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Diffstat (limited to 'gcc-4.8.3/gcc/cfgbuild.c')
| -rw-r--r-- | gcc-4.8.3/gcc/cfgbuild.c | 651 |
1 files changed, 651 insertions, 0 deletions
diff --git a/gcc-4.8.3/gcc/cfgbuild.c b/gcc-4.8.3/gcc/cfgbuild.c new file mode 100644 index 000000000..c47aad0c1 --- /dev/null +++ b/gcc-4.8.3/gcc/cfgbuild.c @@ -0,0 +1,651 @@ +/* Control flow graph building code for GNU compiler. + Copyright (C) 1987-2013 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/>. */ + + +#include "config.h" +#include "system.h" +#include "coretypes.h" +#include "tm.h" +#include "tree.h" +#include "rtl.h" +#include "hard-reg-set.h" +#include "basic-block.h" +#include "regs.h" +#include "flags.h" +#include "function.h" +#include "except.h" +#include "expr.h" +#include "diagnostic-core.h" +#include "timevar.h" +#include "sbitmap.h" + +static void make_edges (basic_block, basic_block, int); +static void make_label_edge (sbitmap, basic_block, rtx, int); +static void find_bb_boundaries (basic_block); +static void compute_outgoing_frequencies (basic_block); + +/* Return true if insn is something that should be contained inside basic + block. */ + +bool +inside_basic_block_p (const_rtx insn) +{ + switch (GET_CODE (insn)) + { + case CODE_LABEL: + /* Avoid creating of basic block for jumptables. */ + return (NEXT_INSN (insn) == 0 + || !JUMP_P (NEXT_INSN (insn)) + || (GET_CODE (PATTERN (NEXT_INSN (insn))) != ADDR_VEC + && GET_CODE (PATTERN (NEXT_INSN (insn))) != ADDR_DIFF_VEC)); + + case JUMP_INSN: + return (GET_CODE (PATTERN (insn)) != ADDR_VEC + && GET_CODE (PATTERN (insn)) != ADDR_DIFF_VEC); + + case CALL_INSN: + case INSN: + case DEBUG_INSN: + return true; + + case BARRIER: + case NOTE: + return false; + + default: + gcc_unreachable (); + } +} + +/* Return true if INSN may cause control flow transfer, so it should be last in + the basic block. */ + +bool +control_flow_insn_p (const_rtx insn) +{ + switch (GET_CODE (insn)) + { + case NOTE: + case CODE_LABEL: + case DEBUG_INSN: + return false; + + case JUMP_INSN: + /* Jump insn always causes control transfer except for tablejumps. */ + return (GET_CODE (PATTERN (insn)) != ADDR_VEC + && GET_CODE (PATTERN (insn)) != ADDR_DIFF_VEC); + + case CALL_INSN: + /* Noreturn and sibling call instructions terminate the basic blocks + (but only if they happen unconditionally). */ + if ((SIBLING_CALL_P (insn) + || find_reg_note (insn, REG_NORETURN, 0)) + && GET_CODE (PATTERN (insn)) != COND_EXEC) + return true; + + /* Call insn may return to the nonlocal goto handler. */ + if (can_nonlocal_goto (insn)) + return true; + break; + + case INSN: + /* Treat trap instructions like noreturn calls (same provision). */ + if (GET_CODE (PATTERN (insn)) == TRAP_IF + && XEXP (PATTERN (insn), 0) == const1_rtx) + return true; + if (!cfun->can_throw_non_call_exceptions) + return false; + break; + + case BARRIER: + /* It is nonsense to reach barrier when looking for the + end of basic block, but before dead code is eliminated + this may happen. */ + return false; + + default: + gcc_unreachable (); + } + + return can_throw_internal (insn); +} + + +/* Create an edge between two basic blocks. FLAGS are auxiliary information + about the edge that is accumulated between calls. */ + +/* Create an edge from a basic block to a label. */ + +static void +make_label_edge (sbitmap edge_cache, basic_block src, rtx label, int flags) +{ + gcc_assert (LABEL_P (label)); + + /* If the label was never emitted, this insn is junk, but avoid a + crash trying