/* RTL dead code elimination.
- Copyright (C) 2005, 2006, 2007 Free Software Foundation, Inc.
+ Copyright (C) 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
This file is part of GCC.
#include "regs.h"
#include "hard-reg-set.h"
#include "flags.h"
+#include "except.h"
#include "df.h"
#include "cselib.h"
#include "dce.h"
#include "timevar.h"
#include "tree-pass.h"
#include "dbgcnt.h"
-
-DEF_VEC_I(int);
-DEF_VEC_ALLOC_I(int,heap);
+#include "tm_p.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;
+static bool find_call_stack_args (rtx, bool, bool, bitmap);
/* 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_refs_p (body))
- return false;
-
- if (flag_non_call_exceptions && may_trap_p (body))
- return false;
-
- return true;
+ return !volatile_refs_p (body);
}
}
+
/* Return true if INSN is a normal instruction that can be deleted by
the DCE pass. */
static bool
-deletable_insn_p (rtx insn, bool fast)
+deletable_insn_p (rtx insn, bool fast, bitmap arg_stores)
{
rtx body, x;
int i;
+ /* Don't delete jumps, notes and the like. */
if (!NONJUMP_INSN_P (insn))
return false;
+ /* Don't delete insns that can throw. */
+ if (!insn_nothrow_p (insn))
+ return false;
+
+ if (CALL_P (insn)
+ /* We cannot delete calls inside of the recursive dce because
+ this may cause basic blocks to be deleted and this messes up
+ the rest of the stack of optimization passes. */
+ && (!df_in_progress)
+ /* We cannot delete pure or const sibling calls because it is
+ hard to see the result. */
+ && (!SIBLING_CALL_P (insn))
+ /* We can delete dead const or pure calls as long as they do not
+ infinite loop. */
+ && (RTL_CONST_OR_PURE_CALL_P (insn)
+ && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn)))
+ return find_call_stack_args (insn, false, fast, arg_stores);
+
body = PATTERN (insn);
switch (GET_CODE (body))
{
case USE:
+ case VAR_LOCATION:
return false;
case CLOBBER:
}
-/* 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)
{
- if (insn)
- return TEST_BIT (marked, INSN_UID (insn));
- else
- /* Artificial defs are always needed and they do not have an
- insn. */
- return true;
+ /* Artificial defs are always needed and they do not have an insn.
+ We should never see them here. */
+ gcc_assert (insn);
+ return TEST_BIT (marked, INSN_UID (insn));
}
SET_BIT (marked, INSN_UID (insn));
if (dump_file)
fprintf (dump_file, " Adding insn %d to worklist\n", INSN_UID (insn));
+ if (CALL_P (insn)
+ && !df_in_progress
+ && !SIBLING_CALL_P (insn)
+ && (RTL_CONST_OR_PURE_CALL_P (insn)
+ && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn)))
+ find_call_stack_args (insn, true, fast, NULL);
}
}
}
-/* Initialize global variables for a new DCE pass. */
+/* Try to find all stack stores of CALL_INSN arguments if
+ ACCUMULATE_OUTGOING_ARGS. If all stack stores have been found
+ and it is therefore safe to eliminate the call, return true,
+ otherwise return false. This function should be first called
+ with DO_MARK false, and only when the CALL_INSN is actually
+ going to be marked called again with DO_MARK true. */
-static void
-init_dce (bool fast)
+static bool
+find_call_stack_args (rtx call_insn, bool do_mark, bool fast,
+ bitmap arg_stores)
{
- if (!df_in_progress)
+ rtx p, insn, prev_insn;
+ bool ret;
+ HOST_WIDE_INT min_sp_off, max_sp_off;
+ bitmap sp_bytes;
+
+ gcc_assert (CALL_P (call_insn));
+ if (!ACCUMULATE_OUTGOING_ARGS)
+ return true;
+
+ if (!do_mark)
{
- if (!fast)
- df_chain_add_problem (DF_UD_CHAIN);
