| /* Global constant/copy propagation for RTL. |
| Copyright (C) 1997-2015 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 "diagnostic-core.h" |
| #include "toplev.h" |
| #include "rtl.h" |
| #include "hash-set.h" |
| #include "machmode.h" |
| #include "vec.h" |
| #include "double-int.h" |
| #include "input.h" |
| #include "alias.h" |
| #include "symtab.h" |
| #include "wide-int.h" |
| #include "inchash.h" |
| #include "tree.h" |
| #include "tm_p.h" |
| #include "regs.h" |
| #include "hard-reg-set.h" |
| #include "flags.h" |
| #include "insn-config.h" |
| #include "recog.h" |
| #include "predict.h" |
| #include "hashtab.h" |
| #include "function.h" |
| #include "dominance.h" |
| #include "cfg.h" |
| #include "cfgrtl.h" |
| #include "cfganal.h" |
| #include "lcm.h" |
| #include "cfgcleanup.h" |
| #include "basic-block.h" |
| #include "statistics.h" |
| #include "real.h" |
| #include "fixed-value.h" |
| #include "expmed.h" |
| #include "dojump.h" |
| #include "explow.h" |
| #include "calls.h" |
| #include "emit-rtl.h" |
| #include "varasm.h" |
| #include "stmt.h" |
| #include "expr.h" |
| #include "except.h" |
| #include "params.h" |
| #include "cselib.h" |
| #include "intl.h" |
| #include "obstack.h" |
| #include "tree-pass.h" |
| #include "df.h" |
| #include "dbgcnt.h" |
| #include "target.h" |
| #include "cfgloop.h" |
| |
| |
| /* An obstack for our working variables. */ |
| static struct obstack cprop_obstack; |
| |
| /* Occurrence of an expression. |
| There is one per basic block. If a pattern appears more than once the |
| last appearance is used. */ |
| |
| struct cprop_occr |
| { |
| /* Next occurrence of this expression. */ |
| struct cprop_occr *next; |
| /* The insn that computes the expression. */ |
| rtx_insn *insn; |
| }; |
| |
| typedef struct cprop_occr *occr_t; |
| |
| /* Hash table entry for assignment expressions. */ |
| |
| struct cprop_expr |
| { |
| /* The expression (DEST := SRC). */ |
| rtx dest; |
| rtx src; |
| |
| /* Index in the available expression bitmaps. */ |
| int bitmap_index; |
| /* Next entry with the same hash. */ |
| struct cprop_expr *next_same_hash; |
| /* List of available occurrence in basic blocks in the function. |
| An "available occurrence" is one that is the last occurrence in the |
| basic block and whose operands are not modified by following statements |
| in the basic block [including this insn]. */ |
| struct cprop_occr *avail_occr; |
| }; |
| |
| /* Hash table for copy propagation expressions. |
| Each hash table is an array of buckets. |
| ??? It is known that if it were an array of entries, structure elements |
| `next_same_hash' and `bitmap_index' wouldn't be necessary. However, it is |
| not clear whether in the final analysis a sufficient amount of memory would |
| be saved as the size of the available expression bitmaps would be larger |
| [one could build a mapping table without holes afterwards though]. |
| Someday I'll perform the computation and figure it out. */ |
| |
| struct hash_table_d |
| { |
| /* The table itself. |
| This is an array of `set_hash_table_size' elements. */ |
| struct cprop_expr **table; |
| |
| /* Size of the hash table, in elements. */ |
| unsigned int size; |
| |
| /* Number of hash table elements. */ |
| unsigned int n_elems; |
| }; |
| |
| /* Copy propagation hash table. */ |
| static struct hash_table_d set_hash_table; |
| |
| /* Array of implicit set patterns indexed by basic block index. */ |
| static rtx *implicit_sets; |
| |
| /* Array of indexes of expressions for implicit set patterns indexed by basic |
| block index. In other words, implicit_set_indexes[i] is the bitmap_index |
| of the expression whose RTX is implicit_sets[i]. */ |
| static int *implicit_set_indexes; |
| |
| /* Bitmap containing one bit for each register in the program. |
| Used when performing GCSE to track which registers have been set since |
| the start or end of the basic block while traversing that block. */ |
| static regset reg_set_bitmap; |
| |
| /* Various variables for statistics gathering. */ |
| |
| /* Memory used in a pass. |
| This isn't intended to be absolutely precise. Its intent is only |
| to keep an eye on memory usage. */ |
| static int bytes_used; |
| |
| /* Number of local constants propagated. */ |
| static int local_const_prop_count; |
| /* Number of local copies propagated. */ |
| static int local_copy_prop_count; |
| /* Number of global constants propagated. */ |
| static int global_const_prop_count; |
| /* Number of global copies propagated. */ |
| static int global_copy_prop_count; |
| |
| #define GOBNEW(T) ((T *) cprop_alloc (sizeof (T))) |
| #define GOBNEWVAR(T, S) ((T *) cprop_alloc ((S))) |
| |
| /* Cover function to obstack_alloc. */ |
| |
| static void * |
| cprop_alloc (unsigned long size) |
| { |
| bytes_used += size; |
| return obstack_alloc (&cprop_obstack, size); |
| } |
| |
| /* Return nonzero if register X is unchanged from INSN to the end |
| of INSN's basic block. */ |
| |
| static int |
| reg_available_p (const_rtx x, const rtx_insn *insn ATTRIBUTE_UNUSED) |
| { |
| return ! REGNO_REG_SET_P (reg_set_bitmap, REGNO (x)); |
| } |
| |
| /* Hash a set of register REGNO. |
| |
| Sets are hashed on the register that is set. This simplifies the PRE copy |
| propagation code. |
| |
| ??? May need to make things more elaborate. Later, as necessary. */ |
| |
| static unsigned int |
| hash_mod (int regno, int hash_table_size) |
| { |
| return (unsigned) regno % hash_table_size; |
| } |
| |
| /* Insert assignment DEST:=SET from INSN in the hash table. |
| DEST is a register and SET is a register or a suitable constant. |
| If the assignment is already present in the table, record it as |
| the last occurrence in INSN's basic block. |
| IMPLICIT is true if it's an implicit set, false otherwise. */ |
| |
| static void |
| insert_set_in_table (rtx dest, rtx src, rtx_insn *insn, |
| struct hash_table_d *table, bool implicit) |
| { |
| bool found = false; |
| unsigned int hash; |
| struct cprop_expr *cur_expr, *last_expr = NULL; |
| struct cprop_occr *cur_occr; |
| |
| hash = hash_mod (REGNO (dest), table->size); |
| |
| for (cur_expr = table->table[hash]; cur_expr; |
| cur_expr = cur_expr->next_same_hash) |
| { |
| if (dest == cur_expr->dest |
| && src == cur_expr->src) |
| { |
| found = true; |
| break; |
| } |
| last_expr = cur_expr; |
| } |
| |
| if (! found) |
| { |
| cur_expr = GOBNEW (struct cprop_expr); |
| bytes_used += sizeof (struct cprop_expr); |
| if (table->table[hash] == NULL) |
| /* This is the first pattern that hashed to this index. */ |
| table->table[hash] = cur_expr; |
| else |
| /* Add EXPR to end of this hash chain. */ |
| last_expr->next_same_hash = cur_expr; |
| |
| /* Set the fields of the expr element. |
| We must copy X because it can be modified when copy propagation is |
| performed on its operands. */ |
| cur_expr->dest = copy_rtx (dest); |
| cur_expr->src = copy_rtx (src); |
| cur_expr->bitmap_index = table->n_elems++; |
| cur_expr->next_same_hash = NULL; |