to refer to BLOCK_FOR_INSN (label). This can happen + as a result of a syntax error and a diagnostic has already been + printed. */ + + if (INSN_UID (label) == 0) + return; + + cached_make_edge (edge_cache, src, BLOCK_FOR_INSN (label), flags); +} + +/* Create the edges generated by INSN in REGION. */ + +void +rtl_make_eh_edge (sbitmap edge_cache, basic_block src, rtx insn) +{ + eh_landing_pad lp = get_eh_landing_pad_from_rtx (insn); + + if (lp) + { + rtx label = lp->landing_pad; + + /* During initial rtl generation, use the post_landing_pad. */ + if (label == NULL) + { + gcc_assert (lp->post_landing_pad); + label = label_rtx (lp->post_landing_pad); + } + + make_label_edge (edge_cache, src, label, + EDGE_ABNORMAL | EDGE_EH + | (CALL_P (insn) ? EDGE_ABNORMAL_CALL : 0)); + } +} + +/* States of basic block as seen by find_many_sub_basic_blocks. */ +enum state { + /* Basic blocks created via split_block belong to this state. + make_edges will examine these basic blocks to see if we need to + create edges going out of them. */ + BLOCK_NEW = 0, + + /* Basic blocks that do not need examining belong to this state. + These blocks will be left intact. In particular, make_edges will + not create edges going out of these basic blocks. */ + BLOCK_ORIGINAL, + + /* Basic blocks that may need splitting (due to a label appearing in + the middle, etc) belong to this state. After splitting them, + make_edges will create edges going out of them as needed. */ + BLOCK_TO_SPLIT +}; + +#define STATE(BB) (enum state) ((size_t) (BB)->aux) +#define SET_STATE(BB, STATE) ((BB)->aux = (void *) (size_t) (STATE)) + +/* Used internally by purge_dead_tablejump_edges, ORed into state. */ +#define BLOCK_USED_BY_TABLEJUMP 32 +#define FULL_STATE(BB) ((size_t) (BB)->aux) + +/* Identify the edges going out of basic blocks between MIN and MAX, + inclusive, that have their states set to BLOCK_NEW or + BLOCK_TO_SPLIT. + + UPDATE_P should be nonzero if we are updating CFG and zero if we + are building CFG from scratch. */ + +static void +make_edges (basic_block min, basic_block max, int update_p) +{ + basic_block bb; + sbitmap edge_cache = NULL; + + /* Heavy use of computed goto in machine-generated code can lead to + nearly fully-connected CFGs. In that case we spend a significant + amount of time searching the edge lists for duplicates. */ + if (forced_labels || cfun->cfg->max_jumptable_ents > 100) + edge_cache = sbitmap_alloc (last_basic_block); + + /* By nature of the way these get numbered, ENTRY_BLOCK_PTR->next_bb block + is always the entry. */ + if (min == ENTRY_BLOCK_PTR->next_bb) + make_edge (ENTRY_BLOCK_PTR, min, EDGE_FALLTHRU); + + FOR_BB_BETWEEN (bb, min, max->next_bb, next_bb) + { + rtx insn, x; + enum rtx_code code; + edge e; + edge_iterator ei; + + if (STATE (bb) == BLOCK_ORIGINAL) + continue; + + /* If we have an edge cache, cache edges going out of BB. */ + if (edge_cache) + { + bitmap_clear (edge_cache); + if (update_p) + { + FOR_EACH_EDGE (e, ei, bb->succs) + if (e->dest != EXIT_BLOCK_PTR) + bitmap_set_bit (edge_cache, e->dest->index); + } + } + + if (LABEL_P (BB_HEAD (bb)) + && LABEL_ALT_ENTRY_P (BB_HEAD (bb))) + cached_make_edge (NULL, ENTRY_BLOCK_PTR, bb, 0); + + /* Examine the last instruction of the block, and discover the + ways we can leave the block. */ + + insn = BB_END (bb); + code = GET_CODE (insn); + + /* A branch. */ + if (code == JUMP_INSN) + { + rtx tmp; + + /* Recognize a non-local goto as a branch outside the + current function. */ + if (find_reg_note (insn, REG_NON_LOCAL_GOTO, NULL_RTX)) + ; + + /* Recognize a tablejump and do the right thing. */ + else if (tablejump_p (insn, NULL, &tmp)) + { + rtvec vec; + int j; + + if (GET_CODE (PATTERN (tmp)) == ADDR_VEC) + vec = XVEC (PATTERN (tmp), 0); + else + vec = XVEC (PATTERN (tmp), 1); + + for (j = GET_NUM_ELEM (vec) - 1; j >= 0; --j) + make_label_edge (edge_cache, bb, + XEXP (RTVEC_ELT (vec, j), 0), 0); + + /* Some targets (eg, ARM) emit a conditional jump that also + contains the out-of-range target. Scan for these and + add an edge if necessary. */ + if ((tmp = single_set (insn)) != NULL + && SET_DEST (tmp) == pc_rtx + && GET_CODE (SET_SRC (tmp)) == IF_THEN_ELSE + && GET_CODE (XEXP (SET_SRC (tmp), 2)) == LABEL_REF) + make_label_edge (edge_cache, bb, + XEXP (XEXP (SET_SRC (tmp), 2), 0), 0); + } + + /* If this is a computed jump, then mark it as reaching + everything on the forced_labels list. */ + else if (computed_jump_p (insn)) + { + for (x = forced_labels; x; x = XEXP (x, 1)) + make_label_edge (edge_cache, bb, XEXP (x, 0), EDGE_ABNORMAL); + } + + /* Returns create an exit out. */ + else if (returnjump_p (insn)) + cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR, 0); + + /* Recognize asm goto and do the right thing. */ + else if ((tmp = extract_asm_operands (PATTERN (insn))) != NULL) + { + int i, n = ASM_OPERANDS_LABEL_LENGTH (tmp); + for (i = 0; i < n; ++i) + make_label_edge (edge_cache, bb, + XEXP (ASM_OPERANDS_LABEL (tmp, i), 0), 0); + } + + /* Otherwise, we have a plain conditional or unconditional jump. */ + else + { + gcc_assert (JUMP_LABEL (insn)); + make_label_edge (edge_cache, bb, JUMP_LABEL (insn), 0); + } + } + + /* If this is a sibling call insn, then this is in effect a combined call + and return, and so we need an edge to the exit block. No need to + worry about EH edges, since we wouldn't have created the sibling call + in the first place. */ + if (code == CALL_INSN && SIBLING_CALL_P (insn)) + cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR, + EDGE_SIBCALL | EDGE_ABNORMAL); + + /* If this is a CALL_INSN, then mark it as reaching the active EH + handler for this CALL_INSN. If we're handling non-call + exceptions then any insn can reach any of the active handlers. + Also mark the CALL_INSN as reaching any nonlocal goto handler. */ + else if (code == CALL_INSN || cfun->can_throw_non_call_exceptions) + { + /* Add any appropriate EH edges. */ + rtl_make_eh_edge (edge_cache, bb, insn); + + if (code == CALL_INSN) + { + if (can_nonlocal_goto (insn)) + { + /* ??? This could be made smarter: in some cases it's + possible to tell that certain calls will not do a + nonlocal goto. For example, if the nested functions + that do the nonlocal gotos do not have their addresses + taken, then only calls to those functions or to other + nested functions that use them could possibly do + nonlocal gotos. */ + for (x = nonlocal_goto_handler_labels; x; x = XEXP (x, 1)) + make_label_edge (edge_cache, bb, XEXP (x, 0), + EDGE_ABNORMAL | EDGE_ABNORMAL_CALL); + } + + if (flag_tm) + { + rtx note; + for (note = REG_NOTES (insn); note; note = XEXP (note, 1)) + if (REG_NOTE_KIND (note) == REG_TM) + make_label_edge (edge_cache, bb, XEXP (note, 0), + EDGE_ABNORMAL | EDGE_ABNORMAL_CALL); + } + } + } + + /* Find out if we can drop through to the next block. */ + insn = NEXT_INSN (insn); + e = find_edge (bb, EXIT_BLOCK_PTR); + if (e && e->flags & EDGE_FALLTHRU) + insn = NULL; + + while (insn + && NOTE_P (insn) + && NOTE_KIND (insn) != NOTE_INSN_BASIC_BLOCK) + insn = NEXT_INSN (insn); + + if (!insn) + cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR, EDGE_FALLTHRU); + else if (bb->next_bb != EXIT_BLOCK_PTR) + { + if (insn == BB_HEAD (bb->next_bb)) + cached_make_edge (edge_cache, bb, bb->next_bb, EDGE_FALLTHRU); + } + } + + if (edge_cache) + sbitmap_free (edge_cache); +} + +static void +mark_tablejump_edge (rtx label) +{ + basic_block bb; + + gcc_assert (LABEL_P (label)); + /* See comment in make_label_edge. */ + if (INSN_UID (label) == 0) + return; + bb = BLOCK_FOR_INSN (label); + SET_STATE (bb, FULL_STATE (bb) | BLOCK_USED_BY_TABLEJUMP); +} + +static void +purge_dead_tablejump_edges (basic_block bb, rtx table) +{ + rtx insn = BB_END (bb), tmp; + rtvec vec; + int j; + edge_iterator ei; + edge e; + + if (GET_CODE (PATTERN (table)) == ADDR_VEC) + vec = XVEC (PATTERN (table), 0); + else + vec = XVEC (PATTERN (table), 1); + + for (j = GET_NUM_ELEM (vec) - 1; j >= 0; --j) + mark_tablejump_edge (XEXP (RTVEC_ELT (vec, j), 0)); + + /* Some targets (eg, ARM) emit a conditional jump that also + contains the out-of-range target. Scan for these and + add an edge if necessary. */ + if ((tmp = single_set (insn)) != NULL + && SET_DEST (tmp) == pc_rtx + && GET_CODE (SET_SRC (tmp)) == IF_THEN_ELSE + && GET_CODE (XEXP (SET_SRC (tmp), 2)) == LABEL_REF) + mark_tablejump_edge (XEXP (XEXP (SET_SRC (tmp), 2), 0)); + + for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); ) + { + if (FULL_STATE (e->dest) & BLOCK_USED_BY_TABLEJUMP) + SET_STATE (e->dest, FULL_STATE (e->dest) + & ~(size_t) BLOCK_USED_BY_TABLEJUMP); + else if (!(e->flags & (EDGE_ABNORMAL | EDGE_EH))) + { + remove_edge (e); + continue; + } + ei_next (&ei); + } +} + +/* Scan basic block BB for possible BB boundaries inside the block + and create new basic blocks in the progress. */ + +static void +find_bb_boundaries (basic_block bb) +{ + basic_block orig_bb = bb; + rtx insn = BB_HEAD (bb); + rtx end = BB_END (bb), x; + rtx table; + rtx flow_transfer_insn = NULL_RTX; + edge fallthru = NULL; + + if (insn == BB_END (bb)) + return; + + if (LABEL_P (insn)) + insn = NEXT_INSN (insn); + + /* Scan insn chain and try to find new basic block boundaries. */ + while (1) + { + enum rtx_code code = GET_CODE (insn); + + /* In case we've previously seen an insn that effects a control + flow transfer, split the block. */ + if ((flow_transfer_insn || code == CODE_LABEL) + && inside_basic_block_p (insn)) + { + fallthru = split_block (bb, PREV_INSN (insn)); + if (flow_transfer_insn) + { + BB_END (bb) = flow_transfer_insn; + + /* Clean up the bb field for the insns between the blocks. */ + for (x = NEXT_INSN (flow_transfer_insn); + x != BB_HEAD (fallthru->dest); + x = NEXT_INSN (x)) + if (!BARRIER_P (x)) + set_block_for_insn (x, NULL); + } + + bb = fallthru->dest; + remove_edge (fallthru); + flow_transfer_insn = NULL_RTX; + if (code == CODE_LABEL && LABEL_ALT_ENTRY_P (insn)) + make_edge (ENTRY_BLOCK_PTR, bb, 0); + } + else if (code == BARRIER) + { + /* __builtin_unreachable () may cause a barrier to be emitted in + the middle of a BB. We need to split it in the same manner as + if the barrier were preceded by a control_flow_insn_p insn. */ + if (!flow_transfer_insn) + flow_transfer_insn = prev_nonnote_insn_bb (insn); + } + + if (control_flow_insn_p (insn)) + flow_transfer_insn = insn; + if (insn == end) + break; + insn = NEXT_INSN (insn); + } + + /* In case expander replaced normal insn by sequence terminating by + return and barrier, or possibly other sequence not behaving like + ordinary jump, we need to take care and