- df_analyze ();
+ gcc_assert (arg_stores);
+ bitmap_clear (arg_stores);
}
- if (dump_file)
- df_dump (dump_file);
+ min_sp_off = INTTYPE_MAXIMUM (HOST_WIDE_INT);
+ max_sp_off = 0;
- bitmap_obstack_initialize (&dce_blocks_bitmap_obstack);
- bitmap_obstack_initialize (&dce_tmp_bitmap_obstack);
- marked = sbitmap_alloc (get_max_uid () + 1);
- sbitmap_zero (marked);
+ /* First determine the minimum and maximum offset from sp for
+ stored arguments. */
+ for (p = CALL_INSN_FUNCTION_USAGE (call_insn); p; p = XEXP (p, 1))
+ if (GET_CODE (XEXP (p, 0)) == USE
+ && MEM_P (XEXP (XEXP (p, 0), 0)))
+ {
+ rtx mem = XEXP (XEXP (p, 0), 0), addr, size;
+ HOST_WIDE_INT off = 0;
+ size = MEM_SIZE (mem);
+ if (size == NULL_RTX)
+ return false;
+ addr = XEXP (mem, 0);
+ if (GET_CODE (addr) == PLUS
+ && REG_P (XEXP (addr, 0))
+ && CONST_INT_P (XEXP (addr, 1)))
+ {
+ off = INTVAL (XEXP (addr, 1));
+ addr = XEXP (addr, 0);
+ }
+ if (addr != stack_pointer_rtx)
+ {
+ if (!REG_P (addr))
+ return false;
+ /* If not fast, use chains to see if addr wasn't set to
+ sp + offset. */
+ if (!fast)
+ {
+ df_ref *use_rec;
+ struct df_link *defs;
+ rtx set;
+
+ for (use_rec = DF_INSN_USES (call_insn); *use_rec; use_rec++)
+ if (rtx_equal_p (addr, DF_REF_REG (*use_rec)))
+ break;
+
+ if (*use_rec == NULL)
+ return false;
+
+ for (defs = DF_REF_CHAIN (*use_rec); defs; defs = defs->next)
+ if (! DF_REF_IS_ARTIFICIAL (defs->ref))
+ break;
+
+ if (defs == NULL)
+ return false;
+
+ set = single_set (DF_REF_INSN (defs->ref));
+ if (!set)
+ return false;
+
+ if (GET_CODE (SET_SRC (set)) != PLUS
+ || XEXP (SET_SRC (set), 0) != stack_pointer_rtx
+ || !CONST_INT_P (XEXP (SET_SRC (set), 1)))
+ return false;
+
+ off += INTVAL (XEXP (SET_SRC (set), 1));
+ }
+ else
+ return false;
+ }
+ min_sp_off = MIN (min_sp_off, off);
+ max_sp_off = MAX (max_sp_off, off + INTVAL (size));
+ }
+
+ if (min_sp_off >= max_sp_off)
+ return true;
+ sp_bytes = BITMAP_ALLOC (NULL);
+
+ /* Set bits in SP_BYTES bitmap for bytes relative to sp + min_sp_off
+ which contain arguments. Checking has been done in the previous
+ loop. */
+ for (p = CALL_INSN_FUNCTION_USAGE (call_insn); p; p = XEXP (p, 1))
+ if (GET_CODE (XEXP (p, 0)) == USE
+ && MEM_P (XEXP (XEXP (p, 0), 0)))
+ {
+ rtx mem = XEXP (XEXP (p, 0), 0), addr;
+ HOST_WIDE_INT off = 0, byte;
+ addr = XEXP (mem, 0);
+ if (GET_CODE (addr) == PLUS
+ && REG_P (XEXP (addr, 0))
+ && CONST_INT_P (XEXP (addr, 1)))
+ {
+ off = INTVAL (XEXP (addr, 1));
+ addr = XEXP (addr, 0);
+ }
+ if (addr != stack_pointer_rtx)
+ {
+ df_ref *use_rec;
+ struct df_link *defs;
+ rtx set;
+
+ for (use_rec = DF_INSN_USES (call_insn); *use_rec; use_rec++)
+ if (rtx_equal_p (addr, DF_REF_REG (*use_rec)))
+ break;
+
+ for (defs = DF_REF_CHAIN (*use_rec); defs; defs = defs->next)
+ if (! DF_REF_IS_ARTIFICIAL (defs->ref))
+ break;
+
+ set = single_set (DF_REF_INSN (defs->ref));
+ off += INTVAL (XEXP (SET_SRC (set), 1));
+ }
+ for (byte = off; byte < off + INTVAL (MEM_SIZE (mem)); byte++)
+ {
+ if (!bitmap_set_bit (sp_bytes, byte - min_sp_off))
+ gcc_unreachable ();
+ }
+ }
+
+ /* Walk backwards, looking for argument stores. The search stops
+ when seeing another call, sp adjustment or memory store other than
+ argument store. */
+ ret = false;
+ for (insn = PREV_INSN (call_insn); insn; insn = prev_insn)
+ {
+ rtx set, mem, addr;
+ HOST_WIDE_INT off, byte;
+
+ if (insn == BB_HEAD (BLOCK_FOR_INSN (call_insn)))
+ prev_insn = NULL_RTX;