| cur_expr->avail_occr = NULL; |
| } |
| |
| /* Now record the occurrence. */ |
| cur_occr = cur_expr->avail_occr; |
| |
| if (cur_occr |
| && BLOCK_FOR_INSN (cur_occr->insn) == BLOCK_FOR_INSN (insn)) |
| { |
| /* Found another instance of the expression in the same basic block. |
| Prefer this occurrence to the currently recorded one. We want |
| the last one in the block and the block is scanned from start |
| to end. */ |
| cur_occr->insn = insn; |
| } |
| else |
| { |
| /* First occurrence of this expression in this basic block. */ |
| cur_occr = GOBNEW (struct cprop_occr); |
| bytes_used += sizeof (struct cprop_occr); |
| cur_occr->insn = insn; |
| cur_occr->next = cur_expr->avail_occr; |
| cur_expr->avail_occr = cur_occr; |
| } |
| |
| /* Record bitmap_index of the implicit set in implicit_set_indexes. */ |
| if (implicit) |
| implicit_set_indexes[BLOCK_FOR_INSN (insn)->index] |
| = cur_expr->bitmap_index; |
| } |
| |
| /* Determine whether the rtx X should be treated as a constant for CPROP. |
| Since X might be inserted more than once we have to take care that it |
| is sharable. */ |
| |
| static bool |
| cprop_constant_p (const_rtx x) |
| { |
| return CONSTANT_P (x) && (GET_CODE (x) != CONST || shared_const_p (x)); |
| } |
| |
| /* Scan SET present in INSN and add an entry to the hash TABLE. |
| IMPLICIT is true if it's an implicit set, false otherwise. */ |
| |
| static void |
| hash_scan_set (rtx set, rtx_insn *insn, struct hash_table_d *table, |
| bool implicit) |
| { |
| rtx src = SET_SRC (set); |
| rtx dest = SET_DEST (set); |
| |
| if (REG_P (dest) |
| && ! HARD_REGISTER_P (dest) |
| && reg_available_p (dest, insn) |
| && can_copy_p (GET_MODE (dest))) |
| { |
| /* See if a REG_EQUAL note shows this equivalent to a simpler expression. |
| |
| This allows us to do a single CPROP pass and still eliminate |
| redundant constants, addresses or other expressions that are |
| constructed with multiple instructions. |
| |
| However, keep the original SRC if INSN is a simple reg-reg move. In |
| In this case, there will almost always be a REG_EQUAL note on the |
| insn that sets SRC. By recording the REG_EQUAL value here as SRC |
| for INSN, we miss copy propagation opportunities. |
| |
| Note that this does not impede profitable constant propagations. We |
| "look through" reg-reg sets in lookup_set. */ |
| rtx note = find_reg_equal_equiv_note (insn); |
| if (note != 0 |
| && REG_NOTE_KIND (note) == REG_EQUAL |
| && !REG_P (src) |
| && cprop_constant_p (XEXP (note, 0))) |
| src = XEXP (note, 0), set = gen_rtx_SET (VOIDmode, dest, src); |
| |
| /* Record sets for constant/copy propagation. */ |
| if ((REG_P (src) |
| && src != dest |
| && ! HARD_REGISTER_P (src) |
| && reg_available_p (src, insn)) |
| || cprop_constant_p (src)) |
| insert_set_in_table (dest, src, insn, table, implicit); |
| } |
| } |
| |
| /* Process INSN and add hash table entries as appropriate. */ |
| |
| static void |
| hash_scan_insn (rtx_insn *insn, struct hash_table_d *table) |
| { |
| rtx pat = PATTERN (insn); |
| int i; |
| |
| /* Pick out the sets of INSN and for other forms of instructions record |
| what's been modified. */ |
| |
| if (GET_CODE (pat) == SET) |
| hash_scan_set (pat, insn, table, false); |
| else if (GET_CODE (pat) == PARALLEL) |
| for (i = 0; i < XVECLEN (pat, 0); i++) |
| { |
| rtx x = XVECEXP (pat, 0, i); |
| |
| if (GET_CODE (x) == SET) |
| hash_scan_set (x, insn, table, false); |
| } |
| } |
| |
| /* Dump the hash table TABLE to file FILE under the name NAME. */ |
| |
| static void |
| dump_hash_table (FILE *file, const char *name, struct hash_table_d *table) |
| { |
| int i; |
| /* Flattened out table, so it's printed in proper order. */ |
| struct cprop_expr **flat_table; |
| unsigned int *hash_val; |
| struct cprop_expr *expr; |
| |
| flat_table = XCNEWVEC (struct cprop_expr *, table->n_elems); |
| hash_val = XNEWVEC (unsigned int, table->n_elems); |
| |
| for (i = 0; i < (int) table->size; i++) |
| for (expr = table->table[i]; expr != NULL; expr = expr->next_same_hash) |
| { |
| flat_table[expr->bitmap_index] = expr; |
| hash_val[expr->bitmap_index] = i; |
| } |
| |
| fprintf (file, "%s hash table (%d buckets, %d entries)\n", |
| name, table->size, table->n_elems); |
| |
| for (i = 0; i < (int) table->n_elems; i++) |
| if (flat_table[i] != 0) |
| { |
| expr = flat_table[i]; |
| fprintf (file, "Index %d (hash value %d)\n ", |
| expr->bitmap_index, hash_val[i]); |
| print_rtl (file, expr->dest); |
| fprintf (file, " := "); |
| print_rtl (file, expr->src); |
| fprintf (file, "\n"); |
| } |
| |
| fprintf (file, "\n"); |
| |
| free (flat_table); |
| free (hash_val); |
| } |
| |
| /* Record as unavailable all registers that are DEF operands of INSN. */ |
| |
| static void |
| make_set_regs_unavailable (rtx_insn *insn) |
| { |
| df_ref def; |
| |
| FOR_EACH_INSN_DEF (def, insn) |
| SET_REGNO_REG_SET (reg_set_bitmap, DF_REF_REGNO (def)); |
| } |
| |
| /* Top level function to create an assignment hash table. |
| |
| Assignment entries are placed in the hash table if |
| - they are of the form (set (pseudo-reg) src), |
| - src is something we want to perform const/copy propagation on, |
| - none of the operands or target are subsequently modified in the block |
| |
| Currently src must be a pseudo-reg or a const_int. |
| |
| TABLE is the table computed. */ |
| |
| static void |
| compute_hash_table_work (struct hash_table_d *table) |
| { |
| basic_block bb; |
| |
| /* Allocate vars to track sets of regs. */ |
| reg_set_bitmap = ALLOC_REG_SET (NULL); |
| |
| FOR_EACH_BB_FN (bb, cfun) |
| { |
| rtx_insn *insn; |
| |
| /* Reset tables used to keep track of what's not yet invalid [since |
| the end of the block]. */ |
| CLEAR_REG_SET (reg_set_bitmap); |
| |
| /* Go over all insns from the last to the first. This is convenient |
| for tracking available registers, i.e. not set between INSN and |
| the end of the basic block BB. */ |
| FOR_BB_INSNS_REVERSE (bb, insn) |
| { |
| /* Only real insns are interesting. */ |
| if (!NONDEBUG_INSN_P (insn)) |
| continue; |
| |
| /* Record interesting sets from INSN in the hash table. */ |
| hash_scan_insn (insn, table); |
| |
| /* Any registers set in INSN will make SETs above it not AVAIL. */ |
| make_set_regs_unavailable (insn); |
| } |
| |
| /* Insert implicit sets in the hash table, pretending they appear as |
| insns at the head of the basic block. */ |
| if (implicit_sets[bb->index] != NULL_RTX) |
| hash_scan_set (implicit_sets[bb->index], BB_HEAD (bb), table, true); |
| } |
| |
| FREE_REG_SET (reg_set_bitmap); |
| } |
| |
| /* Allocate space for the set/expr hash TABLE. |
| It is used to determine the number of buckets to use. */ |
| |
| static void |
| alloc_hash_table (struct hash_table_d *table) |
| { |
| int n; |
| |
| n = get_max_insn_count (); |
| |
| table->size = n / 4; |
| if (table->size < 11) |
| table->size = 11; |
| |
| /* Attempt to maintain efficient use of hash table. |
| Making it an odd number is simplest for now. |
