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 2, or (at your option) any later
+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
for more details.
You should have received a copy of the GNU General Public License
-along with GCC; see the file COPYING. If not, write to the Free
-Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
-02110-1301, USA. */
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
#include "config.h"
#include "system.h"
Core mark/delete routines
------------------------------------------------------------------------- */
-/* The data-flow information needed by this pass. */
+/* True if we are invoked while the df engine is running; in this case,
+ we don't want to reenter it. */
static bool df_in_progress = false;
-/* True if we deleted at least one instruction. */
-static bool something_changed;
-
/* Instructions that have been marked but whose dependencies have not
yet been processed. */
static VEC(rtx,heap) *worklist;
+/* Bitmap of instructions marked as needed indexed by INSN_UID. */
+static sbitmap marked;
+
+/* Bitmap obstacks used for block processing by the fast algorithm. */
static bitmap_obstack dce_blocks_bitmap_obstack;
static bitmap_obstack dce_tmp_bitmap_obstack;
-static sbitmap marked = NULL;
/* A subroutine for which BODY is part of the instruction being tested;
either the top-level pattern, or an element of a PARALLEL. The
return false;
default:
- if (volatile_insn_p (body))
+ if (volatile_refs_p (body))
return false;
if (flag_non_call_exceptions && may_trap_p (body))
}
}
+
/* Return true if INSN is a normal instruction that can be deleted by
the DCE pass. */
}
-/* Return true if INSN has not been marked as needed. */
+/* Return true if INSN has been marked as needed. */
static inline int
marked_insn_p (rtx insn)
instruction containing DEST. */
static void
-mark_nonreg_stores_1 (rtx dest, rtx pattern, void *data)
+mark_nonreg_stores_1 (rtx dest, const_rtx pattern, void *data)
{
if (GET_CODE (pattern) != CLOBBER && !REG_P (dest))
mark_insn ((rtx) data, true);
instruction containing DEST. */
static void
-mark_nonreg_stores_2 (rtx dest, rtx pattern, void *data)
+mark_nonreg_stores_2 (rtx dest, const_rtx pattern, void *data)
{
if (GET_CODE (pattern) != CLOBBER && !REG_P (dest))
mark_insn ((rtx) data, false);
}
-/* Initialize global variables for a new DCE pass. */
+/* Return true if the entire libcall sequence starting at INSN is dead.
+ NOTE is the REG_LIBCALL note attached to INSN.
-static void
-init_dce (bool fast)
+ A libcall sequence is a block of insns with no side-effects, i.e.
+ that is only used for its return value. The terminology derives
+ from that of a call, but a libcall sequence need not contain one.
+ It is only defined by a pair of REG_LIBCALL/REG_RETVAL notes.
+
+ From a dataflow viewpoint, a libcall sequence has the property that
+ no UD chain can enter it from the outside. As a consequence, if a
+ libcall sequence has a dead return value, it is effectively dead.
+ This is both enforced by CSE (cse_extended_basic_block) and relied
+ upon by delete_trivially_dead_insns.
+
+ However, in practice, the return value business is a tricky one and
+ only checking the liveness of the last insn is not sufficient to
+ decide whether the whole sequence is dead (e.g. PR middle-end/19551)
+ so we check the liveness of every insn starting from the call. */
+
+static bool
+libcall_dead_p (rtx insn, rtx note)
{
- if (!df_in_progress)
+ rtx last = XEXP (note, 0);
+
+ /* Find the call insn. */
+ while (insn != last && !CALL_P (insn))
+ insn = NEXT_INSN (insn);
+
+ /* If there is none, do nothing special, since ordinary death handling
+ can understand these insns. */
+ if (!CALL_P (insn))
+ return false;
+
+ /* If this is a call that returns a value via an invisible pointer, the
+ dataflow engine cannot see it so it has been marked unconditionally.
