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Diffstat (limited to 'gcc-4.9/gcc/combine-stack-adj.c')
| -rw-r--r-- | gcc-4.9/gcc/combine-stack-adj.c | 682 |
1 files changed, 682 insertions, 0 deletions
diff --git a/gcc-4.9/gcc/combine-stack-adj.c b/gcc-4.9/gcc/combine-stack-adj.c new file mode 100644 index 000000000..69fd5ea77 --- /dev/null +++ b/gcc-4.9/gcc/combine-stack-adj.c @@ -0,0 +1,682 @@ +/* Combine stack adjustments. + Copyright (C) 1987-2014 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 +<http://www.gnu.org/licenses/>. */ + +/* Track stack adjustments and stack memory references. Attempt to + reduce the number of stack adjustments by back-propagating across + the memory references. + + This is intended primarily for use with targets that do not define + ACCUMULATE_OUTGOING_ARGS. It is of significantly more value to + targets that define PREFERRED_STACK_BOUNDARY more aligned than + STACK_BOUNDARY (e.g. x86), or if not all registers can be pushed + (e.g. x86 fp regs) which would ordinarily have to be implemented + as a sub/mov pair due to restrictions in calls.c. + + Propagation stops when any of the insns that need adjusting are + (a) no longer valid because we've exceeded their range, (b) a + non-trivial push instruction, or (c) a call instruction. + + Restriction B is based on the assumption that push instructions + are smaller or faster. If a port really wants to remove all + pushes, it should have defined ACCUMULATE_OUTGOING_ARGS. The + one exception that is made is for an add immediately followed + by a push. */ + +#include "config.h" +#include "system.h" +#include "coretypes.h" +#include "tm.h" +#include "rtl.h" +#include "tm_p.h" +#include "insn-config.h" +#include "recog.h" +#include "regs.h" +#include "hard-reg-set.h" +#include "flags.h" +#include "function.h" +#include "expr.h" +#include "basic-block.h" +#include "df.h" +#include "except.h" +#include "reload.h" +#include "tree-pass.h" + + +/* Turn STACK_GROWS_DOWNWARD into a boolean. */ +#ifdef STACK_GROWS_DOWNWARD +#undef STACK_GROWS_DOWNWARD +#define STACK_GROWS_DOWNWARD 1 +#else +#define STACK_GROWS_DOWNWARD 0 +#endif + +/* This structure records two kinds of stack references between stack + adjusting instructions: stack references in memory addresses for + regular insns and all stack references for debug insns. */ + +struct csa_reflist +{ + HOST_WIDE_INT sp_offset; + rtx insn, *ref; + struct csa_reflist *next; +}; + +static int stack_memref_p (rtx); +static rtx single_set_for_csa (rtx); +static void free_csa_reflist (struct csa_reflist *); +static struct csa_reflist *record_one_stack_ref (rtx, rtx *, + struct csa_reflist *); +static int try_apply_stack_adjustment (rtx, struct csa_reflist *, + HOST_WIDE_INT, HOST_WIDE_INT); +static void combine_stack_adjustments_for_block (basic_block); +static int record_stack_refs (rtx *, void *); + + +/* Main entry point for stack adjustment combination. */ + +static void +combine_stack_adjustments (void) +{ + basic_block bb; + + FOR_EACH_BB_FN (bb, cfun) + combine_stack_adjustments_for_block (bb); +} + +/* Recognize a MEM of the form (sp) or (plus sp const). */ + +static int +stack_memref_p (rtx x) +{ + if (!MEM_P (x)) + return 0; + x = XEXP (x, 0); + + if (x == stack_pointer_rtx) + return 1; + if (GET_CODE (x) == PLUS + && XEXP (x, 0) == stack_pointer_rtx + && CONST_INT_P (XEXP (x, 1))) + return 1; + + return 0; +} + +/* Recognize either normal single_set or the hack in i386.md for + tying fp and sp adjustments. */ + +static rtx +single_set_for_csa (rtx insn) +{ + int i; + rtx tmp = single_set (insn); + if (tmp) + return tmp; + + if (!NONJUMP_INSN_P (insn) + || GET_CODE (PATTERN (insn)) != PARALLEL) + return