+ else
+ prev_insn = PREV_INSN (insn);
+
+ if (CALL_P (insn))
+ break;
+
+ if (!INSN_P (insn))
+ continue;
+
+ set = single_set (insn);
+ if (!set || SET_DEST (set) == stack_pointer_rtx)
+ break;
+
+ if (!MEM_P (SET_DEST (set)))
+ continue;
+
+ mem = SET_DEST (set);
+ addr = XEXP (mem, 0);
+ off = 0;
+ if (GET_CODE (addr) == PLUS
+ && REG_P (XEXP (addr, 0))
+ && CONST_INT_P (XEXP (addr, 1)))
+ {
+ off = INTVAL (XEXP (addr, 1));
+ addr = XEXP (addr, 0);
+ }
+ if (addr != stack_pointer_rtx)
+ {
+ if (!REG_P (addr))
+ break;
+ if (!fast)
+ {
+ df_ref *use_rec;
+ struct df_link *defs;
+ rtx set;
+
+ for (use_rec = DF_INSN_USES (insn); *use_rec; use_rec++)
+ if (rtx_equal_p (addr, DF_REF_REG (*use_rec)))
+ break;
+
+ if (*use_rec == NULL)
+ break;
+
+ for (defs = DF_REF_CHAIN (*use_rec); defs; defs = defs->next)
+ if (! DF_REF_IS_ARTIFICIAL (defs->ref))
+ break;
+
+ if (defs == NULL)
+ break;
+
+ set = single_set (DF_REF_INSN (defs->ref));
+ if (!set)
+ break;
+
+ if (GET_CODE (SET_SRC (set)) != PLUS
+ || XEXP (SET_SRC (set), 0) != stack_pointer_rtx
+ || !CONST_INT_P (XEXP (SET_SRC (set), 1)))
+ break;
+
+ off += INTVAL (XEXP (SET_SRC (set), 1));
+ }
+ else
+ break;
+ }
+
+ if (GET_MODE_SIZE (GET_MODE (mem)) == 0)
+ break;
+
+ for (byte = off; byte < off + GET_MODE_SIZE (GET_MODE (mem)); byte++)
+ {
+ if (byte < min_sp_off
+ || byte >= max_sp_off
+ || !bitmap_clear_bit (sp_bytes, byte - min_sp_off))
+ break;
+ }
+
+ if (!deletable_insn_p (insn, fast, NULL))
+ break;
+
+ if (do_mark)
+ mark_insn (insn, fast);
+ else
+ bitmap_set_bit (arg_stores, INSN_UID (insn));
+
+ if (bitmap_empty_p (sp_bytes))
+ {
+ ret = true;
+ break;
+ }
+ }
+
+ BITMAP_FREE (sp_bytes);
+ if (!ret && arg_stores)
+ bitmap_clear (arg_stores);
+
+ return ret;
}
static void
delete_corresponding_reg_eq_notes (rtx insn)
{
- struct df_ref **def_rec;
+ df_ref *def_rec;
for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++)
{
- struct df_ref *def = *def_rec;
+ df_ref def = *def_rec;
unsigned int regno = DF_REF_REGNO (def);
/* This loop is a little tricky. We cannot just go down the
chain because it is being modified by the actions in the
anyway. */
while (DF_REG_EQ_USE_CHAIN (regno))
{
- struct df_ref *eq_use = DF_REG_EQ_USE_CHAIN (regno);
+ df_ref eq_use = DF_REG_EQ_USE_CHAIN (regno);
rtx noted_insn = DF_REF_INSN (eq_use);
rtx note = find_reg_note (noted_insn, REG_EQUAL, NULL_RTX);
if (!note)
}
-/* 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;
+ bool must_clean = false;
- something_changed = false;
- FOR_EACH_BB (bb)
- FOR_BB_INSNS_SAFE (bb, insn, next)
+ FOR_EACH_BB_REVERSE (bb)
+ FOR_BB_INSNS_REVERSE_SAFE (bb, insn, next)
if (INSN_P (insn))
{
+ /* Always delete no-op moves. */
if (noop_move_p (insn))
- {
- /* 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;
- }
- }
+ ;
+
+ /* 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. */
+ /* Beware that reaching a dbg counter limit here can result
+ in miscompiled file. This occurs when a group of insns
+ must be deleted together, typically because the kept insn
+ depends on the output from the deleted insn. Deleting
+ this insns in reverse order (both at the bb level and
+ when looking at the blocks) minimizes this, but does not
+ eliminate it, since it is possible for the using insn to
+ be top of a block and the producer to be at the bottom of
+ the block. However, in most cases this will only result
+ in an uninitialized use of an insn that is dead anyway.
