From 1bc5aee63eb72b341f506ad058502cd0361f0d10 Mon Sep 17 00:00:00 2001 From: Ben Cheng Date: Tue, 25 Mar 2014 22:37:19 -0700 Subject: Initial checkin of GCC 4.9.0 from trunk (r208799). Change-Id: I48a3c08bb98542aa215912a75f03c0890e497dba --- gcc-4.9/gcc/dce.c | 1258 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 1258 insertions(+) create mode 100644 gcc-4.9/gcc/dce.c (limited to 'gcc-4.9/gcc/dce.c') diff --git a/gcc-4.9/gcc/dce.c b/gcc-4.9/gcc/dce.c new file mode 100644 index 000000000..07592f46a --- /dev/null +++ b/gcc-4.9/gcc/dce.c @@ -0,0 +1,1258 @@ +/* RTL dead code elimination. + Copyright (C) 2005-2014 Free Software Foundation, Inc. + +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 +. */ + +#include "config.h" +#include "system.h" +#include "coretypes.h" +#include "hashtab.h" +#include "tm.h" +#include "rtl.h" +#include "tree.h" +#include "regs.h" +#include "hard-reg-set.h" +#include "flags.h" +#include "except.h" +#include "df.h" +#include "cselib.h" +#include "dce.h" +#include "valtrack.h" +#include "tree-pass.h" +#include "dbgcnt.h" +#include "tm_p.h" +#include "emit-rtl.h" /* FIXME: Can go away once crtl is moved to rtl.h. */ + + +/* ------------------------------------------------------------------------- + Core mark/delete routines + ------------------------------------------------------------------------- */ + +/* True if we are invoked while the df engine is running; in this case, + we don't want to reenter it. */ +static bool df_in_progress = false; + +/* True if we are allowed to alter the CFG in this pass. */ +static bool can_alter_cfg = false; + +/* Instructions that have been marked but whose dependencies have not + yet been processed. */ +static vec worklist; + +/* Bitmap of instructions marked as needed indexed by INSN_UID. */ +static sbitmap marked; + +/* Bitmap obstacks used for block processing by the fast algorithm. */ +static bitmap_obstack dce_blocks_bitmap_obstack; +static bitmap_obstack dce_tmp_bitmap_obstack; + +static bool find_call_stack_args (rtx, bool, bool, bitmap); + +/* A subroutine for which BODY is part of the instruction being tested; + either the top-level pattern, or an element of a PARALLEL. The + instruction is known not to be a bare USE or CLOBBER. */ + +static bool +deletable_insn_p_1 (rtx body) +{ + switch (GET_CODE (body)) + { + case PREFETCH: + case TRAP_IF: + /* The UNSPEC case was added here because the ia-64 claims that + USEs do not work after reload and generates UNSPECS rather + than USEs. Since dce is run after reload we need to avoid + deleting these even if they are dead. If it turns out that + USEs really do work after reload, the ia-64 should be + changed, and the UNSPEC case can be removed. */ + case UNSPEC: + return false; + + default: + return !volatile_refs_p (body); + } +} + + +/* Return true if INSN is a normal instruction that can be deleted by + the DCE pass. */ + +static bool +deletable_insn_p (rtx insn, bool fast, bitmap arg_stores) +{ + rtx body, x; + int i; + + if (CALL_P (insn) + /* We cannot delete calls inside of the recursive dce because + this may cause basic blocks to be deleted and this messes up + the rest of the stack of optimization passes. */ + && (!df_in_progress) + /* We cannot delete pure or const sibling calls because it is + hard to see the result. */ + && (!SIBLING_CALL_P (insn)) + /* We can delete dead const or pure calls as long as they do not + infinite loop. */ + && (RTL_CONST_OR_PURE_CALL_P (insn) + && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn))) + return find_call_stack_args (insn, false, fast, arg_stores); + + /* Don't delete jumps, notes and the like. */ + if (!NONJUMP_INSN_P (insn)) + return false; + + /* Don't delete insns that may throw if we cannot do so. */ + if (!