NULL_RTX; + + tmp = PATTERN (insn); + if (GET_CODE (XVECEXP (tmp, 0, 0)) != SET) + return NULL_RTX; + + for (i = 1; i < XVECLEN (tmp, 0); ++i) + { + rtx this_rtx = XVECEXP (tmp, 0, i); + + /* The special case is allowing a no-op set. */ + if (GET_CODE (this_rtx) == SET + && SET_SRC (this_rtx) == SET_DEST (this_rtx)) + ; + else if (GET_CODE (this_rtx) != CLOBBER + && GET_CODE (this_rtx) != USE) + return NULL_RTX; + } + + return XVECEXP (tmp, 0, 0); +} + +/* Free the list of csa_reflist nodes. */ + +static void +free_csa_reflist (struct csa_reflist *reflist) +{ + struct csa_reflist *next; + for (; reflist ; reflist = next) + { + next = reflist->next; + free (reflist); + } +} + +/* Create a new csa_reflist node from the given stack reference. + It is already known that the reference is either a MEM satisfying the + predicate stack_memref_p or a REG representing the stack pointer. */ + +static struct csa_reflist * +record_one_stack_ref (rtx insn, rtx *ref, struct csa_reflist *next_reflist) +{ + struct csa_reflist *ml; + + ml = XNEW (struct csa_reflist); + + if (REG_P (*ref) || XEXP (*ref, 0) == stack_pointer_rtx) + ml->sp_offset = 0; + else + ml->sp_offset = INTVAL (XEXP (XEXP (*ref, 0), 1)); + + ml->insn = insn; + ml->ref = ref; + ml->next = next_reflist; + + return ml; +} + +/* Attempt to apply ADJUST to the stack adjusting insn INSN, as well + as each of the memories and stack references in REFLIST. Return true + on success. */ + +static int +try_apply_stack_adjustment (rtx insn, struct csa_reflist *reflist, + HOST_WIDE_INT new_adjust, HOST_WIDE_INT delta) +{ + struct csa_reflist *ml; + rtx set; + + set = single_set_for_csa (insn); + if (MEM_P (SET_DEST (set))) + validate_change (insn, &SET_DEST (set), + replace_equiv_address (SET_DEST (set), stack_pointer_rtx), + 1); + else + validate_change (insn, &XEXP (SET_SRC (set), 1), GEN_INT (new_adjust), 1); + + for (ml = reflist; ml ; ml = ml->next) + { + rtx new_addr = plus_constant (Pmode, stack_pointer_rtx, + ml->sp_offset - delta); + rtx new_val; + + if (MEM_P (*ml->ref)) + new_val = replace_equiv_address_nv (*ml->ref, new_addr); + else if (GET_MODE (*ml->ref) == GET_MODE (stack_pointer_rtx)) + new_val = new_addr; + else + new_val = lowpart_subreg (GET_MODE (*ml->ref), new_addr, + GET_MODE (new_addr)); + validate_change (ml->insn, ml->ref, new_val, 1); + } + + if (apply_change_group ()) + { + /* Succeeded. Update our knowledge of the stack references. */ + for (ml = reflist; ml ; ml = ml->next) + ml->sp_offset -= delta; + + return 1; + } + else + return 0; +} + +/* Called via for_each_rtx and used to record all stack memory and other + references in the insn and discard all other stack pointer references. */ +struct record_stack_refs_data +{ + rtx insn; + struct csa_reflist *reflist; +}; + +static int +record_stack_refs (rtx *xp, void *data) +{ + rtx x = *xp; + struct record_stack_refs_data *d = + (struct record_stack_refs_data *) data; + if (!x) + return 0; + switch (GET_CODE (x)) + { + case MEM: + if (!reg_mentioned_p (stack_pointer_rtx, x)) + return -1; + /* We are not able to handle correctly all possible memrefs containing + stack pointer, so this check is necessary. */ + if (stack_memref_p (x)) + { + d->reflist = record_one_stack_ref (d->insn, xp, d->reflist); + return -1; + } + /* Try harder for DEBUG_INSNs, handle e.g. (mem (mem (sp + 16) + 4). */ + return !DEBUG_INSN_P (d->insn); + case REG: + /* ??? We want be able to handle non-memory stack pointer + references later. For now just discard all insns referring to + stack pointer outside mem expressions. We would probably + want to teach validate_replace to simplify expressions first. + + We can't just