+
+ However, there is one rare case that will cause a
+ miscompile: deletion of non-looping pure and constant
+ calls on a machine where ACCUMULATE_OUTGOING_ARGS is true.
+ In this case it is possible to remove the call, but leave
+ the argument pushes to the stack. Because of the changes
+ to the stack pointer, this will almost always lead to a
+ miscompile. */
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 a pure or const call is deleted, this may make the cfg
+ have unreachable blocks. We rememeber this and call
+ delete_unreachable_blocks at the end. */
+ if (CALL_P (insn))
+ must_clean = true;
+ /* 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;
-
- mark_insn (start_insn, delete_parm);
- insn = NEXT_INSN (start_insn);
-
- /* 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))
- {
- 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;
- }
- }
-
- for (insn = PREV_INSN (start_insn); insn; insn = PREV_INSN (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 backward libcall %d[%d]\n",
- INSN_UID (insn), id);
- }
- }
- else
- break;
- }
- }
+ /* Deleted a pure or const call. */
+ if (must_clean)
+ delete_unreachable_blocks ();
}
prescan_insns_for_dce (bool fast)
{
basic_block bb;
- rtx insn;
-
+ rtx insn, prev;
+ bitmap arg_stores = NULL;
+
if (dump_file)
fprintf (dump_file, "Finding needed instructions:\n");
-
+
+ if (!df_in_progress && ACCUMULATE_OUTGOING_ARGS)
+ arg_stores = BITMAP_ALLOC (NULL);
+
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_REVERSE_SAFE (bb, insn, prev)
+ if (INSN_P (insn))
+ {
+ /* Don't mark argument stores now. They will be marked
+ if needed when the associated CALL is marked. */
+ if (arg_stores && bitmap_bit_p (arg_stores, INSN_UID (insn)))
+ continue;
+ if (deletable_insn_p (insn, fast, arg_stores))
+ mark_nonreg_stores (PATTERN (insn), insn, fast);
+ else
+ mark_insn (insn, fast);
+ }
+ /* find_call_stack_args only looks at argument stores in the
+ same bb. */
+ if (arg_stores)
+ bitmap_clear (arg_stores);
+ }
+
+ if (arg_stores)
+ BITMAP_FREE (arg_stores);
if (dump_file)
fprintf (dump_file, "Finished finding needed instructions:\n");
{
basic_block bb;
struct df_link *defs;
- struct df_ref **use_rec;
+ df_ref *use_rec;
FOR_ALL_BB (bb)
{
- for (use_rec = df_get_artificial_uses (bb->index);
+ for (use_rec = df_get_artificial_uses (bb->index);
*use_rec; use_rec++)
for (defs = DF_REF_CHAIN (*use_rec); defs; defs = defs->next)
- mark_insn (DF_REF_INSN (defs->ref), false);
+ if (! DF_REF_IS_ARTIFICIAL (defs->ref))
+ mark_insn (DF_REF_INSN (defs->ref), false);
}
}
+
/* Mark every instruction that defines a register value that INSN uses. */
static void
mark_reg_dependencies (rtx insn)
{
struct df_link *defs;
- struct df_ref **use_rec;
+ 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);
+ if (DEBUG_INSN_P (insn))
+ return;
for (use_rec = DF_INSN_USES (insn); *use_rec; use_rec++)
{
- struct df_ref *use = *use_rec;
+ df_ref use = *use_rec;
if (dump_file)
{
fprintf (dump_file, "Processing use of ");
fprintf (dump_file, " in insn %d:\n", INSN_UID (insn));
}
for (defs = DF_REF_CHAIN (use); defs; defs = defs->next)
- mark_insn (DF_REF_INSN (defs->ref), false);
+ if (! DF_REF_IS_ARTIFICIAL (defs->ref))
+ mark_insn (DF_REF_INSN (defs->ref), false);
+ }
+}
+
+
+/* Initialize global variables for a new DCE pass. */
+