| ??? Later take some measurements. */ |
| table->size |= 1; |
| n = table->size * sizeof (struct cprop_expr *); |
| table->table = XNEWVAR (struct cprop_expr *, n); |
| } |
| |
| /* Free things allocated by alloc_hash_table. */ |
| |
| static void |
| free_hash_table (struct hash_table_d *table) |
| { |
| free (table->table); |
| } |
| |
| /* Compute the hash TABLE for doing copy/const propagation or |
| expression hash table. */ |
| |
| static void |
| compute_hash_table (struct hash_table_d *table) |
| { |
| /* Initialize count of number of entries in hash table. */ |
| table->n_elems = 0; |
| memset (table->table, 0, table->size * sizeof (struct cprop_expr *)); |
| |
| compute_hash_table_work (table); |
| } |
| |
| /* Expression tracking support. */ |
| |
| /* Lookup REGNO in the set TABLE. The result is a pointer to the |
| table entry, or NULL if not found. */ |
| |
| static struct cprop_expr * |
| lookup_set (unsigned int regno, struct hash_table_d *table) |
| { |
| unsigned int hash = hash_mod (regno, table->size); |
| struct cprop_expr *expr; |
| |
| expr = table->table[hash]; |
| |
| while (expr && REGNO (expr->dest) != regno) |
| expr = expr->next_same_hash; |
| |
| return expr; |
| } |
| |
| /* Return the next entry for REGNO in list EXPR. */ |
| |
| static struct cprop_expr * |
| next_set (unsigned int regno, struct cprop_expr *expr) |
| { |
| do |
| expr = expr->next_same_hash; |
| while (expr && REGNO (expr->dest) != regno); |
| |
| return expr; |
| } |
| |
| /* Reset tables used to keep track of what's still available [since the |
| start of the block]. */ |
| |
| static void |
| reset_opr_set_tables (void) |
| { |
| /* Maintain a bitmap of which regs have been set since beginning of |
| the block. */ |
| CLEAR_REG_SET (reg_set_bitmap); |
| } |
| |
| /* Return nonzero if the register X has not been set yet [since the |
| start of the basic block containing INSN]. */ |
| |
| static int |
| reg_not_set_p (const_rtx x, const rtx_insn *insn ATTRIBUTE_UNUSED) |
| { |
| return ! REGNO_REG_SET_P (reg_set_bitmap, REGNO (x)); |
| } |
| |
| /* Record things set by INSN. |
| This data is used by reg_not_set_p. */ |
| |
| static void |
| mark_oprs_set (rtx_insn *insn) |
| { |
| df_ref def; |
| |
| FOR_EACH_INSN_DEF (def, insn) |
| SET_REGNO_REG_SET (reg_set_bitmap, DF_REF_REGNO (def)); |
| } |
| |
| /* Compute copy/constant propagation working variables. */ |
| |
| /* Local properties of assignments. */ |
| static sbitmap *cprop_avloc; |
| static sbitmap *cprop_kill; |
| |
| /* Global properties of assignments (computed from the local properties). */ |
| static sbitmap *cprop_avin; |
| static sbitmap *cprop_avout; |
| |
| /* Allocate vars used for copy/const propagation. N_BLOCKS is the number of |
| basic blocks. N_SETS is the number of sets. */ |
| |
| static void |
| alloc_cprop_mem (int n_blocks, int n_sets) |
| { |
| cprop_avloc = sbitmap_vector_alloc (n_blocks, n_sets); |
| cprop_kill = sbitmap_vector_alloc (n_blocks, n_sets); |
| |
| cprop_avin = sbitmap_vector_alloc (n_blocks, n_sets); |
| cprop_avout = sbitmap_vector_alloc (n_blocks, n_sets); |
| } |
| |
| /* Free vars used by copy/const propagation. */ |
| |
| static void |
| free_cprop_mem (void) |
| { |
| sbitmap_vector_free (cprop_avloc); |
| sbitmap_vector_free (cprop_kill); |
| sbitmap_vector_free (cprop_avin); |
| sbitmap_vector_free (cprop_avout); |
| } |
| |
| /* Compute the local properties of each recorded expression. |
| |
| Local properties are those that are defined by the block, irrespective of |
| other blocks. |
| |
| An expression is killed in a block if its operands, either DEST or SRC, are |
| modified in the block. |
| |
| An expression is computed (locally available) in a block if it is computed |
| at least once and expression would contain the same value if the |
| computation was moved to the end of the block. |
| |
| KILL and COMP are destination sbitmaps for recording local properties. */ |
| |
| static void |
| compute_local_properties (sbitmap *kill, sbitmap *comp, |
| struct hash_table_d *table) |
| { |
| unsigned int i; |
| |
| /* Initialize the bitmaps that were passed in. */ |
| bitmap_vector_clear (kill, last_basic_block_for_fn (cfun)); |
| bitmap_vector_clear (comp, last_basic_block_for_fn (cfun)); |
| |
| for (i = 0; i < table->size; i++) |
| { |
| struct cprop_expr *expr; |
| |
| for (expr = table->table[i]; expr != NULL; expr = expr->next_same_hash) |
| { |
| int indx = expr->bitmap_index; |
| df_ref def; |
| struct cprop_occr *occr; |
| |
| /* For each definition of the destination pseudo-reg, the expression |
| is killed in the block where the definition is. */ |
| for (def = DF_REG_DEF_CHAIN (REGNO (expr->dest)); |
| def; def = DF_REF_NEXT_REG (def)) |
| bitmap_set_bit (kill[DF_REF_BB (def)->index], indx); |
| |
| /* If the source is a pseudo-reg, for each definition of the source, |
| the expression is killed in the block where the definition is. */ |
| if (REG_P (expr->src)) |
| for (def = DF_REG_DEF_CHAIN (REGNO (expr->src)); |
| def; def = DF_REF_NEXT_REG (def)) |
| bitmap_set_bit (kill[DF_REF_BB (def)->index], indx); |
| |
| /* The occurrences recorded in avail_occr are exactly those that |
| are locally available in the block where they are. */ |
| for (occr = expr->avail_occr; occr != NULL; occr = occr->next) |
| { |
| bitmap_set_bit (comp[BLOCK_FOR_INSN (occr->insn)->index], indx); |
| } |
| } |
| } |
| } |
| |
| /* Hash table support. */ |
| |
| /* Top level routine to do the dataflow analysis needed by copy/const |
| propagation. */ |
| |
| static void |
| compute_cprop_data (void) |
| { |
| basic_block bb; |
| |
| compute_local_properties (cprop_kill, cprop_avloc, &set_hash_table); |
| compute_available (cprop_avloc, cprop_kill, cprop_avout, cprop_avin); |
| |
| /* Merge implicit sets into CPROP_AVIN. They are always available at the |
| entry of their basic block. We need to do this because 1) implicit sets |
| aren't recorded for the local pass so they cannot be propagated within |
| their basic block by this pass and 2) the global pass would otherwise |
| propagate them only in the successors of their basic block. */ |
| FOR_EACH_BB_FN (bb, cfun) |
| { |
| int index = implicit_set_indexes[bb->index]; |
| if (index != -1) |
| bitmap_set_bit (cprop_avin[bb->index], index); |
| } |
| } |
| |
| /* Copy/constant propagation. */ |
| |
| /* Maximum number of register uses in an insn that we handle. */ |
| #define MAX_USES 8 |
| |
| /* Table of uses (registers, both hard and pseudo) found in an insn. |
| Allocated statically to avoid alloc/free complexity and overhead. */ |
| static rtx reg_use_table[MAX_USES]; |
| |
| /* Index into `reg_use_table' while building it. */ |
| static unsigned reg_use_count; |
| |
| /* Set up a list of register numbers used in INSN. The found uses are stored |
| in `reg_use_table'. `reg_use_count' is initialized to zero before entry, |
| and contains the number of uses in the table upon exit. |
| |
| ??? If a register appears multiple times we will record it multiple times. |
