From 384d7a5522426eddc7cb7b04a65af0f397133ab9 Mon Sep 17 00:00:00 2001 From: Steven Bosscher Date: Mon, 4 Apr 2011 18:24:50 +0000 Subject: [PATCH] cprop.c (implicit_set_cond_p): Assume nothing about COND... * cprop.c (implicit_set_cond_p): Assume nothing about COND, move checks on form of COND from find_implicit_sets to here. (find_implicit_sets): Cleanup control flow. Split critical edges if it exposes implicit sets. Allocate/resize implicit_sets as necessary. (one_cprop_pass): Only delete unreachable blocks if local_cprop_pass changed something. Run df_analyze after find_implicit_sets if any edges were split. Do not allocate implicit_sets here. From-SVN: r171946 --- gcc/ChangeLog | 9 ++++ gcc/cprop.c | 142 +++++++++++++++++++++++++++++++++----------------- 2 files changed, 103 insertions(+), 48 deletions(-) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index aa99741384a..1c27c175480 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,5 +1,14 @@ 2011-04-04 Steven Bosscher + * cprop.c (implicit_set_cond_p): Assume nothing about COND, move + checks on form of COND from find_implicit_sets to here. + (find_implicit_sets): Cleanup control flow. Split critical edges + if it exposes implicit sets. Allocate/resize implicit_sets as + necessary. + (one_cprop_pass): Only delete unreachable blocks if local_cprop_pass + changed something. Run df_analyze after find_implicit_sets if any + edges were split. Do not allocate implicit_sets here. + * cprop.c: s/gcse/cprop/ everywhere except for flag_gcse. (gcse_obstack): Renamed to cprop_obstack. (GNEW, GNEWVEC, GNEWVAR): Remove. diff --git a/gcc/cprop.c b/gcc/cprop.c index 3f38be35da0..340d2356eeb 100644 --- a/gcc/cprop.c +++ b/gcc/cprop.c @@ -1343,14 +1343,27 @@ fis_get_condition (rtx jump) return get_condition (jump, NULL, false, true); } -/* Check the comparison COND to see if we can safely form an implicit set from - it. COND is either an EQ or NE comparison. */ +/* Check the comparison COND to see if we can safely form an implicit + set from it. */ static bool implicit_set_cond_p (const_rtx cond) { - const enum machine_mode mode = GET_MODE (XEXP (cond, 0)); - const_rtx cst = XEXP (cond, 1); + enum machine_mode mode; + rtx cst; + + /* COND must be either an EQ or NE comparison. */ + if (GET_CODE (cond) != EQ && GET_CODE (cond) != NE) + return false; + + /* The first operand of COND must be a pseudo-reg. */ + if (! REG_P (XEXP (cond, 0)) + || HARD_REGISTER_P (XEXP (cond, 0))) + return false; + + /* The second operand of COND must be a suitable constant. */ + mode = GET_MODE (XEXP (cond, 0)); + cst = XEXP (cond, 1); /* We can't perform this optimization if either operand might be or might contain a signed zero. */ @@ -1382,55 +1395,78 @@ implicit_set_cond_p (const_rtx cond) function records the set patterns that are implicit at the start of each basic block. - FIXME: This would be more effective if critical edges are pre-split. As - it is now, we can't record implicit sets for blocks that have - critical successor edges. This results in missed optimizations - and in more (unnecessary) work in cfgcleanup.c:thread_jump(). */ + If an implicit set is found but the set is implicit on a critical edge, + this critical edge is split. -static void + Return true if the CFG was modified, false otherwise. */ + +static bool find_implicit_sets (void) { basic_block bb, dest; - unsigned int count; rtx cond, new_rtx; + unsigned int count = 0; + bool edges_split = false; + size_t implicit_sets_size = last_basic_block + 10; + + implicit_sets = XCNEWVEC (rtx, implicit_sets_size); - count = 