+static 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
-end_ud_dce (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);
}
+ VEC_free (rtx, heap, worklist);
+
/* 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 =
+struct rtl_opt_pass pass_ud_rtl_dce =
{
- "dce", /* name */
- gate_ud_dce, /* gate */
- rest_of_handle_ud_dce, /* execute */
+ {
+ RTL_PASS,
+ "ud dce", /* name */
+ gate_ud_dce, /* gate */
+ rest_of_handle_ud_dce, /* execute */
NULL, /* sub */
NULL, /* next */
0, /* static_pass_number */
0, /* todo_flags_start */
TODO_dump_func |
TODO_df_finish | TODO_verify_rtl_sharing |
- TODO_ggc_collect, /* todo_flags_finish */
- 'w' /* letter */
+ TODO_ggc_collect /* todo_flags_finish */
+ }
};
+
/* -------------------------------------------------------------------------
Fast DCE functions
------------------------------------------------------------------------- */
+/* Process basic block BB. Return true if the live_in set has
+ changed. REDO_OUT is true if the info at the bottom of the block
+ needs to be recalculated before starting. AU is the proper set of
+ artificial uses. */
-/* Free the data allocated by init_dce. */
-
-static void
-fini_dce (void)
+static bool
+byte_dce_process_block (basic_block bb, bool redo_out, bitmap au)
{
- sbitmap_free (marked);
- bitmap_obstack_release (&dce_blocks_bitmap_obstack);
- bitmap_obstack_release (&dce_tmp_bitmap_obstack);
- df_in_progress = false;
+ bitmap local_live = BITMAP_ALLOC (&dce_tmp_bitmap_obstack);
+ rtx insn;
+ bool block_changed;
+ df_ref *def_rec;
+
+ if (redo_out)
+ {
+ /* Need to redo the live_out set of this block if when one of
+ the succs of this block has had a change in it live in
+ set. */
+ edge e;
+ edge_iterator ei;
+ df_confluence_function_n con_fun_n = df_byte_lr->problem->con_fun_n;
+ bitmap_clear (DF_BYTE_LR_OUT (bb));
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ (*con_fun_n) (e);
+ }
+
+ if (dump_file)
+ {
+ fprintf (dump_file, "processing block %d live out = ", bb->index);
+ df_print_byte_regset (dump_file, DF_BYTE_LR_OUT (bb));
+ }
+
+ bitmap_copy (local_live, DF_BYTE_LR_OUT (bb));
+
+ df_byte_lr_simulate_artificial_refs_at_end (bb, local_live);
+
+ FOR_BB_INSNS_REVERSE (bb, insn)
+ if (INSN_P (insn))
+ {
+ /* The insn is needed if there is someone who uses the output. */
+ for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++)
+ {
+ df_ref def = *def_rec;
+ unsigned int last;
+ unsigned int dregno = DF_REF_REGNO (def);
+ unsigned int start = df_byte_lr_get_regno_start (dregno);
+ unsigned int len = df_byte_lr_get_regno_len (dregno);
+
+ unsigned int sb;
+ unsigned int lb;
+ /* This is one of the only places where DF_MM_MAY should
+ be used for defs. Need to make sure that we are
+ checking for all of the bits that may be used. */
+
+ if (!df_compute_accessed_bytes (def, DF_MM_MAY, &sb, &lb))
+ {
+ start += sb;
+ len = lb - sb;
+ }
+
+ if (bitmap_bit_p (au, dregno))
+ {
+ mark_insn (insn, true);
+ goto quickexit;
+ }
+
+ last = start + len;
+ while (start < last)
+ if (bitmap_bit_p (local_live, start++))
+ {
+ mark_insn (insn, true);
+ goto quickexit;
+ }
+ }
+
+ quickexit:
+
+ /* No matter if the instruction is needed or not, we remove
+ any regno in the defs from the live set. */
+ df_byte_lr_simulate_defs (insn, local_live);
+
+ /* On the other hand, we do not allow the dead uses to set
