X-Git-Url: https://oss.titaniummirror.com/gitweb?a=blobdiff_plain;f=gcc%2Fcombine-stack-adj.c;fp=gcc%2Fcombine-stack-adj.c;h=c678a607c660184f8f2872de9f0d2539b78b6678;hb=6fed43773c9b0ce596dca5686f37ac3fc0fa11c0;hp=0000000000000000000000000000000000000000;hpb=27b11d56b743098deb193d510b337ba22dc52e5c;p=msp430-gcc.git diff --git a/gcc/combine-stack-adj.c b/gcc/combine-stack-adj.c new file mode 100644 index 00000000..c678a607 --- /dev/null +++ b/gcc/combine-stack-adj.c @@ -0,0 +1,564 @@ +/* Combine stack adjustments. + Copyright (C) 1987, 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, + 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008 + 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 +. */ + +/* 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sub/mov pair due to restrictions in calls.c. + + Propagation stops when any of the insns that need adjusting are + (a) no longer valid because we've exceeded their range, (b) a + non-trivial push instruction, or (c) a call instruction.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 "output.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 "toplev.h" +#include "reload.h" +#include "timevar.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 stack memory references between stack adjusting + instructions. */ + +struct csa_memlist +{ + HOST_WIDE_INT sp_offset; + rtx insn, *mem; + struct csa_memlist *next; +}; + +static int stack_memref_p (rtx); +static rtx single_set_for_csa (rtx); +static void free_csa_memlist (struct csa_memlist *); +static struct csa_memlist *record_one_stack_memref (rtx, rtx *, + struct csa_memlist *); +static int try_apply_stack_adjustment (rtx, struct csa_memlist *, + HOST_WIDE_INT, HOST_WIDE_INT); +static void combine_stack_adjustments_for_block (basic_block); +static int record_stack_memrefs (rtx *, void *); + + +/* Main entry point for stack adjustment combination. */ + +static void +combine_stack_adjustments (void) +{ + basic_block bb; + + FOR_EACH_BB (bb) + 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 + && GET_CODE (XEXP (x, 1)) == CONST_INT) + 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_memlist nodes. */ + +static void +free_csa_memlist (struct csa_memlist *memlist) +{ + struct csa_memlist *next; + for (; memlist ; memlist = next) + { + next = memlist->next; + free (memlist); + } +} + +/* Create a new csa_memlist node from the given memory reference. + It is already known that the memory is stack_memref_p. */ + +static struct csa_memlist * +record_one_stack_memref (rtx insn, rtx *mem, struct csa_memlist *next_memlist) +{ + struct csa_memlist *ml; + + ml = XNEW (struct csa_memlist); + + if (XEXP (*mem, 0) == stack_pointer_rtx) + ml->sp_offset = 0; + else + ml->sp_offset = INTVAL (XEXP (XEXP (*mem, 0), 1)); + + ml->insn = insn; + ml->mem = mem; + ml->next = next_memlist; + + return ml; +} + +/* Attempt to apply ADJUST to the stack adjusting insn INSN, as well + as each of the memories in MEMLIST. Return true on success. */ + +static int +try_apply_stack_adjustment (rtx insn, struct csa_memlist *memlist, HOST_WIDE_INT new_adjust, + HOST_WIDE_INT delta) +{ + struct csa_memlist *ml; + rtx set; + + set = single_set_for_csa (insn); + validate_change (insn, &XEXP (SET_SRC (set), 1), GEN_INT (new_adjust), 1); + + for (ml = memlist; ml ; ml = ml->next) + validate_change + (ml->insn, ml->mem, + replace_equiv_address_nv (*ml->mem, + plus_constant (stack_pointer_rtx, + ml->sp_offset - delta)), 1); + + if (apply_change_group ()) + { + /* Succeeded. Update our knowledge of the memory references. */ + for (ml = memlist; 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 references in + the insn and discard all other stack pointer references. */ +struct record_stack_memrefs_data +{ + rtx insn; + struct csa_memlist *memlist; +}; + +static int +record_stack_memrefs (rtx *xp, void *data) +{ + rtx x = *xp; + struct record_stack_memrefs_data *d = + (struct record_stack_memrefs_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->memlist = record_one_stack_memref (d->insn, xp, d->memlist); + return -1; + } + return 1; + 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. */ + if (REGNO (x) == STACK_POINTER_REGNUM) + return 1; + break; + default: + break; + } + return 0; +} + +/* Adjust or create REG_FRAME_RELATED_EXPR note when merging a stack + adjustment into a frame related insn. */ + +static void +adjust_frame_related_expr (rtx last_sp_set, rtx insn, + HOST_WIDE_INT this_adjust) +{ + rtx note = find_reg_note (last_sp_set, REG_FRAME_RELATED_EXPR, NULL_RTX); + rtx new_expr = NULL_RTX; + + if (note == NULL_RTX && RTX_FRAME_RELATED_P (insn)) + return; + + if (note + && GET_CODE (XEXP (note, 0)) == SEQUENCE + && XVECLEN (XEXP (note, 0), 0) >= 2) + { + rtx expr = XEXP (note, 0); + rtx last = XVECEXP (expr, 0, XVECLEN (expr, 0) - 1); + int i; + + if (GET_CODE (last) == SET + && RTX_FRAME_RELATED_P (last) == RTX_FRAME_RELATED_P (insn) + && SET_DEST (last) == stack_pointer_rtx + && GET_CODE (SET_SRC (last)) == PLUS + && XEXP (SET_SRC (last), 0) == stack_pointer_rtx + && GET_CODE (XEXP (SET_SRC (last), 1)) == CONST_INT) + { + XEXP (SET_SRC (last), 1) + = GEN_INT (INTVAL (XEXP (SET_SRC (last), 1)) + this_adjust); + return; + } + + new_expr = gen_rtx_SEQUENCE (VOIDmode, + rtvec_alloc (XVECLEN (expr, 0) + 1)); + for (i = 0; i < XVECLEN (expr, 0); i++) + XVECEXP (new_expr, 0, i) = XVECEXP (expr, 0, i); + } + else + { + new_expr = gen_rtx_SEQUENCE (VOIDmode, rtvec_alloc (2)); + if (note) + XVECEXP (new_expr, 0, 0) = XEXP (note, 0); + else + { + rtx expr = copy_rtx (single_set_for_csa (last_sp_set)); + + XEXP (SET_SRC (expr), 1) + = GEN_INT (INTVAL (XEXP (SET_SRC (expr), 1)) - this_adjust); + RTX_FRAME_RELATED_P (expr) = 1; + XVECEXP (new_expr, 0, 0) = expr; + } + } + + XVECEXP (new_expr, 0, XVECLEN (new_expr, 0) - 1) + = copy_rtx (single_set_for_csa (insn)); + RTX_FRAME_RELATED_P (XVECEXP (new_expr, 0, XVECLEN (new_expr, 0) - 1)) + = RTX_FRAME_RELATED_P (insn); + if (note) + XEXP (note, 0) = new_expr; + else + REG_NOTES (last_sp_set) + = gen_rtx_EXPR_LIST (REG_FRAME_RELATED_EXPR, new_expr, + REG_NOTES (last_sp_set)); +} + +/* 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; + struct csa_memlist *memlist = NULL; + rtx insn, next, set; + struct record_stack_memrefs_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 + && GET_CODE (XEXP (src, 1)) == CONST_INT) + { + 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 memrefs 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, memlist, + last_sp_adjust + this_adjust, + this_adjust)) + { + if (RTX_FRAME_RELATED_P (last_sp_set)) + adjust_frame_related_expr (last_sp_set, insn, + this_adjust); + /* It worked! */ + 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, memlist, + last_sp_adjust + this_adjust, + -last_sp_adjust)) + { + /* It worked! */ + delete_insn (last_sp_set); + last_sp_set = insn; + last_sp_adjust += this_adjust; + free_csa_memlist (memlist); + memlist = 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 && last_sp_adjust == 0) + delete_insn (last_sp_set); + free_csa_memlist (memlist); + memlist = NULL; + last_sp_set = insn; + last_sp_adjust = this_adjust; + continue; + } + + /* Find a predecrement of exactly the previous adjustment and + turn it into a direct store. Obviously we can't do this if + there were any intervening uses of the stack pointer. */ + if (memlist == NULL + && MEM_P (dest) + && ((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_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) + && validate_change (insn, &SET_DEST (set), + replace_equiv_address (dest, + stack_pointer_rtx), + 0)) + { + delete_insn (last_sp_set); + free_csa_memlist (memlist); + memlist = NULL; + last_sp_set = NULL_RTX; + last_sp_adjust = 0; + continue; + } + } + + data.insn = insn; + data.memlist = memlist; + if (!CALL_P (insn) && last_sp_set + && !for_each_rtx (&PATTERN (insn), record_stack_memrefs, &data)) + { + memlist = data.memlist; + continue; + } + memlist = data.memlist; + + /* 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) + delete_insn (last_sp_set); + free_csa_memlist (memlist); + memlist = NULL; + last_sp_set = NULL_RTX; + last_sp_adjust = 0; + } + } + + if (last_sp_set && last_sp_adjust == 0) + delete_insn (last_sp_set); + + if (memlist) + free_csa_memlist (memlist); +} + + +static bool +gate_handle_stack_adjustments (void) +{ + return (optimize > 0); +} + +static unsigned int +rest_of_handle_stack_adjustments (void) +{ + cleanup_cfg (flag_crossjumping ? CLEANUP_CROSSJUMP : 0); + + /* This is kind of a heuristic. We need to run combine_stack_adjustments + even for machines with possibly nonzero 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) +#endif + { + df_note_add_problem (); + df_analyze (); + combine_stack_adjustments (); + } + return 0; +} + +struct rtl_opt_pass pass_stack_adjustments = +{ + { + RTL_PASS, + "csa", /* name */ + gate_handle_stack_adjustments, /* gate */ + rest_of_handle_stack_adjustments, /* execute */ + NULL, /* sub */ + NULL, /* next */ + 0, /* static_pass_number */ + 0, /* tv_id */ + 0, /* properties_required */ + 0, /* properties_provided */ + 0, /* properties_destroyed */ + 0, /* todo_flags_start */ + TODO_df_finish | TODO_verify_rtl_sharing | + TODO_dump_func | + TODO_ggc_collect, /* todo_flags_finish */ + } +}; +