| This doesn't hurt anything but it will slow things down. */ |
| |
| static void |
| find_used_regs (rtx *xptr, void *data ATTRIBUTE_UNUSED) |
| { |
| int i, j; |
| enum rtx_code code; |
| const char *fmt; |
| rtx x = *xptr; |
| |
| /* repeat is used to turn tail-recursion into iteration since GCC |
| can't do it when there's no return value. */ |
| repeat: |
| if (x == 0) |
| return; |
| |
| code = GET_CODE (x); |
| if (REG_P (x)) |
| { |
| if (reg_use_count == MAX_USES) |
| return; |
| |
| reg_use_table[reg_use_count] = x; |
| reg_use_count++; |
| } |
| |
| /* Recursively scan the operands of this expression. */ |
| |
| for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--) |
| { |
| if (fmt[i] == 'e') |
| { |
| /* If we are about to do the last recursive call |
| needed at this level, change it into iteration. |
| This function is called enough to be worth it. */ |
| if (i == 0) |
| { |
| x = XEXP (x, 0); |
| goto repeat; |
| } |
| |
| find_used_regs (&XEXP (x, i), data); |
| } |
| else if (fmt[i] == 'E') |
| for (j = 0; j < XVECLEN (x, i); j++) |
| find_used_regs (&XVECEXP (x, i, j), data); |
| } |
| } |
| |
| /* Try to replace all uses of FROM in INSN with TO. |
| Return nonzero if successful. */ |
| |
| static int |
| try_replace_reg (rtx from, rtx to, rtx_insn *insn) |
| { |
| rtx note = find_reg_equal_equiv_note (insn); |
| rtx src = 0; |
| int success = 0; |
| rtx set = single_set (insn); |
| |
| /* Usually we substitute easy stuff, so we won't copy everything. |
| We however need to take care to not duplicate non-trivial CONST |
| expressions. */ |
| to = copy_rtx (to); |
| |
| validate_replace_src_group (from, to, insn); |
| if (num_changes_pending () && apply_change_group ()) |
| success = 1; |
| |
| /* Try to simplify SET_SRC if we have substituted a constant. */ |
| if (success && set && CONSTANT_P (to)) |
| { |
| src = simplify_rtx (SET_SRC (set)); |
| |
| if (src) |
| validate_change (insn, &SET_SRC (set), src, 0); |
| } |
| |
| /* If there is already a REG_EQUAL note, update the expression in it |
| with our replacement. */ |
| if (note != 0 && REG_NOTE_KIND (note) == REG_EQUAL) |
| set_unique_reg_note (insn, REG_EQUAL, |
| simplify_replace_rtx (XEXP (note, 0), from, to)); |
| if (!success && set && reg_mentioned_p (from, SET_SRC (set))) |
| { |
| /* If above failed and this is a single set, try to simplify the source |
| of the set given our substitution. We could perhaps try this for |
| multiple SETs, but it probably won't buy us anything. */ |
| src = simplify_replace_rtx (SET_SRC (set), from, to); |
| |
| if (!rtx_equal_p (src, SET_SRC (set)) |
| && validate_change (insn, &SET_SRC (set), src, 0)) |
| success = 1; |
| |
| /* If we've failed perform the replacement, have a single SET to |
| a REG destination and don't yet have a note, add a REG_EQUAL note |
| to not lose information. */ |
| if (!success && note == 0 && set != 0 && REG_P (SET_DEST (set))) |
| note = set_unique_reg_note (insn, REG_EQUAL, copy_rtx (src)); |
| } |
| |
| if (set && MEM_P (SET_DEST (set)) && reg_mentioned_p (from, SET_DEST (set))) |
| { |
| /* Registers can also appear as uses in SET_DEST if it is a MEM. |
| We could perhaps try this for multiple SETs, but it probably |
| won't buy us anything. */ |
| rtx dest = simplify_replace_rtx (SET_DEST (set), from, to); |
| |
| if (!rtx_equal_p (dest, SET_DEST (set)) |
| && validate_change (insn, &SET_DEST (set), dest, 0)) |
| success = 1; |
| } |
| |
| /* REG_EQUAL may get simplified into register. |
| We don't allow that. Remove that note. This code ought |
| not to happen, because previous code ought to synthesize |
| reg-reg move, but be on the safe side. */ |
| if (note && REG_NOTE_KIND (note) == REG_EQUAL && REG_P (XEXP (note, 0))) |
| remove_note (insn, note); |
| |
| return success; |
| } |
| |
| /* Find a set of REGNOs that are available on entry to INSN's block. Return |
| NULL no such set is found. */ |
| |
| static struct cprop_expr * |
| find_avail_set (int regno, rtx_insn *insn) |
| { |
| /* SET1 contains the last set found that can be returned to the caller for |
| use in a substitution. */ |
| struct cprop_expr *set1 = 0; |
| |
| /* Loops are not possible here. To get a loop we would need two sets |
| available at the start of the block containing INSN. i.e. we would |
| need two sets like this available at the start of the block: |
| |
| (set (reg X) (reg Y)) |
| (set (reg Y) (reg X)) |
| |
| This can not happen since the set of (reg Y) would have killed the |
| set of (reg X) making it unavailable at the start of this block. */ |
| while (1) |
| { |
| rtx src; |
| struct cprop_expr *set = lookup_set (regno, &set_hash_table); |
| |
| /* Find a set that is available at the start of the block |
| which contains INSN. */ |
| while (set) |
| { |
| if (bitmap_bit_p (cprop_avin[BLOCK_FOR_INSN (insn)->index], |
| set->bitmap_index)) |
| break; |
| set = next_set (regno, set); |
| } |
| |
| /* If no available set was found we've reached the end of the |
| (possibly empty) copy chain. */ |
| if (set == 0) |
| break; |
| |
| src = set->src; |
| |
| /* We know the set is available. |
| Now check that SRC is locally anticipatable (i.e. none of the |
| source operands have changed since the start of the block). |
| |
| If the source operand changed, we may still use it for the next |
| iteration of this loop, but we may not use it for substitutions. */ |
| |
| if (cprop_constant_p (src) || reg_not_set_p (src, insn)) |
| set1 = set; |
| |
| /* If the source of the set is anything except a register, then |
| we have reached the end of the copy chain. */ |
| if (! REG_P (src)) |
| break; |
| |
| /* Follow the copy chain, i.e. start another iteration of the loop |
| and see if we have an available copy into SRC. */ |
| regno = REGNO (src); |
| } |
| |
| /* SET1 holds the last set that was available and anticipatable at |
| INSN. */ |
| return set1; |
| } |
| |
| /* Subroutine of cprop_insn that tries to propagate constants into |
| JUMP_INSNS. JUMP must be a conditional jump. If SETCC is non-NULL |
| it is the instruction that immediately precedes JUMP, and must be a |
| single SET of a register. FROM is what we will try to replace, |
| SRC is the constant we will try to substitute for it. Return nonzero |
| if a change was made. */ |
| |
| static int |
| cprop_jump (basic_block bb, rtx_insn *setcc, rtx_insn *jump, rtx from, rtx src) |
| { |
| rtx new_rtx, set_src, note_src; |
| rtx set = pc_set (jump); |
| rtx note = find_reg_equal_equiv_note (jump); |
| |
| if (note) |
| { |
| note_src = XEXP (note, 0); |
| if (GET_CODE (note_src) == EXPR_LIST) |
| note_src = NULL_RTX; |
| } |
| else note_src = NULL_RTX; |
| |
| /* Prefer REG_EQUAL notes except those containing EXPR_LISTs. */ |
| set_src = note_src ? note_src : SET_SRC (set); |
| |
| /* First substitute the SETCC condition into the JUMP instruction, |
| then substitute that given values into this expanded JUMP. */ |
| if (setcc != NULL_RTX |