(cfun->can_delete_dead_exceptions && can_alter_cfg) + && !insn_nothrow_p (insn)) + return false; + + /* If INSN sets a global_reg, leave it untouched. */ + for (df_ref *def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++) + if (HARD_REGISTER_NUM_P (DF_REF_REGNO (*def_rec)) + && global_regs[DF_REF_REGNO (*def_rec)]) + return false; + + body = PATTERN (insn); + switch (GET_CODE (body)) + { + case USE: + case VAR_LOCATION: + return false; + + case CLOBBER: + if (fast) + { + /* A CLOBBER of a dead pseudo register serves no purpose. + That is not necessarily true for hard registers until + after reload. */ + x = XEXP (body, 0); + return REG_P (x) && (!HARD_REGISTER_P (x) || reload_completed); + } + else + /* Because of the way that use-def chains are built, it is not + possible to tell if the clobber is dead because it can + never be the target of a use-def chain. */ + return false; + + case PARALLEL: + for (i = XVECLEN (body, 0) - 1; i >= 0; i--) + if (!deletable_insn_p_1 (XVECEXP (body, 0, i))) + return false; + return true; + + default: + return deletable_insn_p_1 (body); + } +} + + +/* Return true if INSN has been marked as needed. */ + +static inline int +marked_insn_p (rtx insn) +{ + /* Artificial defs are always needed and they do not have an insn. + We should never see them here. */ + gcc_assert (insn); + return bitmap_bit_p (marked, INSN_UID (insn)); +} + + +/* If INSN has not yet been marked as needed, mark it now, and add it to + the worklist. */ + +static void +mark_insn (rtx insn, bool fast) +{ + if (!marked_insn_p (insn)) + { + if (!fast) + worklist.safe_push (insn); + bitmap_set_bit (marked, INSN_UID (insn)); + if (dump_file) + fprintf (dump_file, " Adding insn %d to worklist\n", INSN_UID (insn)); + if (CALL_P (insn) + && !df_in_progress + && !SIBLING_CALL_P (insn) + && (RTL_CONST_OR_PURE_CALL_P (insn) + && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn))) + find_call_stack_args (insn, true, fast, NULL); + } +} + + +/* A note_stores callback used by mark_nonreg_stores. DATA is the + instruction containing DEST. */ + +static void +mark_nonreg_stores_1 (rtx dest, const_rtx pattern, void *data) +{ + if (GET_CODE (pattern) != CLOBBER && !REG_P (dest)) + mark_insn ((rtx) data, true); +} + + +/* A note_stores callback used by mark_nonreg_stores. DATA is the + instruction containing DEST. */ + +static void +mark_nonreg_stores_2 (rtx dest, const_rtx pattern, void *data) +{ + if (GET_CODE (pattern) != CLOBBER && !REG_P (dest)) + mark_insn ((rtx) data, false); +} + + +/* Mark INSN if BODY stores to a non-register destination. */ + +static void +mark_nonreg_stores (rtx body, rtx insn, bool fast) +{ + if (fast) + note_stores (body, mark_nonreg_stores_1, insn); + else + note_stores (body, mark_nonreg_stores_2, insn); +} + + +/* Return true if store to MEM, starting OFF bytes from stack pointer, + is a call argument store, and clear corresponding bits from SP_BYTES + bitmap if it is. */ + +static bool +check_argument_store (rtx mem, HOST_WIDE_INT off, HOST_WIDE_INT min_sp_off, + HOST_WIDE_INT max_sp_off, bitmap sp_bytes) +{ + HOST_WIDE_INT byte; + for (byte = off; byte < off + GET_MODE_SIZE (GET_MODE (mem)); byte++) + { + if (byte < min_sp_off + || byte >= max_sp_off + || !bitmap_clear_bit (sp_bytes, byte - min_sp_off)) + return false; + } + return true; +} + + +/* Try to find all stack stores of CALL_INSN arguments if + ACCUMULATE_OUTGOING_ARGS. If all stack stores have been found + and it is therefore safe to eliminate the call, return true, + otherwise return false. This function should be first called + with DO_MARK false, and only when the CALL_INSN is actually + going to be marked called again with DO_MARK true. */ + +static bool +find_call_stack_args (rtx call_insn, bool do_mark, bool fast, + bitmap arg_stores) +{ + rtx p, insn, prev_insn; + bool ret; + HOST_WIDE_INT min_sp_off, max_sp_off; + bitmap sp_bytes; + + gcc_assert (CALL_P (call_insn)); + if (!ACCUMULATE_OUTGOING_ARGS) + return true; + + if (!do_mark) + { + gcc_assert (arg_stores); + bitmap_clear (arg_stores); + } + + min_sp_off = INTTYPE_MAXIMUM (HOST_WIDE_INT); + max_sp_off = 0; + + /* First determine the minimum and maximum offset from sp for + stored arguments. */ + for (p = CALL_INSN_FUNCTION_USAGE (call_insn); p; p = XEXP (p, 1)) + if (GET_CODE (XEXP (p, 0)) == USE + && MEM_P (XEXP (XEXP (p, 0), 0))) + { + rtx mem = XEXP (XEXP (p, 0), 0), addr; + HOST_WIDE_INT off = 0, size; + if (!MEM_SIZE_KNOWN_P (mem)) + return false; + size = MEM_SIZE (mem); + addr = XEXP (mem, 0); + if (GET_CODE (addr) == PLUS + && REG_P (XEXP (addr, 0)) + && CONST_INT_P (XEXP (addr, 1))) + { + off = INTVAL (XEXP (addr, 1)); + addr = XEXP (addr, 0); + } + if (addr != stack_pointer_rtx) + { + if (!REG_P (addr)) + return false; + /* If not fast, use chains to see if addr wasn't set to + sp + offset. */ + if (!fast) + { + df_ref *use_rec; + struct df_link *defs; + rtx set; + + for (use_rec = DF_INSN_USES (call_insn); *use_rec; use_rec++) + if (rtx_equal_p (addr, DF_REF_REG (*use_rec))) + break; + + if (*use_rec == NULL) + return false; + + for (defs = DF_REF_CHAIN (*use_rec); defs; defs = defs->next) + if (! DF_REF_IS_ARTIFICIAL (defs->ref)) + break; + + if (defs == NULL) + return false; + + set = single_set (DF_REF_INSN (defs->ref)); + if (!set) + return false; + + if (GET_CODE (SET_SRC (set)) != PLUS + || XEXP (SET_SRC (set), 0) != stack_pointer_rtx + || !CONST_INT_P (XEXP (SET_SRC (set), 1))) + return false; + + off += INTVAL (XEXP (SET_SRC (set), 1)); + } + else + return false; + } + min_sp_off = MIN (min_sp_off, off); + max_sp_off = MAX (max_sp_off, off + size); + } + + if (min_sp_off >= max_sp_off) + return true; + sp_bytes = BITMAP_ALLOC (NULL); + + /* Set bits in SP_BYTES bitmap for bytes relative to sp + min_sp_off + which contain arguments. Checking has been done in the previous + loop. */ + for (p = CALL_INSN_FUNCTION_USAGE (call_insn); p; p = XEXP (p, 1)) + if (GET_CODE (XEXP (p, 0)) == USE + && MEM_P (XEXP (XEXP (p, 0), 0))) + { + rtx mem = XEXP (XEXP (p, 0), 0), addr; + HOST_WIDE_INT off = 0, byte; + addr = XEXP (mem, 0); + if (GET_CODE (addr) == PLUS + && REG_P (XEXP (addr, 0)) + && CONST_INT_P (XEXP (addr, 1))) + { + off = INTVAL (XEXP (addr, 1)); + addr = XEXP (addr, 0); + } + if (addr != stack_pointer_rtx) + { + df_ref *use_rec; + struct df_link *defs; + rtx set; + + for (use_rec = DF_INSN_USES (call_insn); *use_rec; use_rec++) + if (rtx_equal_p (addr, DF_REF_REG (*use_rec))) + break; + + for (defs = DF_REF_CHAIN (*use_rec); defs; defs = defs->next) + if (! DF_REF_IS_ARTIFICIAL (defs->ref)) + break; + + set = single_set (DF_REF_INSN (defs->ref)); + off += INTVAL (XEXP (SET_SRC (set), 1)); + } + for (byte = off; byte < off + MEM_SIZE (mem); byte++) + { + if (!bitmap_set_bit (sp_bytes, byte - min_sp_off)) + gcc_unreachable (); + } + } + + /* Walk backwards, looking for argument stores. The search stops + when seeing another call, sp adjustment or memory store other than + argument store. */ + ret = false; + for (insn = PREV_INSN (call_insn); insn; insn = prev_insn) + { + rtx set, mem, addr; + HOST_WIDE_INT off; + + if (insn == BB_HEAD (BLOCK_FOR_INSN (call_insn))) + prev_insn = NULL_RTX; + else + prev_insn = PREV_INSN (insn); + + if (CALL_P (insn)) + break; + + if (!NONDEBUG_INSN_P (insn)) + continue; + + set = single_set (insn); + if (!set || SET_DEST (set) == stack_pointer_rtx) + break; + + if (!MEM_P (SET_DEST (set))) + continue; + + mem = SET_DEST (set); + addr = XEXP (mem, 0); + off = 0; + if (GET_CODE (addr) == PLUS + && REG_P (XEXP (addr, 0)) + && CONST_INT_P (XEXP (addr, 1))) + { + off = INTVAL (XEXP (addr, 1)); + addr = XEXP (addr, 0); + } + if (addr != stack_pointer_rtx) + { + if (!REG_P (addr)) + break; + if (!fast) + { + df_ref *use_rec; + struct df_link *defs; + rtx set; + + for (use_rec = DF_INSN_USES (insn); *use_rec; use_rec++) + if (rtx_equal_p (addr, DF_REF_REG (*use_rec))) + break; + + if (*use_rec == NULL) + break; + + for (defs = DF_REF_CHAIN (*use_rec); defs; defs = defs->next) + if (! DF_REF_IS_ARTIFICIAL (defs->ref)) + break; + + if (defs == NULL) + break; + + set = single_set (DF_REF_INSN (defs->ref)); + if (!set) + break; + + if (GET_CODE (SET_SRC (set)) != PLUS + || XEXP (SET_SRC (set), 0) != stack_pointer_rtx + || !CONST_INT_P (XEXP (SET_SRC (set), 1))) + break; + + off += INTVAL (XEXP (SET_SRC (set), 1)); + } + else + break; + } + + if (GET_MODE_SIZE (GET_MODE (mem)) == 0 + || !check_argument_store (mem, off, min_sp_off, + max_sp_off, sp_bytes)) + break; + + if (!deletable_insn_p (insn, fast, NULL)) + break; + + if (do_mark) + mark_insn (insn, fast); + else + bitmap_set_bit (arg_stores, INSN_UID (insn)); + + if (bitmap_empty_p (sp_bytes)) + { + ret = true; + break; + } + } + + BITMAP_FREE (sp_bytes); + if (!ret && arg_stores) + bitmap_clear (arg_stores); + + return ret; +} + + +/* Remove all REG_EQUAL and REG_EQUIV notes referring to the registers INSN + writes to. */ + +static void +remove_reg_equal_equiv_notes_for_defs (rtx insn) +{ + df_ref *def_rec; + + for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++) + remove_reg_equal_equiv_notes_for_regno (DF_REF_REGNO (*def_rec)); +} + +/* Scan all BBs for debug insns and reset those that reference values + defined in unmarked insns. */ + +static void +reset_unmarked_insns_debug_uses (void) +{ + basic_block bb; + rtx insn, next; + + FOR_EACH_BB_REVERSE_FN (bb, cfun) + FOR_BB_INSNS_REVERSE_SAFE (bb, insn, next) + if (DEBUG_INSN_P (insn)) + { + df_ref *use_rec; + + for (use_rec = DF_INSN_USES (insn); *use_rec; use_rec++) + { + df_ref use = *use_rec; + struct df_link *defs; + for (defs = DF_REF_CHAIN (use); defs; defs = defs->next) + { + rtx ref_insn; + if (DF_REF_IS_ARTIFICIAL (defs->ref)) + continue; + ref_insn = DF_REF_INSN (defs->ref); + if (!marked_insn_p (ref_insn)) + break; + } + if (!defs) + continue; + /* ??? FIXME could we propagate the values assigned to + each of the DEFs? */ + INSN_VAR_LOCATION_LOC (insn) = gen_rtx_UNKNOWN_VAR_LOC (); + df_insn_rescan_debug_internal (insn); + break; + } + } +} + +/* Delete every instruction that hasn't been marked. */ + +static void +delete_unmarked_insns (void) +{ + basic_block bb; + rtx insn, next; + bool must_clean = false; + + FOR_EACH_BB_REVERSE_FN (bb, cfun) + FOR_BB_INSNS_REVERSE_SAFE (bb, insn, next) + if (NONDEBUG_INSN_P (insn)) + { + /* Always delete no-op moves. */ + if (noop_move_p (insn)) + ; + + /* Otherwise rely only on the DCE algorithm. */ + else if (marked_insn_p (insn)) + continue; + + /* Beware that reaching a dbg counter limit here can result + in miscompiled file. This occurs when a group of insns + must be deleted together, typically because the kept insn + depends on the output from the deleted insn. Deleting + this insns in reverse order (both at the bb level and + when looking at the blocks) minimizes this, but does not + eliminate it, since it is possible for the using insn to + be top of a block and the producer to be at the bottom of + the block. However, in most cases this will only result + in an uninitialized use of an insn that is dead anyway. + + However, there is one rare case that will cause a + miscompile: deletion of non-looping pure and constant + calls on a machine where ACCUMULATE_OUTGOING_ARGS is true. + In this case it is possible to remove the call, but leave + the argument pushes to the stack. Because of the changes + to the stack pointer, this will almost always lead to a + miscompile. */ + if (!dbg_cnt (dce)) + continue; + + if (dump_file) + fprintf (dump_file, "DCE: Deleting insn %d\n", INSN_UID (insn)); + + /* Before we delete the insn we have to remove the REG_EQUAL notes + for the destination regs in order to avoid dangling notes. */ + remove_reg_equal_equiv_notes_for_defs (insn); + + /* If a pure or const call is deleted, this may make the cfg + have unreachable blocks. We rememeber this and call + delete_unreachable_blocks at the end. */ + if (CALL_P (insn)) + must_clean = true; + + /* Now delete the insn. */ + delete_insn_and_edges (insn); + } + + /* Deleted a pure or const call. */ + if (must_clean) + delete_unreachable_blocks (); +} + + +/* Go through the instructions and mark those whose necessity is not + dependent on inter-instruction information. Make sure all other + instructions are not marked. */ + +static void +prescan_insns_for_dce (bool fast) +{ + basic_block bb; + rtx insn, prev; + bitmap arg_stores = NULL; + + if (dump_file) + fprintf (dump_file, "Finding needed instructions:\n"); + + if (!df_in_progress && ACCUMULATE_OUTGOING_ARGS) + arg_stores = BITMAP_ALLOC (NULL); + + FOR_EACH_BB_FN (bb, cfun) + { + FOR_BB_INSNS_REVERSE_SAFE (bb, insn, prev) + if (NONDEBUG_INSN_P (insn)) + { + /* Don't mark argument stores now. They will be marked + if needed when the associated CALL is marked. */ + if (arg_stores && bitmap_bit_p (arg_stores, INSN_UID (insn))) + continue; + if (deletable_insn_p (insn, fast, arg_stores)) + mark_nonreg_stores (PATTERN (insn), insn, fast); + else + mark_insn (insn, fast); + } + /* find_call_stack_args only looks at argument stores in the + same bb. */ + if (arg_stores) + bitmap_clear (arg_stores); + } + + if (arg_stores) + BITMAP_FREE (arg_stores); + + if (dump_file) + fprintf (dump_file, "Finished finding needed instructions:\n"); +} + + +/* UD-based DSE routines. */ + +/* Mark instructions that define artificially-used registers, such as + the frame pointer and the stack pointer. */ + +static void +mark_artificial_uses (void) +{ + basic_block bb; + struct df_link *defs; + df_ref *use_rec; + + FOR_ALL_BB_FN (bb, cfun) + { + for (use_rec = df_get_artificial_uses (bb->index); + *use_rec; use_rec++) + for (defs = DF_REF_CHAIN (*use_rec); defs; defs = defs->next) + if (! DF_REF_IS_ARTIFICIAL (defs->ref)) + mark_insn (DF_REF_INSN (defs->ref), false); + } +} + + +/* Mark every instruction that defines a register value that INSN uses. */ + +static void +mark_reg_dependencies (rtx insn) +{ + struct df_link *defs; + df_ref *use_rec; + + if (DEBUG_INSN_P (insn)) + return; + + for (use_rec = DF_INSN_USES (insn); *use_rec; use_rec++) + { + df_ref use = *use_rec; + if (dump_file) + { + fprintf (dump_file, "Processing use of "); + print_simple_rtl (dump_file, DF_REF_REG (use)); + fprintf (dump_file, " in insn %d:\n", INSN_UID (insn)); + } + for (defs = DF_REF_CHAIN (use); defs; defs = defs->next) + if (! DF_REF_IS_ARTIFICIAL (defs->ref)) + mark_insn (DF_REF_INSN (defs->ref), false); + } +} + + +/* Initialize global variables for a new DCE pass. */ + +static void +init_dce (bool fast) +{ + if (!df_in_progress) + { + if (!fast) + { + df_set_flags (DF_RD_PRUNE_DEAD_DEFS); + df_chain_add_problem (DF_UD_CHAIN); + } + df_analyze (); + } + + if (dump_file) + df_dump (dump_file); + + if (fast) + { + bitmap_obstack_initialize (&dce_blocks_bitmap_obstack); + bitmap_obstack_initialize (&dce_tmp_bitmap_obstack); + can_alter_cfg = false; + } + else + can_alter_cfg = true; + + marked = sbitmap_alloc (get_max_uid () + 1); + bitmap_clear (marked); +} + + +/* Free the data allocated by init_dce. */ + +static void +fini_dce (bool fast) +{ + sbitmap_free (marked); + + if (fast) + { + bitmap_obstack_release (&dce_blocks_bitmap_obstack); + bitmap_obstack_release (&dce_tmp_bitmap_obstack); + } +} + + +/* UD-chain based DCE. */ + +static unsigned int +rest_of_handle_ud_dce (void) +{ + rtx insn; + + init_dce (false); + + prescan_insns_for_dce (false); + mark_artificial_uses (); + while (worklist.length () > 0) + { + insn = worklist.pop (); + mark_reg_dependencies (insn); + } + worklist.release (); + + if (MAY_HAVE_DEBUG_INSNS) + reset_unmarked_insns_debug_uses (); + + /* Before any insns are deleted, we must remove the chains since + they are not bidirectional. */ + df_remove_problem (df_chain); + delete_unmarked_insns (); + + fini_dce (false); + return 0; +} + + +static bool +gate_ud_dce (void) +{ + return optimize > 1 && flag_dce + && dbg_cnt (dce_ud); +} + +namespace { + +const pass_data pass_data_ud_rtl_dce = +{ + RTL_PASS, /* type */ + "ud_dce", /* name */ + OPTGROUP_NONE, /* optinfo_flags */ + true, /* has_gate */ + true, /* has_execute */ + TV_DCE, /* tv_id */ + 0, /* properties_required */ + 0, /* properties_provided */ + 0, /* properties_destroyed */ + 0, /* todo_flags_start */ + ( TODO_df_finish | TODO_verify_rtl_sharing ), /* todo_flags_finish */ +}; + +class pass_ud_rtl_dce : public rtl_opt_pass +{ +public: + pass_ud_rtl_dce (gcc::context *ctxt) + : rtl_opt_pass (pass_data_ud_rtl_dce, ctxt) + {} + + /* opt_pass