+ Skip it unless it has been made the last insn in the libcall, for
+ example by the combiner, in which case we're left with no easy way
+ of asserting its liveness. */
+ if (!single_set (insn))
{
- if (!fast)
- df_chain_add_problem (DF_UD_CHAIN);
- df_analyze ();
+ if (insn == last)
+ return false;
+ insn = NEXT_INSN (insn);
}
- if (dump_file)
- df_dump (dump_file);
+ while (insn != NEXT_INSN (last))
+ {
+ if (INSN_P (insn) && marked_insn_p (insn))
+ return false;
+ insn = NEXT_INSN (insn);
+ }
- bitmap_obstack_initialize (&dce_blocks_bitmap_obstack);
- bitmap_obstack_initialize (&dce_tmp_bitmap_obstack);
- marked = sbitmap_alloc (get_max_uid () + 1);
- sbitmap_zero (marked);
+ return true;
}
}
-/* Delete every instruction that hasn't been marked. Clear the insn
- from DCE_DF if DF_DELETE is true. */
+/* Delete every instruction that hasn't been marked. */
static void
delete_unmarked_insns (void)
basic_block bb;
rtx insn, next;
- something_changed = false;
FOR_EACH_BB (bb)
FOR_BB_INSNS_SAFE (bb, insn, next)
if (INSN_P (insn))
{
+ rtx note = find_reg_note (insn, REG_LIBCALL, NULL_RTX);
+
+ /* Always delete no-op moves. */
if (noop_move_p (insn))
+ ;
+
+ /* Try to delete libcall sequences as a whole. */
+ else if (note && libcall_dead_p (insn, note))
{
- /* Note that this code does not handle the case where
- the last insn of libcall is deleted. As it turns out
- this case is excluded in the call to noop_move_p. */
- rtx note = find_reg_note (insn, REG_LIBCALL, NULL_RTX);
- if (note && (XEXP (note, 0) != insn))
- {
- rtx new_libcall_insn = next_real_insn (insn);
- rtx retval_note = find_reg_note (XEXP (note, 0),
- REG_RETVAL, NULL_RTX);
- REG_NOTES (new_libcall_insn)
- = gen_rtx_INSN_LIST (REG_LIBCALL, XEXP (note, 0),
- REG_NOTES (new_libcall_insn));
- XEXP (retval_note, 0) = new_libcall_insn;
- }
+ rtx last = XEXP (note, 0);
+
+ if (!dbg_cnt (dce))
+ continue;
+
+ if (dump_file)
+ fprintf (dump_file, "DCE: Deleting libcall %d-%d\n",
+ INSN_UID (insn), INSN_UID (last));
+
+ next = NEXT_INSN (last);
+ delete_insn_chain_and_edges (insn, last);
+ continue;
}
+
+ /* Otherwise rely only on the DCE algorithm. */
else if (marked_insn_p (insn))
continue;
- /* WARNING, this debugging can itself cause problems if the
- edge of the counter causes part of a libcall to be
- deleted but not all of it. */
if (!dbg_cnt (dce))
continue;
if (dump_file)
fprintf (dump_file, "DCE: Deleting insn %d\n", INSN_UID (insn));
- /* Before we delete the insn, we have to delete
- REG_EQUAL of the destination regs of the deleted insn
- to prevent dangling REG_EQUAL. */
- delete_corresponding_reg_eq_notes (insn);
+ /* Before we delete the insn we have to delete REG_EQUAL notes
+ for the destination regs in order to avoid dangling notes. */
+ delete_corresponding_reg_eq_notes (insn);
+ /* If we're about to delete the first insn of a libcall, then
+ move the REG_LIBCALL note to the next real insn and update
+ the REG_RETVAL note. */
+ if (note && (XEXP (note, 0) != insn))
+ {
+ rtx new_libcall_insn = next_real_insn (insn);
+ rtx retval_note = find_reg_note (XEXP (note, 0),
+ REG_RETVAL, NULL_RTX);
+ /* If the RETVAL and LIBCALL notes would land on the same
+ insn just remove them. */
+ if (XEXP (note, 0) == new_libcall_insn)
+ remove_note (new_libcall_insn, retval_note);
+ else
+ {
+ REG_NOTES (new_libcall_insn)
+ = gen_rtx_INSN_LIST (REG_LIBCALL, XEXP (note, 0),
+ REG_NOTES (new_libcall_insn));
+ XEXP (retval_note, 0) = new_libcall_insn;
+ }
+ }
+
+ /* If the insn contains a REG_RETVAL note and is dead, but the
+ libcall as a whole is not dead, then we want to remove the
+ insn, but not the whole libcall sequence. However, we also
+ need to remove the dangling REG_LIBCALL note in order to
+ avoid mismatched notes. We could find a new location for
+ the REG_RETVAL note, but it hardly seems worth the effort. */
+ note = find_reg_note (insn, REG_RETVAL, NULL_RTX);
+ if (note && (XEXP (note, 0) != insn))
+ {
+ rtx libcall_note
+ = find_reg_note (XEXP (note, 0), REG_LIBCALL, NULL_RTX);
+ remove_note (XEXP (note, 0), libcall_note);
+ }
+
+ /* Now delete the insn. */
delete_insn_and_edges (insn);
- something_changed = true;
}
}
-/* Mark all insns using DELETE_PARM in the libcall that contains
- START_INSN. */
-static void
-mark_libcall (rtx start_insn, bool delete_parm)
-{
- rtx note = find_reg_note (start_insn, REG_LIBCALL_ID, NULL_RTX);
- int id = INTVAL (XEXP (note, 0));
- rtx insn;
+/* Helper function for prescan_insns_for_dce: prescan the entire libcall
+ sequence starting at INSN and return the insn following the libcall.