compare with STACK_POINTER_RTX because the + reference to the stack pointer might be in some other mode. + In particular, an explicit clobber in an asm statement will + result in a QImode clobber. + + In DEBUG_INSNs, we want to replace all occurrences, otherwise + they will cause -fcompare-debug failures. */ + if (REGNO (x) == STACK_POINTER_REGNUM) + { + if (!DEBUG_INSN_P (d->insn)) + return 1; + d->reflist = record_one_stack_ref (d->insn, xp, d->reflist); + return -1; + } + break; + default: + break; + } + return 0; +} + +/* If INSN has a REG_ARGS_SIZE note, move it to LAST. + AFTER is true iff LAST follows INSN in the instruction stream. */ + +static void +maybe_move_args_size_note (rtx last, rtx insn, bool after) +{ + rtx note, last_note; + + note = find_reg_note (insn, REG_ARGS_SIZE, NULL_RTX); + if (note == NULL) + return; + + last_note = find_reg_note (last, REG_ARGS_SIZE, NULL_RTX); + if (last_note) + { + /* The ARGS_SIZE notes are *not* cumulative. They represent an + absolute value, and the "most recent" note wins. */ + if (!after) + XEXP (last_note, 0) = XEXP (note, 0); + } + else + add_reg_note (last, REG_ARGS_SIZE, XEXP (note, 0)); +} + +/* Return the next (or previous) active insn within BB. */ + +static rtx +prev_active_insn_bb (basic_block bb, rtx insn) +{ + for (insn = PREV_INSN (insn); + insn != PREV_INSN (BB_HEAD (bb)); + insn = PREV_INSN (insn)) + if (active_insn_p (insn)) + return insn; + return NULL_RTX; +} + +static rtx +next_active_insn_bb (basic_block bb, rtx insn) +{ + for (insn = NEXT_INSN (insn); + insn != NEXT_INSN (BB_END (bb)); + insn = NEXT_INSN (insn)) + if (active_insn_p (insn)) + return insn; + return NULL_RTX; +} + +/* If INSN has a REG_ARGS_SIZE note, if possible move it to PREV. Otherwise + search for a nearby candidate within BB where we can stick the note. */ + +static void +force_move_args_size_note (basic_block bb, rtx prev, rtx insn) +{ + rtx note, test, next_candidate, prev_candidate; + + /* If PREV exists, tail-call to the logic in the other function. */ + if (prev) + { + maybe_move_args_size_note (prev, insn, false); + return; + } + + /* First, make sure there's anything that needs doing. */ + note = find_reg_note (insn, REG_ARGS_SIZE, NULL_RTX); + if (note == NULL) + return; + + /* We need to find a spot between the previous and next exception points + where we can place the note and "properly" deallocate the arguments. */ + next_candidate = prev_candidate = NULL; + + /* It is often the case that we have insns in the order: + call + add sp (previous deallocation) + sub sp (align for next arglist) + push arg + and the add/sub cancel. Therefore we begin by searching forward. */ + + test = insn; + while ((test = next_active_insn_bb (bb, test)) != NULL) + { + /* Found an existing note: nothing to do. */ + if (find_reg_note (test, REG_ARGS_SIZE, NULL_RTX)) + return; + /* Found something that affects unwinding. Stop searching. */ + if (CALL_P (test) || !insn_nothrow_p (test)) + break; + if (next_candidate == NULL) + next_candidate = test; + } + + test = insn; + while ((test = prev_active_insn_bb (bb, test)) != NULL) + { + rtx tnote; + /* Found a place that seems logical to adjust the stack. */ + tnote = find_reg_note (test, REG_ARGS_SIZE, NULL_RTX); + if (tnote) + { + XEXP (tnote, 0) = XEXP (note, 0); + return; + } + if (prev_candidate == NULL) + prev_candidate = test; + /* Found something that affects unwinding. Stop searching. */ + if (CALL_P (test) || !insn_nothrow_p (test)) + break; + } + + if (prev_candidate) + test = prev_candidate; + else if (next_candidate) + test = next_candidate; + else + { + /* ??? We *must* have a place, lest we ICE on the lost adjustment. + Options