methods: */ + bool gate () { return gate_ud_dce (); } + unsigned int execute () { return rest_of_handle_ud_dce (); } + +}; // class pass_ud_rtl_dce + +} // anon namespace + +rtl_opt_pass * +make_pass_ud_rtl_dce (gcc::context *ctxt) +{ + return new pass_ud_rtl_dce (ctxt); +} + + +/* ------------------------------------------------------------------------- + Fast DCE functions + ------------------------------------------------------------------------- */ + +/* Process basic block BB. Return true if the live_in set has + changed. REDO_OUT is true if the info at the bottom of the block + needs to be recalculated before starting. AU is the proper set of + artificial uses. Track global substitution of uses of dead pseudos + in debug insns using GLOBAL_DEBUG. */ + +static bool +word_dce_process_block (basic_block bb, bool redo_out, + struct dead_debug_global *global_debug) +{ + bitmap local_live = BITMAP_ALLOC (&dce_tmp_bitmap_obstack); + rtx insn; + bool block_changed; + struct dead_debug_local debug; + + if (redo_out) + { + /* Need to redo the live_out set of this block if when one of + the succs of this block has had a change in it live in + set. */ + edge e; + edge_iterator ei; + df_confluence_function_n con_fun_n = df_word_lr->problem->con_fun_n; + bitmap_clear (DF_WORD_LR_OUT (bb)); + FOR_EACH_EDGE (e, ei, bb->succs) + (*con_fun_n) (e); + } + + if (dump_file) + { + fprintf (dump_file, "processing block %d live out = ", bb->index); + df_print_word_regset (dump_file, DF_WORD_LR_OUT (bb)); + } + + bitmap_copy (local_live, DF_WORD_LR_OUT (bb)); + dead_debug_local_init (&debug, NULL, global_debug); + + FOR_BB_INSNS_REVERSE (bb, insn) + if (DEBUG_INSN_P (insn)) + { + df_ref *use_rec; + for (use_rec = DF_INSN_USES (insn); *use_rec; use_rec++) + if (DF_REF_REGNO (*use_rec) >= FIRST_PSEUDO_REGISTER + && (GET_MODE_SIZE (GET_MODE (DF_REF_REAL_REG (*use_rec))) + == 2 * UNITS_PER_WORD) + && !bitmap_bit_p (local_live, 2 * DF_REF_REGNO (*use_rec)) + && !bitmap_bit_p (local_live, 2 * DF_REF_REGNO (*use_rec) + 1)) + dead_debug_add (&debug, *use_rec, DF_REF_REGNO (*use_rec)); + } + else if (INSN_P (insn)) + { + bool any_changed; + + /* No matter if the instruction is needed or not, we remove + any regno in the defs from the live set. */ + any_changed = df_word_lr_simulate_defs (insn, local_live); + if (any_changed) + mark_insn (insn, true); + + /* On the other hand, we do not allow the dead uses to set + anything in local_live. */ + if (marked_insn_p (insn)) + df_word_lr_simulate_uses (insn, local_live); + + /* Insert debug temps for dead REGs used in subsequent debug + insns. We may have to emit a debug temp even if the insn + was marked, in case the debug use was after the point of + death. */ + if (debug.used && !bitmap_empty_p (debug.used)) + { + df_ref *def_rec; + + for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++) + dead_debug_insert_temp (&debug, DF_REF_REGNO (*def_rec), insn, + marked_insn_p (insn) + && !control_flow_insn_p (insn) + ? DEBUG_TEMP_AFTER_WITH_REG_FORCE + : DEBUG_TEMP_BEFORE_WITH_VALUE); + } + + if (dump_file) + { + fprintf (dump_file, "finished processing insn %d live out = ", + INSN_UID (insn)); + df_print_word_regset (dump_file, local_live); + } + } + + block_changed = !bitmap_equal_p (local_live, DF_WORD_LR_IN (bb)); + if (block_changed) + bitmap_copy (DF_WORD_LR_IN (bb), local_live); + + dead_debug_local_finish (&debug, NULL); + BITMAP_FREE (local_live); + return block_changed; +} + + +/* Process basic block BB. Return true if the live_in set has + changed. REDO_OUT is true if the info at the bottom of the block + needs to be recalculated before starting. AU is the proper set of + artificial uses. Track global substitution of uses of dead pseudos + in debug insns using GLOBAL_DEBUG. */ + +static bool +dce_process_block (basic_block bb, bool redo_out, bitmap au, + struct dead_debug_global *global_debug) +{ + bitmap local_live = BITMAP_ALLOC (&dce_tmp_bitmap_obstack); + rtx insn; + bool block_changed; + df_ref *def_rec; + struct dead_debug_local