| && !modified_between_p (from, setcc, jump) |
| && !modified_between_p (src, setcc, jump)) |
| { |
| rtx setcc_src; |
| rtx setcc_set = single_set (setcc); |
| rtx setcc_note = find_reg_equal_equiv_note (setcc); |
| setcc_src = (setcc_note && GET_CODE (XEXP (setcc_note, 0)) != EXPR_LIST) |
| ? XEXP (setcc_note, 0) : SET_SRC (setcc_set); |
| set_src = simplify_replace_rtx (set_src, SET_DEST (setcc_set), |
| setcc_src); |
| } |
| else |
| setcc = NULL; |
| |
| new_rtx = simplify_replace_rtx (set_src, from, src); |
| |
| /* If no simplification can be made, then try the next register. */ |
| if (rtx_equal_p (new_rtx, SET_SRC (set))) |
| return 0; |
| |
| /* If this is now a no-op delete it, otherwise this must be a valid insn. */ |
| if (new_rtx == pc_rtx) |
| delete_insn (jump); |
| else |
| { |
| /* Ensure the value computed inside the jump insn to be equivalent |
| to one computed by setcc. */ |
| if (setcc && modified_in_p (new_rtx, setcc)) |
| return 0; |
| if (! validate_unshare_change (jump, &SET_SRC (set), new_rtx, 0)) |
| { |
| /* When (some) constants are not valid in a comparison, and there |
| are two registers to be replaced by constants before the entire |
| comparison can be folded into a constant, we need to keep |
| intermediate information in REG_EQUAL notes. For targets with |
| separate compare insns, such notes are added by try_replace_reg. |
| When we have a combined compare-and-branch instruction, however, |
| we need to attach a note to the branch itself to make this |
| optimization work. */ |
| |
| if (!rtx_equal_p (new_rtx, note_src)) |
| set_unique_reg_note (jump, REG_EQUAL, copy_rtx (new_rtx)); |
| return 0; |
| } |
| |
| /* Remove REG_EQUAL note after simplification. */ |
| if (note_src) |
| remove_note (jump, note); |
| } |
| |
| #ifdef HAVE_cc0 |
| /* Delete the cc0 setter. */ |
| if (setcc != NULL && CC0_P (SET_DEST (single_set (setcc)))) |
| delete_insn (setcc); |
| #endif |
| |
| global_const_prop_count++; |
| if (dump_file != NULL) |
| { |
| fprintf (dump_file, |
| "GLOBAL CONST-PROP: Replacing reg %d in jump_insn %d with" |
| "constant ", REGNO (from), INSN_UID (jump)); |
| print_rtl (dump_file, src); |
| fprintf (dump_file, "\n"); |
| } |
| purge_dead_edges (bb); |
| |
| /* If a conditional jump has been changed into unconditional jump, remove |
| the jump and make the edge fallthru - this is always called in |
| cfglayout mode. */ |
| if (new_rtx != pc_rtx && simplejump_p (jump)) |
| { |
| edge e; |
| edge_iterator ei; |
| |
| FOR_EACH_EDGE (e, ei, bb->succs) |
| if (e->dest != EXIT_BLOCK_PTR_FOR_FN (cfun) |
| && BB_HEAD (e->dest) == JUMP_LABEL (jump)) |
| { |
| e->flags |= EDGE_FALLTHRU; |
| break; |
| } |
| delete_insn (jump); |
| } |
| |
| return 1; |
| } |
| |
| /* Subroutine of cprop_insn that tries to propagate constants. FROM is what |
| we will try to replace, SRC is the constant we will try to substitute for |
| it and INSN is the instruction where this will be happening. */ |
| |
| static int |
| constprop_register (rtx from, rtx src, rtx_insn *insn) |
| { |
| rtx sset; |
| |
| /* Check for reg or cc0 setting instructions followed by |
| conditional branch instructions first. */ |
| if ((sset = single_set (insn)) != NULL |
| && NEXT_INSN (insn) |
| && any_condjump_p (NEXT_INSN (insn)) && onlyjump_p (NEXT_INSN (insn))) |
| { |
| rtx dest = SET_DEST (sset); |
| if ((REG_P (dest) || CC0_P (dest)) |
| && cprop_jump (BLOCK_FOR_INSN (insn), insn, NEXT_INSN (insn), |
| from, src)) |
| return 1; |
| } |
| |
| /* Handle normal insns next. */ |
| if (NONJUMP_INSN_P (insn) && try_replace_reg (from, src, insn)) |
| return 1; |
| |
| /* Try to propagate a CONST_INT into a conditional jump. |
| We're pretty specific about what we will handle in this |
| code, we can extend this as necessary over time. |
| |
| Right now the insn in question must look like |
| (set (pc) (if_then_else ...)) */ |
| else if (any_condjump_p (insn) && onlyjump_p (insn)) |
| return cprop_jump (BLOCK_FOR_INSN (insn), NULL, insn, from, src); |
| return 0; |
| } |
| |
| /* Perform constant and copy propagation on INSN. |
| Return nonzero if a change was made. */ |
| |
| static int |
| cprop_insn (rtx_insn *insn) |
| { |
| unsigned i; |
| int changed = 0, changed_this_round; |
| rtx note; |
| |
| retry: |
| changed_this_round = 0; |
| reg_use_count = 0; |
| note_uses (&PATTERN (insn), find_used_regs, NULL); |
| |
| /* We may win even when propagating constants into notes. */ |
| note = find_reg_equal_equiv_note (insn); |
| if (note) |
| find_used_regs (&XEXP (note, 0), NULL); |
| |
| for (i = 0; i < reg_use_count; i++) |
| { |
| rtx reg_used = reg_use_table[i]; |
| unsigned int regno = REGNO (reg_used); |
| rtx src; |
| struct cprop_expr *set; |
| |
| /* If the register has already been set in this block, there's |
| nothing we can do. */ |
| if (! reg_not_set_p (reg_used, insn)) |
| continue; |
| |
| /* Find an assignment that sets reg_used and is available |
| at the start of the block. */ |
| set = find_avail_set (regno, insn); |
| if (! set) |
| continue; |
| |
| src = set->src; |
| |
| /* Constant propagation. */ |
| if (cprop_constant_p (src)) |
| { |
| if (constprop_register (reg_used, src, insn)) |
| { |
| changed_this_round = changed = 1; |
| global_const_prop_count++; |
| if (dump_file != NULL) |
| { |
| fprintf (dump_file, |
| "GLOBAL CONST-PROP: Replacing reg %d in ", regno); |
| fprintf (dump_file, "insn %d with constant ", |
| INSN_UID (insn)); |
| print_rtl (dump_file, src); |
| fprintf (dump_file, "\n"); |
| } |
| if (insn->deleted ()) |
| return 1; |
| } |
| } |
| else if (REG_P (src) |
| && REGNO (src) >= FIRST_PSEUDO_REGISTER |
| && REGNO (src) != regno) |
| { |
| if (try_replace_reg (reg_used, src, insn)) |
| { |
| changed_this_round = changed = 1; |
| global_copy_prop_count++; |
| if (dump_file != NULL) |
| { |
| fprintf (dump_file, |
| "GLOBAL COPY-PROP: Replacing reg %d in insn %d", |
| regno, INSN_UID (insn)); |
| fprintf (dump_file, " with reg %d\n", REGNO (src)); |
| } |
| |
| /* The original insn setting reg_used may or may not now be |
| deletable. We leave the deletion to DCE. */ |
| /* FIXME: If it turns out that the insn isn't deletable, |
| then we may have unnecessarily extended register lifetimes |
| and made things worse. */ |
| } |
| } |
| |
| /* If try_replace_reg simplified the insn, the regs found |
| by find_used_regs may not be valid anymore. Start over. */ |
| if (changed_this_round) |
| goto retry; |
| } |
| |
| if (changed && DEBUG_INSN_P (insn)) |
| return 0; |
| |
| return changed; |
| } |
| |
| /* Like find_used_regs, but avoid recording uses that appear in |
| input-output contexts such as zero_extract or pre_dec. This |
| restricts the cases we consider to those for which local cprop |
| can legitimately make replacements. */ |
| |
| static void |
| local_cprop_find_used_regs (rtx *xptr, void *data) |
| { |
| rtx x = *xptr; |
| |
| if (x == 0) |
| return; |
| |
| switch (GET_CODE (x)) |
| { |
| case ZERO_EXTRACT: |
| case SIGN_EXTRACT: |
