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));
}
}
-/* Return true if the entire libcall sequence starting at INSN is dead.
- NOTE is the REG_LIBCALL note attached to INSN.
-
- 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)
-{
- 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 (insn == last)
- return false;
- insn = NEXT_INSN (insn);
- }
-
- while (insn != NEXT_INSN (last))
- {
- if (INSN_P (insn) && marked_insn_p (insn))
- return false;
- insn = NEXT_INSN (insn);
- }
-
- return true;
-}
-
-
/* Delete all REG_EQUAL notes of the registers INSN writes, to prevent
bad dangling REG_EQUAL notes. */
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))
- {
- 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;
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);
- }
-
/* 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. */
}
-/* 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. */
-
-static rtx
-prescan_libcall_for_dce (rtx insn, rtx note, bool fast)
-{
- rtx last = XEXP (note, 0);
-
- /* 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))
- mark_nonreg_stores (PATTERN (insn), insn, fast);
- insn = NEXT_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))
- mark_nonreg_stores (PATTERN (insn), insn, fast);
- insn = NEXT_INSN (insn);
- }
-
- return insn;
-}
-
-
/* Go through the instructions and mark those whose necessity is not
dependent on inter-instruction information. Make sure all other
instructions are not marked. */
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))
+ if (deletable_insn_p (insn, fast))
mark_nonreg_stores (PATTERN (insn), insn, fast);
else
mark_insn (insn, fast);
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);
}
}
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);
}
}
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