0; FOR_EACH_BB (bb) - /* Check for more than one successor. */ - if (EDGE_COUNT (bb->succs) > 1) - { - cond = fis_get_condition (BB_END (bb)); + { + /* Check for more than one successor. */ + if (! EDGE_COUNT (bb->succs) > 1) + continue; - if (cond - && (GET_CODE (cond) == EQ || GET_CODE (cond) == NE) - && REG_P (XEXP (cond, 0)) - && REGNO (XEXP (cond, 0)) >= FIRST_PSEUDO_REGISTER - && implicit_set_cond_p (cond)) - { - dest = GET_CODE (cond) == EQ ? BRANCH_EDGE (bb)->dest - : FALLTHRU_EDGE (bb)->dest; + cond = fis_get_condition (BB_END (bb)); - if (dest - /* Record nothing for a critical edge. */ - && single_pred_p (dest) - && dest != EXIT_BLOCK_PTR) - { - new_rtx = gen_rtx_SET (VOIDmode, XEXP (cond, 0), - XEXP (cond, 1)); - implicit_sets[dest->index] = new_rtx; - if (dump_file) - { - fprintf(dump_file, "Implicit set of reg %d in ", - REGNO (XEXP (cond, 0))); - fprintf(dump_file, "basic block %d\n", dest->index); - } - count++; - } - } + /* If no condition is found or if it isn't of a suitable form, + ignore it. */ + if (! cond || ! implicit_set_cond_p (cond)) + continue; + + dest = GET_CODE (cond) == EQ + ? BRANCH_EDGE (bb)->dest : FALLTHRU_EDGE (bb)->dest; + + /* If DEST doesn't go anywhere, ignore it. */ + if (! dest || dest == EXIT_BLOCK_PTR) + continue; + + /* We have found a suitable implicit set. Try to record it now as + a SET in DEST. If DEST has more than one predecessor, the edge + between BB and DEST is a critical edge and we must split it, + because we can only record one implicit set per DEST basic block. */ + if (! single_pred_p (dest)) + { + dest = split_edge (find_edge (bb, dest)); + edges_split = true; + } + + if (implicit_sets_size <= (size_t) dest->index) + { + size_t old_implicit_sets_size = implicit_sets_size; + implicit_sets_size *= 2; + implicit_sets = XRESIZEVEC (rtx, implicit_sets, implicit_sets_size); + memset (implicit_sets + old_implicit_sets_size, 0, + (implicit_sets_size - old_implicit_sets_size) * sizeof (rtx)); } + new_rtx = gen_rtx_SET (VOIDmode, XEXP (cond, 0), + XEXP (cond, 1)); + implicit_sets[dest->index] = new_rtx; + if (dump_file) + { + fprintf(dump_file, "Implicit set of reg %d in ", + REGNO (XEXP (cond, 0))); + fprintf(dump_file, "basic block %d\n", dest->index); + } + count++; + } + if (dump_file) fprintf (dump_file, "Found %d implicit sets\n", count); + + /* Confess our sins. */ + return edges_split; } /* Bypass conditional jumps. */ @@ -1797,14 +1833,24 @@ one_cprop_pass (void) the solver implemented in this file. */ changed |= local_cprop_pass (); if (changed) - { - delete_unreachable_blocks (); - df_analyze (); - } - - /* Determine implicit sets. */ - implicit_sets = XCNEWVEC (rtx, last_basic_block); - find_implicit_sets (); + delete_unreachable_blocks (); + + /* Determine implicit sets. This may change the CFG (split critical + edges if that exposes an implicit set). + Note that find_implicit_sets() does not rely on up-to-date DF caches + so that we do not have to re-run df_analyze() even if local CPROP + changed something. + ??? This could run earlier so that any uncovered implicit sets + sets could be exploited in local_cprop_pass() also. Later. */ + changed |= find_implicit_sets (); + + /* If local_cprop_pass() or find_implicit_sets() changed something, + run df_analyze() to bring all insn caches up-to-date, and to take + new basic blocks from edge splitting on the DF radar. + NB: This also runs the fast DCE pass, because execute_rtl_cprop + sets DF_LR_RUN_DCE. */ + if (changed) + df_analyze (); alloc_hash_table (&set_hash_table); compute_hash_table (&set_hash_table); -- 2.30.2