| case STRICT_LOW_PART: |
| return; |
| |
| case PRE_DEC: |
| case PRE_INC: |
| case POST_DEC: |
| case POST_INC: |
| case PRE_MODIFY: |
| case POST_MODIFY: |
| /* Can only legitimately appear this early in the context of |
| stack pushes for function arguments, but handle all of the |
| codes nonetheless. */ |
| return; |
| |
| case SUBREG: |
| /* Setting a subreg of a register larger than word_mode leaves |
| the non-written words unchanged. */ |
| if (GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (x))) > BITS_PER_WORD) |
| return; |
| break; |
| |
| default: |
| break; |
| } |
| |
| find_used_regs (xptr, data); |
| } |
| |
| /* Try to perform local const/copy propagation on X in INSN. */ |
| |
| static bool |
| do_local_cprop (rtx x, rtx_insn *insn) |
| { |
| rtx newreg = NULL, newcnst = NULL; |
| |
| /* Rule out USE instructions and ASM statements as we don't want to |
| change the hard registers mentioned. */ |
| if (REG_P (x) |
| && (REGNO (x) >= FIRST_PSEUDO_REGISTER |
| || (GET_CODE (PATTERN (insn)) != USE |
| && asm_noperands (PATTERN (insn)) < 0))) |
| { |
| cselib_val *val = cselib_lookup (x, GET_MODE (x), 0, VOIDmode); |
| struct elt_loc_list *l; |
| |
| if (!val) |
| return false; |
| for (l = val->locs; l; l = l->next) |
| { |
| rtx this_rtx = l->loc; |
| rtx note; |
| |
| if (cprop_constant_p (this_rtx)) |
| newcnst = this_rtx; |
| if (REG_P (this_rtx) && REGNO (this_rtx) >= FIRST_PSEUDO_REGISTER |
| /* Don't copy propagate if it has attached REG_EQUIV note. |
| At this point this only function parameters should have |
| REG_EQUIV notes and if the argument slot is used somewhere |
| explicitly, it means address of parameter has been taken, |
| so we should not extend the lifetime of the pseudo. */ |
| && (!(note = find_reg_note (l->setting_insn, REG_EQUIV, NULL_RTX)) |
| || ! MEM_P (XEXP (note, 0)))) |
| newreg = this_rtx; |
| } |
| if (newcnst && constprop_register (x, newcnst, insn)) |
| { |
| if (dump_file != NULL) |
| { |
| fprintf (dump_file, "LOCAL CONST-PROP: Replacing reg %d in ", |
| REGNO (x)); |
| fprintf (dump_file, "insn %d with constant ", |
| INSN_UID (insn)); |
| print_rtl (dump_file, newcnst); |
| fprintf (dump_file, "\n"); |
| } |
| local_const_prop_count++; |
| return true; |
| } |
| else if (newreg && newreg != x && try_replace_reg (x, newreg, insn)) |
| { |
| if (dump_file != NULL) |
| { |
| fprintf (dump_file, |
| "LOCAL COPY-PROP: Replacing reg %d in insn %d", |
| REGNO (x), INSN_UID (insn)); |
| fprintf (dump_file, " with reg %d\n", REGNO (newreg)); |
| } |
| local_copy_prop_count++; |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| /* Do local const/copy propagation (i.e. within each basic block). */ |
| |
| static int |
| local_cprop_pass (void) |
| { |
| basic_block bb; |
| rtx_insn *insn; |
| bool changed = false; |
| unsigned i; |
| |
| cselib_init (0); |
| FOR_EACH_BB_FN (bb, cfun) |
| { |
| FOR_BB_INSNS (bb, insn) |
| { |
| if (INSN_P (insn)) |
| { |
| rtx note = find_reg_equal_equiv_note (insn); |
| do |
| { |
| reg_use_count = 0; |
| note_uses (&PATTERN (insn), local_cprop_find_used_regs, |
| NULL); |
| if (note) |
| local_cprop_find_used_regs (&XEXP (note, 0), NULL); |
| |
| for (i = 0; i < reg_use_count; i++) |
| { |
| if (do_local_cprop (reg_use_table[i], insn)) |
| { |
| if (!DEBUG_INSN_P (insn)) |
| changed = true; |
| break; |
| } |
| } |
| if (insn->deleted ()) |
| break; |
| } |
| while (i < reg_use_count); |
| } |
| cselib_process_insn (insn); |
| } |
| |
| /* Forget everything at the end of a basic block. */ |
| cselib_clear_table (); |
| } |
| |
| cselib_finish (); |
| |
| return changed; |
| } |
| |
| /* Similar to get_condition, only the resulting condition must be |
| valid at JUMP, instead of at EARLIEST. |
| |
| This differs from noce_get_condition in ifcvt.c in that we prefer not to |
| settle for the condition variable in the jump instruction being integral. |
| We prefer to be able to record the value of a user variable, rather than |
| the value of a temporary used in a condition. This could be solved by |
| recording the value of *every* register scanned by canonicalize_condition, |
| but this would require some code reorganization. */ |
| |
| rtx |
| fis_get_condition (rtx_insn *jump) |
| { |
| return get_condition (jump, NULL, false, true); |
| } |
| |
| /* 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) |
| { |
| 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. */ |
| if (HONOR_SIGNED_ZEROS (mode)) |
| { |
| /* It is sufficient to check if CST is or contains a zero. We must |
| handle float, complex, and vector. If any subpart is a zero, then |
| the optimization can't be performed. */ |
| /* ??? The complex and vector checks are not implemented yet. We just |
| always return zero for them. */ |
| if (CONST_DOUBLE_AS_FLOAT_P (cst)) |
| { |
| REAL_VALUE_TYPE d; |
| REAL_VALUE_FROM_CONST_DOUBLE (d, cst); |
| if (REAL_VALUES_EQUAL (d, dconst0)) |
| return 0; |
| } |
| else |
| return 0; |
| } |
| |
| return cprop_constant_p (cst); |
| } |
| |
| /* Find the implicit sets of a function. An "implicit set" is a constraint |
| on the value of a variable, implied by a conditional jump. For example, |
| following "if (x == 2)", the then branch may be optimized as though the |
| conditional performed an "explicit set", in this example, "x = 2". This |
| function records the set patterns that are implicit at the start of each |
| basic block. |
| |
| If an implicit set is found but the set is implicit on a critical edge, |
| this critical edge is split. |
| |
| Return true if the CFG was modified, false otherwise. */ |
| |
| static bool |
| find_implicit_sets (void) |
| { |
| basic_block bb, dest; |
| rtx cond, new_rtx; |
| unsigned int count = 0; |
| bool edges_split = false; |
| size_t implicit_sets_size = last_basic_block_for_fn (cfun) + 10; |
| |
| implicit_sets = XCNEWVEC (rtx, implicit_sets_size); |
| |
| FOR_EACH_BB_FN (bb, cfun) |
| { |
| /* Check for more than one successor. */ |
| if (EDGE_COUNT (bb->succs) <= 1) |
| continue; |
| |
| cond = fis_get_condition (BB_END (bb)); |
| |
| /* 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_FOR_FN (cfun)) |
| 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. */ |
| |
| /* The value of last_basic_block at the beginning of the jump_bypass |
| pass. The use of redirect_edge_and_branch_force may introduce new |
| basic blocks, but the data flow analysis is only valid for basic |
| block indices less than bypass_last_basic_block. */ |
| |
| static int bypass_last_basic_block; |
| |
| /* Find a set of REGNO to a constant that is available at the end of basic |
| block BB. Return NULL if no such set is found. Based heavily upon |
| find_avail_set. */ |
| |
| static struct cprop_expr * |
| find_bypass_set (int regno, int bb) |
| { |
| struct cprop_expr *result = 0; |
| |
| for (;;) |
| { |
| rtx src; |
| struct cprop_expr *set = lookup_set (regno, &set_hash_table); |
| |
| while (set) |
| { |
| if (bitmap_bit_p (cprop_avout[bb], set->bitmap_index)) |