are: dummy clobber insn, nop, or prevent the removal of + the sp += 0 insn. */ + /* TODO: Find another way to indicate to the dwarf2 code that we + have not in fact lost an adjustment. */ + test = emit_insn_before (gen_rtx_CLOBBER (VOIDmode, const0_rtx), insn); + } + add_reg_note (test, REG_ARGS_SIZE, XEXP (note, 0)); +} + +/* Subroutine of combine_stack_adjustments, called for each basic block. */ + +static void +combine_stack_adjustments_for_block (basic_block bb) +{ + HOST_WIDE_INT last_sp_adjust = 0; + rtx last_sp_set = NULL_RTX; + rtx last2_sp_set = NULL_RTX; + struct csa_reflist *reflist = NULL; + rtx insn, next, set; + struct record_stack_refs_data data; + bool end_of_block = false; + + for (insn = BB_HEAD (bb); !end_of_block ; insn = next) + { + end_of_block = insn == BB_END (bb); + next = NEXT_INSN (insn); + + if (! INSN_P (insn)) + continue; + + set = single_set_for_csa (insn); + if (set) + { + rtx dest = SET_DEST (set); + rtx src = SET_SRC (set); + + /* Find constant additions to the stack pointer. */ + if (dest == stack_pointer_rtx + && GET_CODE (src) == PLUS + && XEXP (src, 0) == stack_pointer_rtx + && CONST_INT_P (XEXP (src, 1))) + { + HOST_WIDE_INT this_adjust = INTVAL (XEXP (src, 1)); + + /* If we've not seen an adjustment previously, record + it now and continue. */ + if (! last_sp_set) + { + last_sp_set = insn; + last_sp_adjust = this_adjust; + continue; + } + + /* If not all recorded refs can be adjusted, or the + adjustment is now too large for a constant addition, + we cannot merge the two stack adjustments. + + Also we need to be careful to not move stack pointer + such that we create stack accesses outside the allocated + area. We can combine an allocation into the first insn, + or a deallocation into the second insn. We can not + combine an allocation followed by a deallocation. + + The only somewhat frequent occurrence of the later is when + a function allocates a stack frame but does not use it. + For this case, we would need to analyze rtl stream to be + sure that allocated area is really unused. This means not + only checking the memory references, but also all registers + or global memory references possibly containing a stack + frame address. + + Perhaps the best way to address this problem is to teach + gcc not to allocate stack for objects never used. */ + + /* Combine an allocation into the first instruction. */ + if (STACK_GROWS_DOWNWARD ? this_adjust <= 0 : this_adjust >= 0) + { + if (try_apply_stack_adjustment (last_sp_set, reflist, + last_sp_adjust + this_adjust, + this_adjust)) + { + /* It worked! */ + maybe_move_args_size_note (last_sp_set, insn, false); + delete_insn (insn); + last_sp_adjust += this_adjust; + continue; + } + } + + /* Otherwise we have a deallocation. Do not combine with + a previous allocation. Combine into the second insn. */ + else if (STACK_GROWS_DOWNWARD + ? last_sp_adjust >= 0 : last_sp_adjust <= 0) + { + if (try_apply_stack_adjustment (insn, reflist, + last_sp_adjust + this_adjust, + -last_sp_adjust)) + { + /* It worked! */ + maybe_move_args_size_note (insn, last_sp_set, true); + delete_insn (last_sp_set); + last_sp_set = insn; + last_sp_adjust += this_adjust; + free_csa_reflist (reflist); + reflist = NULL; + continue; + } + } + + /* Combination failed. Restart processing from here. If + deallocation+allocation conspired to cancel, we can + delete the old deallocation insn. */ + if (last_sp_set) + { + if (last_sp_adjust == 0) + { + maybe_move_args_size_note (insn, last_sp_set, true); + delete_insn (last_sp_set); + } + else + last2_sp_set = last_sp_set; + } + free_csa_reflist (reflist); + reflist = NULL; + last_sp_set = insn; + last_sp_adjust = this_adjust; + continue; + } + + /* Find a store with pre-(dec|inc)rement or pre-modify of exactly + the previous adjustment and turn it into a simple store. This + is equivalent to anticipating the stack adjustment so this must + be an allocation. */ + if (MEM_P (dest) + && ((STACK_GROWS_DOWNWARD + ? (GET_CODE (XEXP (dest, 0)) == PRE_DEC + && last_sp_adjust + == (HOST_WIDE_INT) GET_MODE_SIZE (GET_MODE (dest))) + : (GET_CODE (XEXP (dest, 0)) == PRE_INC + && last_sp_adjust + == -(HOST_WIDE_INT) GET_MODE_SIZE (GET_MODE (dest)))) + || ((STACK_GROWS_DOWNWARD + ? last_sp_adjust >= 0 : last_sp_adjust <= 0) + && GET_CODE (XEXP (dest, 0)) == PRE_MODIFY + && GET_CODE (XEXP (XEXP (dest, 0), 1)) == PLUS + && XEXP (XEXP (XEXP (dest, 0), 1), 0) + == stack_pointer_rtx + && GET_CODE (XEXP (XEXP (XEXP (dest, 0), 1), 1)) + == CONST_INT + && INTVAL (XEXP (XEXP (XEXP (dest, 0), 1), 1)) + == -last_sp_adjust)) + && XEXP (XEXP (dest, 0), 0) == stack_pointer_rtx + && !reg_mentioned_p (stack_pointer_rtx, src) + && memory_address_p (GET_MODE (dest), stack_pointer_rtx) + && try_apply_stack_adjustment (insn, reflist, 0, + -last_sp_adjust)) + { + if (last2_sp_set) + maybe_move_args_size_note (last2_sp_set, last_sp_set, false); + else + maybe_move_args_size_note (insn, last_sp_set, true); + delete_insn (last_sp_set); + free_csa_reflist (reflist); + reflist = NULL; + last_sp_set = NULL_RTX; + last_sp_adjust = 0; + continue; + } + } + + data.insn = insn; + data.reflist = reflist; + if (!CALL_P (insn) && last_sp_set + && !for_each_rtx (&PATTERN (insn), record_stack_refs, &data)) + { + reflist = data.reflist; + continue; + } + reflist = data.reflist; + + /* Otherwise, we were not able to process the instruction. + Do not continue collecting data across such a one. */ + if (last_sp_set + && (CALL_P (insn) + || reg_mentioned_p (stack_pointer_rtx, PATTERN (insn)))) + { + if (last_sp_set && last_sp_adjust == 0) + { + force_move_args_size_note (bb, last2_sp_set, last_sp_set); + delete_insn (last_sp_set); + } + free_csa_reflist (reflist); + reflist = NULL; + last2_sp_set = NULL_RTX; + last_sp_set = NULL_RTX; + last_sp_adjust = 0; + } + } + + if (last_sp_set && last_sp_adjust == 0) + { + force_move_args_size_note (bb, last2_sp_set, last_sp_set); + delete_insn (last_sp_set); + } + + if (reflist) + free_csa_reflist (reflist); +} + + +static bool +gate_handle_stack_adjustments (void) +{ + /* This is kind of a heuristic. We need to run combine_stack_adjustments + even for machines with possibly nonzero TARGET_RETURN_POPS_ARGS + and ACCUMULATE_OUTGOING_ARGS. We expect that only ports having + push instructions will have popping returns. */ +#ifndef PUSH_ROUNDING + if (ACCUMULATE_OUTGOING_ARGS) + return false; +#endif + return flag_combine_stack_adjustments; +} + +static unsigned int +rest_of_handle_stack_adjustments (void) +{ + df_note_add_problem (); + df_analyze (); + combine_stack_adjustments (); + return 0; +} + +namespace { + +const pass_data pass_data_stack_adjustments = +{ + RTL_PASS, /* type */ + "csa", /* name */ + OPTGROUP_NONE, /* optinfo_flags */ + true, /* has_gate */ + true, /* has_execute */ + TV_COMBINE_STACK_ADJUST, /* 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_stack_adjustments : public rtl_opt_pass +{ +public: + pass_stack_adjustments (gcc::context *ctxt) + : rtl_opt_pass (pass_data_stack_adjustments, ctxt) + {} + + /* opt_pass methods: */ + bool gate () { return gate_handle_stack_adjustments (); } + unsigned int execute () { return rest_of_handle_stack_adjustments (); } + +}; // class pass_stack_adjustments + +} // anon namespace + +rtl_opt_pass * +make_pass_stack_adjustments (gcc::context *ctxt) +{ + return new pass_stack_adjustments (ctxt); +} |