debug; + + if (redo_out) + { + /* Need to redo the live_out set of this block if when one of + the succs of this block has had a change in it live in + set. */ + edge e; + edge_iterator ei; + df_confluence_function_n con_fun_n = df_lr->problem->con_fun_n; + bitmap_clear (DF_LR_OUT (bb)); + FOR_EACH_EDGE (e, ei, bb->succs) + (*con_fun_n) (e); + } + + if (dump_file) + { + fprintf (dump_file, "processing block %d lr out = ", bb->index); + df_print_regset (dump_file, DF_LR_OUT (bb)); + } + + bitmap_copy (local_live, DF_LR_OUT (bb)); + + df_simulate_initialize_backwards (bb, local_live); + dead_debug_local_init (&debug, NULL, global_debug); + + FOR_BB_INSNS_REVERSE (bb, insn) + if (DEBUG_INSN_P (insn)) + { + df_ref *use_rec; + for (use_rec = DF_INSN_USES (insn); *use_rec; use_rec++) + if (!bitmap_bit_p (local_live, DF_REF_REGNO (*use_rec)) + && !bitmap_bit_p (au, DF_REF_REGNO (*use_rec))) + dead_debug_add (&debug, *use_rec, DF_REF_REGNO (*use_rec)); + } + else if (INSN_P (insn)) + { + bool needed = marked_insn_p (insn); + + /* The insn is needed if there is someone who uses the output. */ + if (!needed) + for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++) + if (bitmap_bit_p (local_live, DF_REF_REGNO (*def_rec)) + || bitmap_bit_p (au, DF_REF_REGNO (*def_rec))) + { + needed = true; + mark_insn (insn, true); + break; + } + + /* No matter if the instruction is needed or not, we remove + any regno in the defs from the live set. */ + df_simulate_defs (insn, local_live); + + /* On the other hand, we do not allow the dead uses to set + anything in local_live. */ + if (needed) + df_simulate_uses (insn, local_live); + + /* Insert debug temps for dead REGs used in subsequent debug + insns. We may have to emit a debug temp even if the insn + was marked, in case the debug use was after the point of + death. */ + if (debug.used && !bitmap_empty_p (debug.used)) + for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++) + dead_debug_insert_temp (&debug, DF_REF_REGNO (*def_rec), insn, + needed && !control_flow_insn_p (insn) + ? DEBUG_TEMP_AFTER_WITH_REG_FORCE + : DEBUG_TEMP_BEFORE_WITH_VALUE); + } + + dead_debug_local_finish (&debug, NULL); + df_simulate_finalize_backwards (bb, local_live); + + block_changed = !bitmap_equal_p (local_live, DF_LR_IN (bb)); + if (block_changed) + bitmap_copy (DF_LR_IN (bb), local_live); + + BITMAP_FREE (local_live); + return block_changed; +} + + +/* Perform fast DCE once initialization is done. If WORD_LEVEL is + true, use the word level dce, otherwise do it at the pseudo + level. */ + +static void +fast_dce (bool word_level) +{ + int *postorder = df_get_postorder (DF_BACKWARD); + int n_blocks = df_get_n_blocks (DF_BACKWARD); + /* The set of blocks that have been seen on this iteration. */ + bitmap processed = BITMAP_ALLOC (&dce_blocks_bitmap_obstack); + /* The set of blocks that need to have the out vectors reset because + the in of one of their successors has changed. */ + bitmap redo_out = BITMAP_ALLOC (&dce_blocks_bitmap_obstack); + bitmap all_blocks = BITMAP_ALLOC (&dce_blocks_bitmap_obstack); + bool global_changed = true; + + /* These regs are considered always live so if they end up dying + because of some def, we need to bring the back again. Calling + df_simulate_fixup_sets has the disadvantage of calling + bb_has_eh_pred once per insn, so we cache the information + here. */ + bitmap au = &df->regular_block_artificial_uses; + bitmap au_eh = &df->eh_block_artificial_uses; + int i; + struct dead_debug_global global_debug; + + prescan_insns_for_dce (true); + + for (i = 0; i < n_blocks; i++) + bitmap_set_bit (all_blocks, postorder[i]); + + dead_debug_global_init (&global_debug, NULL); + + while (global_changed) + { + global_changed = false; + + for (i = 0; i < n_blocks; i++) + { + int index = postorder[i]; + basic_block bb = BASIC_BLOCK_FOR_FN (cfun, index); + bool local_changed; + + if (index < NUM_FIXED_BLOCKS) + { + bitmap_set_bit (processed, index); + continue; + } + + if (word_level) + local_changed + = word_dce_process_block (bb, bitmap_bit_p (redo_out, index), + &global_debug); + else + local_changed + = dce_process_block (bb, bitmap_bit_p (redo_out, index), + bb_has_eh_pred (bb) ? au_eh : au, + &global_debug); + bitmap_set_bit (processed, index); + + if (local_changed) + { + edge e; + edge_iterator ei; + FOR_EACH_EDGE (e, ei, bb->preds) + if (bitmap_bit_p (processed, e->src->index)) + /* Be tricky about when we need to iterate the + analysis. We only have redo the analysis if the + bitmaps change at the top of a block that is the + entry to a loop. */ + global_changed = true; + else + bitmap_set_bit (redo_out, e->src->index); + } + } + + if (global_changed) + { + /* Turn off the RUN_DCE flag to prevent recursive calls to + dce. */ + int old_flag = df_clear_flags (DF_LR_RUN_DCE); + + /* So something was deleted that requires a redo. Do it on + the cheap. */ + delete_unmarked_insns (); + bitmap_clear (marked); + bitmap_clear (processed); + bitmap_clear (redo_out); + + /* We do not need to rescan any instructions. We only need + to redo the dataflow equations for the blocks that had a + change at the top of the block. Then we need to redo the + iteration. */ + if (word_level) + df_analyze_problem (df_word_lr, all_blocks, postorder, n_blocks); + else + df_analyze_problem (df_lr, all_blocks, postorder, n_blocks); + + if (old_flag & DF_LR_RUN_DCE) + df_set_flags (DF_LR_RUN_DCE); + + prescan_insns_for_dce (true); + } + } + + dead_debug_global_finish (&global_debug, NULL); + + delete_unmarked_insns (); + + BITMAP_FREE (processed); + BITMAP_FREE (redo_out); + BITMAP_FREE (all_blocks); +} + + +/* Fast register level DCE. */ + +static unsigned int +rest_of_handle_fast_dce (void) +{ + init_dce (true); + fast_dce (false); + fini_dce (true); + return 0; +} + + +/* Fast byte level DCE. */ + +void +run_word_dce (void) +{ + int old_flags; + + if (!flag_dce) + return; + + timevar_push (TV_DCE); + old_flags = df_clear_flags (DF_DEFER_INSN_RESCAN + DF_NO_INSN_RESCAN); + df_word_lr_add_problem (); + init_dce (true); + fast_dce (true); + fini_dce (true); + df_set_flags (old_flags); + timevar_pop (TV_DCE); +} + + +/* This is an internal call that is used by the df live register + problem to run fast dce as a side effect of creating the live + information. The stack is organized so that the lr problem is run, + this pass is run, which updates the live info and the df scanning + info, and then returns to allow the rest of the problems to be run. + + This can be called by elsewhere but it will not update the bit + vectors for any other problems than LR. */ + +void +run_fast_df_dce (void) +{ + if (flag_dce) + { + /* If dce is able to delete something, it has to happen + immediately. Otherwise there will be problems handling the + eq_notes. */ + int old_flags = + df_clear_flags (DF_DEFER_INSN_RESCAN + DF_NO_INSN_RESCAN); + + df_in_progress = true; + rest_of_handle_fast_dce (); + df_in_progress = false; + + df_set_flags (old_flags); + } +} + + +/* Run a fast DCE pass. */ + +void +run_fast_dce (void) +{ + if (flag_dce) + rest_of_handle_fast_dce (); +} + + +static bool +gate_fast_dce (void) +{ + return optimize > 0 && flag_dce + && dbg_cnt (dce_fast); +} + +namespace { + +const pass_data pass_data_fast_rtl_dce = +{ + RTL_PASS, /* type */ + "rtl_dce", /* name */ + OPTGROUP_NONE, /* optinfo_flags */ + true, /* has_gate */ + true, /* has_execute */ + TV_DCE, /* tv_id */ + 0, /* properties_required */ + 0, /* properties_provided */ + 0, /* properties_destroyed */ + 0, /* todo_flags_start */ + ( TODO_df_finish | TODO_verify_rtl_sharing ), /* todo_flags_finish */ +}; + +class pass_fast_rtl_dce : public rtl_opt_pass +{ +public: + pass_fast_rtl_dce (gcc::context *ctxt) + : rtl_opt_pass (pass_data_fast_rtl_dce, ctxt) + {} + + /* opt_pass methods: */ + bool gate () { return gate_fast_dce (); } + unsigned int execute () { return rest_of_handle_fast_dce (); } + +}; // class pass_fast_rtl_dce + +} // anon namespace + +rtl_opt_pass * +make_pass_fast_rtl_dce (gcc::context *ctxt) +{ + return new pass_fast_rtl_dce (ctxt); +} -- cgit v1.2.3