| break; |
| set = next_set (regno, set); |
| } |
| |
| if (set == 0) |
| break; |
| |
| src = set->src; |
| if (cprop_constant_p (src)) |
| result = set; |
| |
| if (! REG_P (src)) |
| break; |
| |
| regno = REGNO (src); |
| } |
| return result; |
| } |
| |
| /* Subroutine of bypass_block that checks whether a pseudo is killed by |
| any of the instructions inserted on an edge. Jump bypassing places |
| condition code setters on CFG edges using insert_insn_on_edge. This |
| function is required to check that our data flow analysis is still |
| valid prior to commit_edge_insertions. */ |
| |
| static bool |
| reg_killed_on_edge (const_rtx reg, const_edge e) |
| { |
| rtx_insn *insn; |
| |
| for (insn = e->insns.r; insn; insn = NEXT_INSN (insn)) |
| if (INSN_P (insn) && reg_set_p (reg, insn)) |
| return true; |
| |
| return false; |
| } |
| |
| /* Subroutine of bypass_conditional_jumps that attempts to bypass the given |
| basic block BB which has more than one predecessor. If not NULL, SETCC |
| is the first instruction of BB, which is immediately followed by JUMP_INSN |
| JUMP. Otherwise, SETCC is NULL, and JUMP is the first insn of BB. |
| Returns nonzero if a change was made. |
| |
| During the jump bypassing pass, we may place copies of SETCC instructions |
| on CFG edges. The following routine must be careful to pay attention to |
| these inserted insns when performing its transformations. */ |
| |
| static int |
| bypass_block (basic_block bb, rtx_insn *setcc, rtx_insn *jump) |
| { |
| rtx_insn *insn; |
| rtx note; |
| edge e, edest; |
| int change; |
| int may_be_loop_header = false; |
| unsigned removed_p; |
| unsigned i; |
| edge_iterator ei; |
| |
| insn = (setcc != NULL) ? setcc : jump; |
| |
| /* Determine set of register uses in INSN. */ |
| reg_use_count = 0; |
| note_uses (&PATTERN (insn), find_used_regs, NULL); |
| note = find_reg_equal_equiv_note (insn); |
| if (note) |
| find_used_regs (&XEXP (note, 0), NULL); |
| |
| if (current_loops) |
| { |
| /* If we are to preserve loop structure then do not bypass |
| a loop header. This will either rotate the loop, create |
| multiple entry loops or even irreducible regions. */ |
| if (bb == bb->loop_father->header) |
| return 0; |
| } |
| else |
| { |
| FOR_EACH_EDGE (e, ei, bb->preds) |
| if (e->flags & EDGE_DFS_BACK) |
| { |
| may_be_loop_header = true; |
| break; |
| } |
| } |
| |
| change = 0; |
| for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei)); ) |
| { |
| removed_p = 0; |
| |
| if (e->flags & EDGE_COMPLEX) |
| { |
| ei_next (&ei); |
| continue; |
| } |
| |
| /* We can't redirect edges from new basic blocks. */ |
| if (e->src->index >= bypass_last_basic_block) |
| { |
| ei_next (&ei); |
| continue; |
| } |
| |
| /* The irreducible loops created by redirecting of edges entering the |
| loop from outside would decrease effectiveness of some of the |
| following optimizations, so prevent this. */ |
| if (may_be_loop_header |
| && !(e->flags & EDGE_DFS_BACK)) |
| { |
| ei_next (&ei); |
| continue; |
| } |
| |
| for (i = 0; i < reg_use_count; i++) |
| { |
| rtx reg_used = reg_use_table[i]; |
| unsigned int regno = REGNO (reg_used); |
| basic_block dest, old_dest; |
| struct cprop_expr *set; |
| rtx src, new_rtx; |
| |
| set = find_bypass_set (regno, e->src->index); |
| |
| if (! set) |
| continue; |
| |
| /* Check the data flow is valid after edge insertions. */ |
| if (e->insns.r && reg_killed_on_edge (reg_used, e)) |
| continue; |
| |
| src = SET_SRC (pc_set (jump)); |
| |
| if (setcc != NULL) |
| src = simplify_replace_rtx (src, |
| SET_DEST (PATTERN (setcc)), |
| SET_SRC (PATTERN (setcc))); |
| |
| new_rtx = simplify_replace_rtx (src, reg_used, set->src); |
| |
| /* Jump bypassing may have already placed instructions on |
| edges of the CFG. We can't bypass an outgoing edge that |
| has instructions associated with it, as these insns won't |
| get executed if the incoming edge is redirected. */ |
| if (new_rtx == pc_rtx) |
| { |
| edest = FALLTHRU_EDGE (bb); |
| dest = edest->insns.r ? NULL : edest->dest; |
| } |
| else if (GET_CODE (new_rtx) == LABEL_REF) |
| { |
| dest = BLOCK_FOR_INSN (XEXP (new_rtx, 0)); |
| /* Don't bypass edges containing instructions. */ |
| edest = find_edge (bb, dest); |
| if (edest && edest->insns.r) |
| dest = NULL; |
| } |
| else |
| dest = NULL; |
| |
| /* Avoid unification of the edge with other edges from original |
| branch. We would end up emitting the instruction on "both" |
| edges. */ |
| if (dest && setcc && !CC0_P (SET_DEST (PATTERN (setcc))) |
| && find_edge (e->src, dest)) |
| dest = NULL; |
| |
| old_dest = e->dest; |
| if (dest != NULL |
| && dest != old_dest |
| && dest != EXIT_BLOCK_PTR_FOR_FN (cfun)) |
| { |
| redirect_edge_and_branch_force (e, dest); |
| |
| /* Copy the register setter to the redirected edge. |
| Don't copy CC0 setters, as CC0 is dead after jump. */ |
| if (setcc) |
| { |
| rtx pat = PATTERN (setcc); |
| if (!CC0_P (SET_DEST (pat))) |
| insert_insn_on_edge (copy_insn (pat), e); |
| } |
| |
| if (dump_file != NULL) |
| { |
| fprintf (dump_file, "JUMP-BYPASS: Proved reg %d " |
| "in jump_insn %d equals constant ", |
| regno, INSN_UID (jump)); |
| print_rtl (dump_file, set->src); |
| fprintf (dump_file, "\n\t when BB %d is entered from " |
| "BB %d. Redirect edge %d->%d to %d.\n", |
| old_dest->index, e->src->index, e->src->index, |
| old_dest->index, dest->index); |
| } |
| change = 1; |
| removed_p = 1; |
| break; |
| } |
| } |
| if (!removed_p) |
| ei_next (&ei); |
| } |
| return change; |
| } |
| |
| /* Find basic blocks with more than one predecessor that only contain a |
| single conditional jump. If the result of the comparison is known at |
| compile-time from any incoming edge, redirect that edge to the |
| appropriate target. Return nonzero if a change was made. |
| |
| This function is now mis-named, because we also handle indirect jumps. */ |
| |
| static int |
| bypass_conditional_jumps (void) |
| { |
| basic_block bb; |
| int changed; |
| rtx_insn *setcc; |
| rtx_insn *insn; |
| rtx dest; |
| |
| /* Note we start at block 1. */ |
| if (ENTRY_BLOCK_PTR_FOR_FN (cfun)->next_bb == EXIT_BLOCK_PTR_FOR_FN (cfun)) |
| return 0; |
| |
| bypass_last_basic_block = last_basic_block_for_fn (cfun); |
| mark_dfs_back_edges (); |
| |
| changed = 0; |
| FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR_FOR_FN (cfun)->next_bb->next_bb, |
| EXIT_BLOCK_PTR_FOR_FN (cfun), next_bb) |
| { |
| /* Check for more than one predecessor. */ |
| if (!single_pred_p (bb)) |
| { |
| setcc = NULL; |
| FOR_BB_INSNS (bb, insn) |
| if (DEBUG_INSN_P (insn)) |
| continue; |
| else if (NONJUMP_INSN_P (insn)) |
| { |
| if (setcc) |
| break; |
| if (GET_CODE (PATTERN (insn)) != SET) |
| break; |
| |
| dest = SET_DEST (PATTERN (insn)); |
| if (REG_P (dest) || CC0_P (dest)) |
| setcc = insn; |
| else |
| break; |
| } |
| else if (JUMP_P (insn)) |
| { |
| if ((any_condjump_p (insn) || computed_jump_p (insn)) |
| && onlyjump_p (insn)) |
| changed |= bypass_block (bb, setcc, insn); |