+ anything in local_live. */
+ if (marked_insn_p (insn))
+ df_byte_lr_simulate_uses (insn, local_live);
+
+ if (dump_file)
+ {
+ fprintf (dump_file, "finished processing insn %d live out = ",
+ INSN_UID (insn));
+ df_print_byte_regset (dump_file, local_live);
+ }
+ }
+
+ df_byte_lr_simulate_artificial_refs_at_top (bb, local_live);
+
+ block_changed = !bitmap_equal_p (local_live, DF_BYTE_LR_IN (bb));
+ if (block_changed)
+ bitmap_copy (DF_BYTE_LR_IN (bb), local_live);
+ BITMAP_FREE (local_live);
+ return block_changed;
}
/* Process basic block BB. Return true if the live_in set has
- changed. */
+ changed. REDO_OUT is true if the info at the bottom of the block
+ needs to be recalculated before starting. AU is the proper set of
+ artificial uses. */
static bool
-dce_process_block (basic_block bb, bool redo_out)
+dce_process_block (basic_block bb, bool redo_out, bitmap au)
{
bitmap local_live = BITMAP_ALLOC (&dce_tmp_bitmap_obstack);
- bitmap au;
rtx insn;
bool block_changed;
- struct df_ref **def_rec, **use_rec;
- unsigned int bb_index = bb->index;
+ df_ref *def_rec;
if (redo_out)
{
if (dump_file)
{
- fprintf (dump_file, "processing block %d live out = ", bb->index);
+ fprintf (dump_file, "processing block %d lr out = ", bb->index);
df_print_regset (dump_file, DF_LR_OUT (bb));
}
bitmap_copy (local_live, DF_LR_OUT (bb));
- /* Process the artificial defs and uses at the bottom of the block. */
- for (def_rec = df_get_artificial_defs (bb_index); *def_rec; def_rec++)
- {
- struct df_ref *def = *def_rec;
- if (((DF_REF_FLAGS (def) & DF_REF_AT_TOP) == 0)
- && (!(DF_REF_FLAGS (def) & (DF_REF_PARTIAL | DF_REF_CONDITIONAL))))
- bitmap_clear_bit (local_live, DF_REF_REGNO (def));
- }
-
- for (use_rec = df_get_artificial_uses (bb_index); *use_rec; use_rec++)
- {
- struct df_ref *use = *use_rec;
- if ((DF_REF_FLAGS (use) & DF_REF_AT_TOP) == 0)
- 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;
+ df_simulate_initialize_backwards (bb, local_live);
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))
- || 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);
- }
- }
-
+ 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)
+ 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_simulate_defs (insn, local_live);
if (marked_insn_p (insn))
df_simulate_uses (insn, local_live);
}
-
- for (def_rec = df_get_artificial_defs (bb_index); *def_rec; def_rec++)
- {
- struct df_ref *def = *def_rec;
- if ((DF_REF_FLAGS (def) & DF_REF_AT_TOP)
- && (!(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++)
- {
- /* Add use to set of uses in this BB. */
- struct df_ref *use = *use_rec;
- if (DF_REF_FLAGS (use) & DF_REF_AT_TOP)
- bitmap_set_bit (local_live, DF_REF_REGNO (use));
- }
-#endif
+
+ df_simulate_finalize_backwards (bb, local_live);
block_changed = !bitmap_equal_p (local_live, DF_LR_IN (bb));
if (block_changed)
return block_changed;
}
+
+/* Perform fast DCE once initialization is done. If BYTE_LEVEL is
+ true, use the byte level dce, otherwise do it at the pseudo
+ level. */
+
static void
-fast_dce (void)
+fast_dce (bool byte_level)
{
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 all_blocks = BITMAP_ALLOC (&dce_blocks_bitmap_obstack);
bool global_changed = true;
- int loop_count = 0;
+ /* 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. */