move basic block boundary. */ + if (flow_transfer_insn) + { + BB_END (bb) = flow_transfer_insn; + + /* Clean up the bb field for the insns that do not belong to BB. */ + x = flow_transfer_insn; + while (x != end) + { + x = NEXT_INSN (x); + if (!BARRIER_P (x)) + set_block_for_insn (x, NULL); + } + } + + /* We've possibly replaced the conditional jump by conditional jump + followed by cleanup at fallthru edge, so the outgoing edges may + be dead. */ + purge_dead_edges (bb); + + /* purge_dead_edges doesn't handle tablejump's, but if we have split the + basic block, we might need to kill some edges. */ + if (bb != orig_bb && tablejump_p (BB_END (bb), NULL, &table)) + purge_dead_tablejump_edges (bb, table); +} + +/* Assume that frequency of basic block B is known. Compute frequencies + and probabilities of outgoing edges. */ + +static void +compute_outgoing_frequencies (basic_block b) +{ + edge e, f; + edge_iterator ei; + + if (EDGE_COUNT (b->succs) == 2) + { + rtx note = find_reg_note (BB_END (b), REG_BR_PROB, NULL); + int probability; + + if (note) + { + probability = INTVAL (XEXP (note, 0)); + e = BRANCH_EDGE (b); + e->probability = probability; + e->count = ((b->count * probability + REG_BR_PROB_BASE / 2) + / REG_BR_PROB_BASE); + f = FALLTHRU_EDGE (b); + f->probability = REG_BR_PROB_BASE - probability; + f->count = b->count - e->count; + return; + } + else + { + guess_outgoing_edge_probabilities (b); + } + } + else if (single_succ_p (b)) + { + e = single_succ_edge (b); + e->probability = REG_BR_PROB_BASE; + e->count = b->count; + return; + } + else + { + /* We rely on BBs with more than two successors to have sane probabilities + and do not guess them here. For BBs terminated by switch statements + expanded to jump-table jump, we have done the right thing during + expansion. For EH edges, we still guess the probabilities here. */ + bool complex_edge = false; + FOR_EACH_EDGE (e, ei, b->succs) + if (e->flags & EDGE_COMPLEX) + { + complex_edge = true; + break; + } + if (complex_edge) + guess_outgoing_edge_probabilities (b); + } + + if (b->count) + FOR_EACH_EDGE (e, ei, b->succs) + e->count = ((b->count * e->probability + REG_BR_PROB_BASE / 2) + / REG_BR_PROB_BASE); +} + +/* Assume that some pass has inserted labels or control flow + instructions within a basic block. Split basic blocks as needed + and create edges. */ + +void +find_many_sub_basic_blocks (sbitmap blocks) +{ + basic_block bb, min, max; + + FOR_EACH_BB (bb) + SET_STATE (bb, + bitmap_bit_p (blocks, bb->index) ? BLOCK_TO_SPLIT : BLOCK_ORIGINAL); + + FOR_EACH_BB (bb) + if (STATE (bb) == BLOCK_TO_SPLIT) + find_bb_boundaries (bb); + + FOR_EACH_BB (bb) + if (STATE (bb) != BLOCK_ORIGINAL) + break; + + min = max = bb; + for (; bb != EXIT_BLOCK_PTR; bb = bb->next_bb) + if (STATE (bb) != BLOCK_ORIGINAL) + max = bb; + + /* Now re-scan and wire in all edges. This expect simple (conditional) + jumps at the end of each new basic blocks. */ + make_edges (min, max, 1); + + /* Update branch probabilities. Expect only (un)conditional jumps + to be created with only the forward edges. */ + if (profile_status != PROFILE_ABSENT) + FOR_BB_BETWEEN (bb, min, max->next_bb, next_bb) + { + edge e; + edge_iterator ei; + + if (STATE (bb) == BLOCK_ORIGINAL) + continue; + if (STATE (bb) == BLOCK_NEW) + { + bb->count = 0; + bb->frequency = 0; + FOR_EACH_EDGE (e, ei, bb->preds) + { + bb->count += e->count; + bb->frequency += EDGE_FREQUENCY (e); + } + } + + compute_outgoing_frequencies (bb); + } + + FOR_EACH_BB (bb) + SET_STATE (bb, 0); +} |