /* Pseudos which go away after coalescing. */ static bitmap_head coalesced_pseudos_bitmap; /* Merge two sets of coalesced pseudos given correspondingly by pseudos REGNO1 and REGNO2 (more accurately merging REGNO2 group into REGNO1 group). Set up COALESCED_PSEUDOS_BITMAP. */ static void merge_pseudos (int regno1, int regno2) { int regno, first, first2, last, next; first = first_coalesced_pseudo[regno1]; if ((first2 = first_coalesced_pseudo[regno2]) == first) return; for (last = regno2, regno = next_coalesced_pseudo[regno2];; regno = next_coalesced_pseudo[regno]) { first_coalesced_pseudo[regno] = first; bitmap_set_bit (&coalesced_pseudos_bitmap, regno); if (regno == regno2) break; last = regno; } next = next_coalesced_pseudo[first]; next_coalesced_pseudo[first] = regno2; next_coalesced_pseudo[last] = next; lra_reg_info[first].live_ranges = (lra_merge_live_ranges (lra_reg_info[first].live_ranges, lra_copy_live_range_list (lra_reg_info[first2].live_ranges))); if (partial_subreg_p (lra_reg_info[first].biggest_mode, lra_reg_info[first2].biggest_mode)) lra_reg_info[first].biggest_mode = lra_reg_info[first2].biggest_mode; } /* Change pseudos in *LOC on their coalescing group representatives. */ static bool substitute (rtx *loc) { int i, regno; const char *fmt; enum rtx_code code; bool res; if (*loc == NULL_RTX) return false; code = GET_CODE (*loc); if (code == REG) { regno = REGNO (*loc); if (regno < FIRST_PSEUDO_REGISTER || first_coalesced_pseudo[regno] == regno) return false; *loc = regno_reg_rtx[first_coalesced_pseudo[regno]]; return true; } res = false; fmt = GET_RTX_FORMAT (code); for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) { if (fmt[i] == 'e') { if (substitute (&XEXP (*loc, i))) res = true; } else if (fmt[i] == 'E') { int j; for (j = XVECLEN (*loc, i) - 1; j >= 0; j--) if (substitute (&XVECEXP (*loc, i, j))) res = true; } } return res; } /* Specialize "substitute" for use on an insn. This can't change the insn ptr, just the contents of the insn. */ static bool substitute_within_insn (rtx_insn *insn) { rtx loc = insn; return substitute (&loc); } /* The current iteration (1, 2, ...) of the coalescing pass. */ int lra_coalesce_iter; /* Return true if the move involving REGNO1 and REGNO2 is a potential memory-memory move. */ static bool mem_move_p (int regno1, int regno2) { return reg_renumber[regno1] < 0 && reg_renumber[regno2] < 0; } /* Pseudos used instead of the coalesced pseudos. */ static bitmap_head used_pseudos_bitmap; /* Set up USED_PSEUDOS_BITMAP, and update LR_BITMAP (a BB live info bitmap). */ static void update_live_info (bitmap lr_bitmap) { unsigned int j; bitmap_iterator bi; bitmap_clear (&used_pseudos_bitmap); EXECUTE_IF_AND_IN_BITMAP (&coalesced_pseudos_bitmap, lr_bitmap, FIRST_PSEUDO_REGISTER, j, bi) bitmap_set_bit (&used_pseudos_bitmap, first_coalesced_pseudo[j]); if (! bitmap_empty_p (&used_pseudos_bitmap)) { bitmap_and_compl_into (lr_bitmap, &coalesced_pseudos_bitmap); bitmap_ior_into (lr_bitmap, &used_pseudos_bitmap); } } /* Return true if pseudo REGNO can be potentially coalesced. */ static bool coalescable_pseudo_p (int regno) { lra_assert (regno >= FIRST_PSEUDO_REGISTER); return (/* We don't want to coalesce regnos with equivalences, at least without updating this info. */ ira_reg_equiv[regno].constant == NULL_RTX && ira_reg_equiv[regno].memory == NULL_RTX && ira_reg_equiv[regno].invariant == NULL_RTX); } /* The major function for aggressive pseudo coalescing of moves only if the both pseudos were spilled and not special reload pseudos. */ bool lra_coalesce (void) { basic_block bb; rtx_insn *mv, *insn, *next, **sorted_moves; rtx set; int i, mv_num, sregno, dregno; int coalesced_moves; int max_regno = max_reg_num (); bitmap_head involved_insns_bitmap; timevar_push (TV_LRA_COALESCE); if (lra_dump_file != NULL) fprintf (lra_dump_file, "\n********** Pseudos coalescing #%d: **********\n\n", ++lra_coalesce_iter); first_coalesced_pseudo = XNEWVEC (int, max_regno); next_coalesced_pseudo = XNEWVEC (int, max_regno); for (i = 0; i < max_regno; i++) first_coalesced_pseudo[i] = next_coalesced_pseudo[i] = i; sorted_moves = XNEWVEC (rtx_insn *, get_max_uid ()); mv_num = 0; /* Collect moves. */ coalesced_moves = 0; FOR_EACH_BB_FN (bb, cfun) { FOR_BB_INSNS_SAFE (bb, insn, next) if (INSN_P (insn) && (set = single_set (insn)) != NULL_RTX && REG_P (SET_DEST (set)) && REG_P (SET_SRC (set)) && (sregno = REGNO (SET_SRC (set))) >= FIRST_PSEUDO_REGISTER && (dregno = REGNO (SET_DEST (set))) >= FIRST_PSEUDO_REGISTER && mem_move_p (sregno, dregno) && coalescable_pseudo_p (sregno) && coalescable_pseudo_p (dregno) && ! side_effects_p (set) && !(lra_intersected_live_ranges_p (lra_reg_info[sregno].live_ranges, lra_reg_info[dregno].live_ranges))) sorted_moves[mv_num++] = insn; } qsort (sorted_moves, mv_num, sizeof (rtx), move_freq_compare_func); /* Coalesced copies, most frequently executed first. */ bitmap_initialize (&coalesced_pseudos_bitmap, ®_obstack); bitmap_initialize (&involved_insns_bitmap, ®_obstack); for (i = 0; i < mv_num; i++) { mv = sorted_moves[i]; set = single_set (mv); lra_assert (set != NULL && REG_P (SET_SRC (set)) && REG_P (SET_DEST (set))); sregno = REGNO (SET_SRC (set)); dregno = REGNO (SET_DEST (set)); if (first_coalesced_pseudo[sregno] == first_coalesced_pseudo[dregno]) { coalesced_moves++; if (lra_dump_file != NULL) fprintf (lra_dump_file, " Coalescing move %i:r%d-r%d (freq=%d)\n", INSN_UID (mv), sregno, dregno, REG_FREQ_FROM_BB (BLOCK_FOR_INSN (mv))); /* We updated involved_insns_bitmap when doing the merge. */ } else if (!(lra_intersected_live_ranges_p (lra_reg_info[first_coalesced_pseudo[sregno]].live_ranges, lra_reg_info[first_coalesced_pseudo[dregno]].live_ranges))) { coalesced_moves++; if (lra_dump_file != NULL) fprintf (lra_dump_file, " Coalescing move %i:r%d(%d)-r%d(%d) (freq=%d)\n", INSN_UID (mv), sregno, ORIGINAL_REGNO (SET_SRC (set)), dregno, ORIGINAL_REGNO (SET_DEST (set)), REG_FREQ_FROM_BB (BLOCK_FOR_INSN (mv))); bitmap_ior_into (&involved_insns_bitmap, &lra_reg_info[sregno].insn_bitmap); bitmap_ior_into (&involved_insns_bitmap, &lra_reg_info[dregno].insn_bitmap); merge_pseudos (sregno, dregno); } } bitmap_initialize (&used_pseudos_bitmap, ®_obstack); FOR_EACH_BB_FN (bb, cfun) { update_live_info (df_get_live_in (bb)); update_live_info (df_get_live_out (bb)); FOR_BB_INSNS_SAFE (bb, insn, next) if (INSN_P (insn) && bitmap_bit_p (&involved_insns_bitmap, INSN_UID (insn))) { if (! substitute_within_insn (insn)) continue; lra_update_insn_regno_info (insn); if ((set = single_set (insn)) != NULL_RTX && set_noop_p (set)) { /* Coalesced move. */ if (lra_dump_file != NULL) fprintf (lra_dump_file, " Removing move %i (freq=%d)\n", INSN_UID (insn), REG_FREQ_FROM_BB (BLOCK_FOR_INSN (insn))); lra_set_insn_deleted (insn); } } } /* If we have situation after inheritance pass: r1 <- p1 insn originally setting p1 i1 <- r1 setting inheritance i1 from reload r1 ... ... <- ... p2 ... dead p2 .. p1 <- i1 r2 <- i1 ...<- ... r2 ... And we are coalescing p1 and p2 using p1. In this case i1 and p1 should have different values, otherwise they can get the same hard reg and this is wrong for insn using p2 before coalescing. The situation even can be more complicated when new reload pseudos occur after the inheriatnce. So invalidate the result pseudos. */ for (i = 0; i < max_regno; i++) if (first_coalesced_pseudo[i] == i && first_coalesced_pseudo[i] != next_coalesced_pseudo[i]) { lra_set_regno_unique_value (i); if (lra_dump_file != NULL) fprintf (lra_dump_file, " Make unique value for coalescing result r%d\n", i); } bitmap_clear (&used_pseudos_bitmap); bitmap_clear (&involved_insns_bitmap); bitmap_clear (&coalesced_pseudos_bitmap); if (lra_dump_file != NULL && coalesced_moves != 0) fprintf (lra_dump_file, "Coalesced Moves = %d\n", coalesced_moves); free (sorted_moves); free (next_coalesced_pseudo); free (first_coalesced_pseudo); timevar_pop (TV_LRA_COALESCE); return coalesced_moves != 0; }