+ NOTE is the REG_LIBCALL note attached to INSN. */
- mark_insn (start_insn, delete_parm);
- insn = NEXT_INSN (start_insn);
+static rtx
+prescan_libcall_for_dce (rtx insn, rtx note, bool fast)
+{
+ rtx last = XEXP (note, 0);
- /* There are tales, long ago and far away, of the mystical nested
- libcall. No one alive has actually seen one, but other parts of
- the compiler support them so we will here. */
- for (insn = NEXT_INSN (start_insn); insn; insn = NEXT_INSN (insn))
+ /* A libcall is never necessary on its own but we need to mark the stores
+ to a non-register destination. */
+ while (insn != last && !CALL_P (insn))
{
if (INSN_P (insn))
- {
- /* Stay in the loop as long as we are in any libcall. */
- if ((note = find_reg_note (insn, REG_LIBCALL_ID, NULL_RTX)))
- {
- if (id == INTVAL (XEXP (note, 0)))
- {
- mark_insn (insn, delete_parm);
- if (dump_file)
- fprintf (dump_file, "matching forward libcall %d[%d]\n",
- INSN_UID (insn), id);
- }
- }
- else
- break;
- }
+ mark_nonreg_stores (PATTERN (insn), insn, fast);
+ insn = NEXT_INSN (insn);
}
-
- for (insn = PREV_INSN (start_insn); insn; insn = PREV_INSN (insn))
+
+ /* If this is a call that returns a value via an invisible pointer, the
+ dataflow engine cannot see it so it has to be marked unconditionally. */
+ if (CALL_P (insn) && !single_set (insn))
+ {
+ mark_insn (insn, fast);
+ insn = NEXT_INSN (insn);
+ }
+
+ while (insn != NEXT_INSN (last))
{
if (INSN_P (insn))
- {
- /* Stay in the loop as long as we are in any libcall. */
- if ((note = find_reg_note (insn, REG_LIBCALL_ID, NULL_RTX)))
- {
- if (id == INTVAL (XEXP (note, 0)))
- {
- mark_insn (insn, delete_parm);
- if (dump_file)
- fprintf (dump_file, "matching backward libcall %d[%d]\n",
- INSN_UID (insn), id);
- }
- }
- else
- break;
- }
+ mark_nonreg_stores (PATTERN (insn), insn, fast);
+ insn = NEXT_INSN (insn);
}
+
+ return insn;
}
prescan_insns_for_dce (bool fast)
{
basic_block bb;
- rtx insn;
+ rtx insn, next;
if (dump_file)
fprintf (dump_file, "Finding needed instructions:\n");
FOR_EACH_BB (bb)
- FOR_BB_INSNS (bb, insn)
- if (INSN_P (insn))
- {
- rtx note = find_reg_note (insn, REG_LIBCALL_ID, NULL_RTX);
- if (note)
- mark_libcall (insn, fast);
- else if (deletable_insn_p (insn, fast))
- mark_nonreg_stores (PATTERN (insn), insn, fast);
- else
- mark_insn (insn, fast);
- }
+ FOR_BB_INSNS_SAFE (bb, insn, next)
+ if (INSN_P (insn))
+ {
+ rtx note = find_reg_note (insn, REG_LIBCALL, NULL_RTX);
+ if (note)
+ next = prescan_libcall_for_dce (insn, note, fast);
+ else if (deletable_insn_p (insn, fast))
+ mark_nonreg_stores (PATTERN (insn), insn, fast);
+ else
+ mark_insn (insn, fast);
+ }
if (dump_file)
fprintf (dump_file, "Finished finding needed instructions:\n");
}
}
+