+ bitmap au = df->regular_block_artificial_uses;
+ bitmap au_eh = df->eh_block_artificial_uses;
+ int i;
prescan_insns_for_dce (true);
while (global_changed)
{
global_changed = false;
+
for (i = 0; i < n_blocks; i++)
{
int index = postorder[i];
continue;
}
- local_changed
- = dce_process_block (bb, bitmap_bit_p (redo_out, index));
+ if (byte_level)
+ local_changed
+ = byte_dce_process_block (bb, bitmap_bit_p (redo_out, index),
+ bb_has_eh_pred (bb) ? au_eh : au);
+ else
+ local_changed
+ = dce_process_block (bb, bitmap_bit_p (redo_out, index),
+ bb_has_eh_pred (bb) ? au_eh : au);
bitmap_set_bit (processed, index);
-
+
if (local_changed)
{
edge e;
bitmap_set_bit (redo_out, e->src->index);
}
}
-
+
if (global_changed)
{
/* Turn off the RUN_DCE flag to prevent recursive calls to
sbitmap_zero (marked);
bitmap_clear (processed);
bitmap_clear (redo_out);
-
+
/* We do not need to rescan any instructions. We only need
to redo the dataflow equations for the blocks that had a
change at the top of the block. Then we need to redo the
- iteration. */
- df_analyze_problem (df_lr, all_blocks, postorder, n_blocks);
+ iteration. */
+ if (byte_level)
+ df_analyze_problem (df_byte_lr, all_blocks, postorder, n_blocks);
+ else
+ df_analyze_problem (df_lr, all_blocks, postorder, n_blocks);
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 register level DCE. */
static unsigned int
rest_of_handle_fast_dce (void)
{
init_dce (true);
- fast_dce ();
- fini_dce ();
- df_in_progress = false;
+ fast_dce (false);
+ fini_dce (true);
+ return 0;
+}
+
+
+/* Fast byte level DCE. */
+
+static unsigned int
+rest_of_handle_fast_byte_dce (void)
+{
+ df_byte_lr_add_problem ();
+ init_dce (true);
+ fast_dce (true);
+ 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)
/* If dce is able to delete something, it has to happen
immediately. Otherwise there will be problems handling the
eq_notes. */
- enum df_changeable_flags old_flags
- = df_clear_flags (DF_DEFER_INSN_RESCAN + DF_NO_INSN_RESCAN);
-
+ int old_flags =
+ df_clear_flags (DF_DEFER_INSN_RESCAN + DF_NO_INSN_RESCAN);
+
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 and return true if any instructions were
- deleted. */
+/* Run a fast DCE pass. */
-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 ();
}
-struct tree_opt_pass pass_fast_rtl_dce =
+static bool
+gate_fast_dce (void)
+{
+ return optimize > 0 && flag_dce
+ && dbg_cnt (dce_fast);
+}
+
+struct rtl_opt_pass pass_fast_rtl_dce =
{
- "dce", /* name */
+ {
+ RTL_PASS,
+ "rtl dce", /* name */
gate_fast_dce, /* gate */
rest_of_handle_fast_dce, /* execute */
NULL, /* sub */
0, /* todo_flags_start */
TODO_dump_func |
TODO_df_finish | TODO_verify_rtl_sharing |
- TODO_ggc_collect, /* todo_flags_finish */
- 'w' /* letter */
+ TODO_ggc_collect /* todo_flags_finish */
+ }
};
+struct rtl_opt_pass pass_fast_rtl_byte_dce =
+{
+ {
+ RTL_PASS,
+ "byte-dce", /* name */
+ gate_fast_dce, /* gate */
+ rest_of_handle_fast_byte_dce, /* execute */
+ NULL, /* sub */
+ NULL, /* next */
+ 0, /* static_pass_number */
+ TV_DCE, /* tv_id */
+ 0, /* properties_required */
+ 0, /* properties_provided */
+ 0, /* properties_destroyed */
+ 0, /* todo_flags_start */
+ TODO_dump_func |
+ TODO_df_finish | TODO_verify_rtl_sharing |
+ TODO_ggc_collect /* todo_flags_finish */
+ }
+};
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