| break; |
| } |
| else if (INSN_P (insn)) |
| break; |
| } |
| } |
| |
| /* If we bypassed any register setting insns, we inserted a |
| copy on the redirected edge. These need to be committed. */ |
| if (changed) |
| commit_edge_insertions (); |
| |
| return changed; |
| } |
| |
| /* Return true if the graph is too expensive to optimize. PASS is the |
| optimization about to be performed. */ |
| |
| static bool |
| is_too_expensive (const char *pass) |
| { |
| /* Trying to perform global optimizations on flow graphs which have |
| a high connectivity will take a long time and is unlikely to be |
| particularly useful. |
| |
| In normal circumstances a cfg should have about twice as many |
| edges as blocks. But we do not want to punish small functions |
| which have a couple switch statements. Rather than simply |
| threshold the number of blocks, uses something with a more |
| graceful degradation. */ |
| if (n_edges_for_fn (cfun) > 20000 + n_basic_blocks_for_fn (cfun) * 4) |
| { |
| warning (OPT_Wdisabled_optimization, |
| "%s: %d basic blocks and %d edges/basic block", |
| pass, n_basic_blocks_for_fn (cfun), |
| n_edges_for_fn (cfun) / n_basic_blocks_for_fn (cfun)); |
| |
| return true; |
| } |
| |
| /* If allocating memory for the cprop bitmap would take up too much |
| storage it's better just to disable the optimization. */ |
| if ((n_basic_blocks_for_fn (cfun) |
| * SBITMAP_SET_SIZE (max_reg_num ()) |
| * sizeof (SBITMAP_ELT_TYPE)) > MAX_GCSE_MEMORY) |
| { |
| warning (OPT_Wdisabled_optimization, |
| "%s: %d basic blocks and %d registers", |
| pass, n_basic_blocks_for_fn (cfun), max_reg_num ()); |
| |
| return true; |
| } |
| |
| return false; |
| } |
| |
| /* Main function for the CPROP pass. */ |
| |
| static int |
| one_cprop_pass (void) |
| { |
| int i; |
| int changed = 0; |
| |
| /* Return if there's nothing to do, or it is too expensive. */ |
| if (n_basic_blocks_for_fn (cfun) <= NUM_FIXED_BLOCKS + 1 |
| || is_too_expensive (_ ("const/copy propagation disabled"))) |
| return 0; |
| |
| global_const_prop_count = local_const_prop_count = 0; |
| global_copy_prop_count = local_copy_prop_count = 0; |
| |
| bytes_used = 0; |
| gcc_obstack_init (&cprop_obstack); |
| |
| /* Do a local const/copy propagation pass first. The global pass |
| only handles global opportunities. |
| If the local pass changes something, remove any unreachable blocks |
| because the CPROP global dataflow analysis may get into infinite |
| loops for CFGs with unreachable blocks. |
| |
| FIXME: This local pass should not be necessary after CSE (but for |
| some reason it still is). It is also (proven) not necessary |
| to run the local pass right after FWPWOP. |
| |
| FIXME: The global analysis would not get into infinite loops if it |
| would use the DF solver (via df_simple_dataflow) instead of |
| the solver implemented in this file. */ |
| changed |= local_cprop_pass (); |
| if (changed) |
| 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 (); |
| |
| /* Initialize implicit_set_indexes array. */ |
| implicit_set_indexes = XNEWVEC (int, last_basic_block_for_fn (cfun)); |
| for (i = 0; i < last_basic_block_for_fn (cfun); i++) |
| implicit_set_indexes[i] = -1; |
| |
| alloc_hash_table (&set_hash_table); |
| compute_hash_table (&set_hash_table); |
| |
| /* Free implicit_sets before peak usage. */ |
| free (implicit_sets); |
| implicit_sets = NULL; |
| |
| if (dump_file) |
| dump_hash_table (dump_file, "SET", &set_hash_table); |
| if (set_hash_table.n_elems > 0) |
| { |
| basic_block bb; |
| rtx_insn *insn; |
| |
| alloc_cprop_mem (last_basic_block_for_fn (cfun), |
| set_hash_table.n_elems); |
| compute_cprop_data (); |
| |
| free (implicit_set_indexes); |
| implicit_set_indexes = NULL; |
| |
| /* Allocate vars to track sets of regs. */ |
| reg_set_bitmap = ALLOC_REG_SET (NULL); |
| |
| FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR_FOR_FN (cfun)->next_bb->next_bb, |
| EXIT_BLOCK_PTR_FOR_FN (cfun), |
| next_bb) |
| { |
| /* Reset tables used to keep track of what's still valid [since |
| the start of the block]. */ |
| reset_opr_set_tables (); |
| |
| FOR_BB_INSNS (bb, insn) |
| if (INSN_P (insn)) |
| { |
| changed |= cprop_insn (insn); |
| |
| /* Keep track of everything modified by this insn. */ |
| /* ??? Need to be careful w.r.t. mods done to INSN. |
| Don't call mark_oprs_set if we turned the |
| insn into a NOTE, or deleted the insn. */ |
| if (! NOTE_P (insn) && ! insn->deleted ()) |
| mark_oprs_set (insn); |
| } |
| } |
| |
| changed |= bypass_conditional_jumps (); |
| |
| FREE_REG_SET (reg_set_bitmap); |
| free_cprop_mem (); |
| } |
| else |
| { |
| free (implicit_set_indexes); |
| implicit_set_indexes = NULL; |
| } |
| |
| free_hash_table (&set_hash_table); |
| obstack_free (&cprop_obstack, NULL); |
| |
| if (dump_file) |
| { |
| fprintf (dump_file, "CPROP of %s, %d basic blocks, %d bytes needed, ", |
| current_function_name (), n_basic_blocks_for_fn (cfun), |
| bytes_used); |
| fprintf (dump_file, "%d local const props, %d local copy props, ", |
| local_const_prop_count, local_copy_prop_count); |
| fprintf (dump_file, "%d global const props, %d global copy props\n\n", |
| global_const_prop_count, global_copy_prop_count); |
| } |
| |
| return changed; |
| } |
| |
| /* All the passes implemented in this file. Each pass has its |
| own gate and execute function, and at the end of the file a |
| pass definition for passes.c. |
| |
| We do not construct an accurate cfg in functions which call |
| setjmp, so none of these passes runs if the function calls |
| setjmp. |
| FIXME: Should just handle setjmp via REG_SETJMP notes. */ |
| |
| static unsigned int |
| execute_rtl_cprop (void) |
| { |
| int changed; |
| delete_unreachable_blocks (); |
| df_set_flags (DF_LR_RUN_DCE); |
| df_analyze (); |
| changed = one_cprop_pass (); |
| flag_rerun_cse_after_global_opts |= changed; |
| if (changed) |
| cleanup_cfg (CLEANUP_CFG_CHANGED); |
| return 0; |
| } |
| |
| namespace { |
| |
| const pass_data pass_data_rtl_cprop = |
| { |
| RTL_PASS, /* type */ |
| "cprop", /* name */ |
| OPTGROUP_NONE, /* optinfo_flags */ |
| TV_CPROP, /* tv_id */ |
| PROP_cfglayout, /* properties_required */ |
| 0, /* properties_provided */ |
| 0, /* properties_destroyed */ |
| 0, /* todo_flags_start */ |
| TODO_df_finish, /* todo_flags_finish */ |
| }; |
| |
| class pass_rtl_cprop : public rtl_opt_pass |
| { |
| public: |
| pass_rtl_cprop (gcc::context *ctxt) |
| : rtl_opt_pass (pass_data_rtl_cprop, ctxt) |
| {} |
| |
| /* opt_pass methods: */ |
| opt_pass * clone () { return new pass_rtl_cprop (m_ctxt); } |
| virtual bool gate (function *fun) |
| { |
| return optimize > 0 && flag_gcse |
| && !fun->calls_setjmp |
| && dbg_cnt (cprop); |
| } |
| |
| virtual unsigned int execute (function *) { return execute_rtl_cprop (); } |
| |
| }; // class pass_rtl_cprop |
| |
| } // anon namespace |
| |
| rtl_opt_pass * |
| make_pass_rtl_cprop (gcc::context *ctxt) |
| { |
| return new pass_rtl_cprop (ctxt); |
| } |