/* Mark every instruction that defines a register value that INSN uses. */
static void
struct df_link *defs;
struct df_ref **use_rec;
- /* If this is part of a libcall, mark the entire libcall. */
- if (find_reg_note (insn, REG_LIBCALL_ID, NULL_RTX))
- mark_libcall (insn, false);
-
for (use_rec = DF_INSN_USES (insn); *use_rec; use_rec++)
{
struct df_ref *use = *use_rec;
}
+/* Initialize global variables for a new DCE pass. */
+
static void
-end_ud_dce (void)
+init_dce (bool fast)
+{
+ if (!df_in_progress)
+ {
+ if (!fast)
+ df_chain_add_problem (DF_UD_CHAIN);
+ df_analyze ();
+ }
+
+ if (dump_file)
+ df_dump (dump_file);
+
+ if (fast)
+ {
+ bitmap_obstack_initialize (&dce_blocks_bitmap_obstack);
+ bitmap_obstack_initialize (&dce_tmp_bitmap_obstack);
+ }
+
+ marked = sbitmap_alloc (get_max_uid () + 1);
+ sbitmap_zero (marked);
+}
+
+
+/* Free the data allocated by init_dce. */
+
+static void
+fini_dce (bool fast)
{
sbitmap_free (marked);
- gcc_assert (VEC_empty (rtx, worklist));
+
+ if (fast)
+ {
+ bitmap_obstack_release (&dce_blocks_bitmap_obstack);
+ bitmap_obstack_release (&dce_tmp_bitmap_obstack);
+ }
}
{
rtx insn;
- df_in_progress = false;
init_dce (false);
prescan_insns_for_dce (false);
insn = VEC_pop (rtx, worklist);
mark_reg_dependencies (insn);
}
+
/* Before any insns are deleted, we must remove the chains since
they are not bidirectional. */
df_remove_problem (df_chain);
delete_unmarked_insns ();
- end_ud_dce ();
+ fini_dce (false);
return 0;
}
static bool
gate_ud_dce (void)
{
- return optimize > 1 && flag_dce;
+ return optimize > 1 && flag_dce
+ && dbg_cnt (dce_ud);
}
struct tree_opt_pass pass_ud_rtl_dce =
0, /* properties_destroyed */
0, /* todo_flags_start */
TODO_dump_func |
- TODO_df_finish |
+ TODO_df_finish | TODO_verify_rtl_sharing |
TODO_ggc_collect, /* todo_flags_finish */
'w' /* letter */
};
+
/* -------------------------------------------------------------------------
Fast DCE functions
------------------------------------------------------------------------- */
-
-/* Free the data allocated by init_dce. */
-
-static void
-fini_dce (void)
-{
- sbitmap_free (marked);
- bitmap_obstack_release (&dce_blocks_bitmap_obstack);
- bitmap_obstack_release (&dce_tmp_bitmap_obstack);
- df_in_progress = false;
-}
-
-
-/* Process basic block BB. Return true if the live_in set has
- changed. */
+/* Process basic block BB. Return true if the live_in set has changed. */
static bool
dce_process_block (basic_block bb, bool redo_out)
{
bitmap local_live = BITMAP_ALLOC (&dce_tmp_bitmap_obstack);
+ bitmap au;
rtx insn;
bool block_changed;
struct df_ref **def_rec, **use_rec;
bitmap_set_bit (local_live, DF_REF_REGNO (use));
}
+ /* These regs are considered always live so if they end up dying
+ because of some def, we need to bring the back again.
+ Calling df_simulate_fixup_sets has the disadvantage of calling
+ bb_has_eh_pred once per insn, so we cache the information here. */
+ if (bb_has_eh_pred (bb))
+ au = df->eh_block_artificial_uses;
+ else
+ au = df->regular_block_artificial_uses;
+
FOR_BB_INSNS_REVERSE (bb, insn)
if (INSN_P (insn))
{
- /* If this is a recursive call, the libcall will have already
- been marked. */
- if (!marked_insn_p (insn))
- {
- bool needed = false;
-
- /* The insn is needed if there is someone who uses the output. */
- for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++)
- if (bitmap_bit_p (local_live, DF_REF_REGNO (*def_rec)))
- {
- needed = true;
- break;
- }
+ bool needed = false;
+
+ /* The insn is needed if there is someone who uses the output. */
+ for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++)
+ if (bitmap_bit_p (local_live, DF_REF_REGNO (*def_rec))
+ || bitmap_bit_p (au, DF_REF_REGNO (*def_rec)))
+ {
+ needed = true;
+ break;
+ }
- if (needed)
- {
- rtx note = find_reg_note (insn, REG_LIBCALL_ID, NULL_RTX);
-
- /* If we need to mark an insn in the middle of a
- libcall, we need to back up to mark the entire
- libcall. Given that libcalls are rare, rescanning
- the block should be a reasonable solution to trying
- to figure out how to back up. */
- if (note)
- {
- if (dump_file)
- fprintf (dump_file, "needed libcall %d\n", INSN_UID (insn));
- mark_libcall (insn, true);
- BITMAP_FREE (local_live);
- return dce_process_block (bb, false);
- }
- else
- mark_insn (insn, true);
- }
- }
+ if (needed)
+ mark_insn (insn, true);
/* No matter if the instruction is needed or not, we remove
any regno in the defs from the live set. */
&& (!(DF_REF_FLAGS (def) & (DF_REF_PARTIAL | DF_REF_CONDITIONAL))))
bitmap_clear_bit (local_live, DF_REF_REGNO (def));
}
+
#ifdef EH_USES
/* Process the uses that are live into an exception handler. */
for (use_rec = df_get_artificial_uses (bb_index); *use_rec; use_rec++)
return block_changed;
}
+
+/* Perform fast DCE once initialization is done. */
+
static void
fast_dce (void)
{
int *postorder = df_get_postorder (DF_BACKWARD);
int n_blocks = df_get_n_blocks (DF_BACKWARD);
- int i;
/* The set of blocks that have been seen on this iteration. */
bitmap processed = BITMAP_ALLOC (&dce_blocks_bitmap_obstack);
/* The set of blocks that need to have the out vectors reset because
bitmap redo_out = BITMAP_ALLOC (&dce_blocks_bitmap_obstack);
bitmap all_blocks = BITMAP_ALLOC (&dce_blocks_bitmap_obstack);
bool global_changed = true;
-
- int loop_count = 0;
+ int i;
prescan_insns_for_dce (true);
while (global_changed)
{
global_changed = false;
+
for (i = 0; i < n_blocks; i++)
{
int index = postorder[i];
if (old_flag & DF_LR_RUN_DCE)
df_set_flags (DF_LR_RUN_DCE);
+
prescan_insns_for_dce (true);
}
- loop_count++;
}
delete_unmarked_insns ();
}
-/* Callback for running pass_rtl_dce. */
+/* Fast DCE. */
static unsigned int
rest_of_handle_fast_dce (void)
{
init_dce (true);
fast_dce ();
- fini_dce ();
- df_in_progress = false;
+ fini_dce (true);
return 0;
}
info, and then returns to allow the rest of the problems to be run.
This can be called by elsewhere but it will not update the bit
- vectors for any other problems than LR.
-*/
+ vectors for any other problems than LR. */
void
run_fast_df_dce (void)
df_in_progress = true;
rest_of_handle_fast_dce ();
+ df_in_progress = false;
+
df_set_flags (old_flags);
}
}
-static bool
-gate_fast_dce (void)
-{
- return optimize > 0 && flag_dce;
-}
+/* Run a fast DCE pass. */
-/* Run a fast DCE pass and return true if any instructions were
- deleted. */
-
-bool
+void
run_fast_dce (void)
{
- return gate_fast_dce () && (rest_of_handle_fast_dce (), something_changed);
+ if (flag_dce)
+ rest_of_handle_fast_dce ();
}
+static bool
+gate_fast_dce (void)
+{
+ return optimize > 0 && flag_dce
+ && dbg_cnt (dce_fast);
+}
+
struct tree_opt_pass pass_fast_rtl_dce =
{
"dce", /* name */
0, /* properties_destroyed */
0, /* todo_flags_start */
TODO_dump_func |
- TODO_df_finish |
+ TODO_df_finish | TODO_verify_rtl_sharing |
TODO_ggc_collect, /* todo_flags_finish */
'w' /* letter */
};
-
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