Hi!
This patch attempts to fix a regression caused by the
http://gcc.gnu.org/r208220 change.
In particular, because cselib_reset_table called immediately after
cselib_preserve_only_values removes VALUEs with zero locs and thus clears
n_useless_values, if we don't remove_useless_values right away (as was done
before the patch), we might not call discard_useless_locs at all).
The problem with that is var-tracking relies on preserved values not
referencing non-preserved values without any locs.
The patch ensures we discard_useless_locs at least sometimes during
vt_initialize (if the cumulative number of dropped and useless VALUEs goes
over certain amount) and ensures we do it at least once at the end of
vt_initialize.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2014-03-04 Jakub Jelinek <ja...@redhat.com>
PR middle-end/60381
* cselib.h (cselib_remove_useless_values): New prototype.
* var-tracking.c (vt_initialize): Call it at the end.
* cselib.c (n_dropped_useless_values): New counter.
(cselib_reset_table): Accumulate n_useless_values
into n_dropped_useless_values.
(remove_useless_values): Revert 2014-02-28 change.
Clear n_dropped_useless_values.
(cselib_preserve_only_values): Don't call remove_useless_values,
just do traversal with discard_useless_locs conditionally
on n_dropped_useless_values + n_useless_values being big enough.
(cselib_remove_useless_values): New function.
(cselib_process_insn): Revert 2014-02-28 change.
(cselib_finish): Clear n_dropped_useless_values.
--- gcc/cselib.h.jj 2014-01-03 11:40:57.000000000 +0100
+++ gcc/cselib.h 2014-03-03 19:23:48.633335911 +0100
@@ -95,6 +95,7 @@ extern unsigned int cselib_get_next_uid
extern void cselib_preserve_value (cselib_val *);
extern bool cselib_preserved_value_p (cselib_val *);
extern void cselib_preserve_only_values (void);
+extern void cselib_remove_useless_values (vec<rtx>);
extern void cselib_preserve_cfa_base_value (cselib_val *, unsigned int);
extern void cselib_add_permanent_equiv (cselib_val *, rtx, rtx);
extern bool cselib_have_permanent_equivalences (void);
--- gcc/var-tracking.c.jj 2014-03-03 18:28:18.000000000 +0100
+++ gcc/var-tracking.c 2014-03-03 19:27:07.518208397 +0100
@@ -10149,6 +10149,8 @@ vt_initialize (void)
}
}
+ if (MAY_HAVE_DEBUG_INSNS)
+ cselib_remove_useless_values (preserved_values);
hard_frame_pointer_adjustment = -1;
VTI (ENTRY_BLOCK_PTR_FOR_FN (cfun))->flooded = true;
cfa_base_rtx = NULL_RTX;
--- gcc/cselib.c.jj 2014-03-03 18:28:18.000000000 +0100
+++ gcc/cselib.c 2014-03-03 19:28:19.832782951 +0100
@@ -200,6 +200,7 @@ static unsigned int cselib_nregs;
values. */
static int n_useless_values;
static int n_useless_debug_values;
+static int n_dropped_useless_values;
/* Count values whose locs have been taken exclusively from debug
insns for the entire life of the value. */
@@ -546,7 +547,11 @@ cselib_reset_table (unsigned int num)
}
if (cselib_preserve_constants)
- cselib_hash_table.traverse <void *, preserve_constants_and_equivs> (NULL);
+ {
+ n_dropped_useless_values += n_useless_values;
+ cselib_hash_table.traverse <void *,
+ preserve_constants_and_equivs> (NULL);
+ }
else
{
cselib_hash_table.empty ();
@@ -681,14 +686,6 @@ remove_useless_values (void)
{
cselib_val **p, *v;
- if (n_useless_values <= MAX_USELESS_VALUES
- /* remove_useless_values is linear in the hash table size. Avoid
- quadratic behavior for very large hashtables with very few
- useless elements. */
- || ((unsigned int)n_useless_values
- <= (cselib_hash_table.elements () - n_debug_values) / 4))
- return;
-
/* First pass: eliminate locations that reference the value. That in
turn can make more values useless. */
do
@@ -712,6 +709,7 @@ remove_useless_values (void)
n_useless_values += n_useless_debug_values;
n_debug_values -= n_useless_debug_values;
n_useless_debug_values = 0;
+ n_dropped_useless_values = 0;
cselib_hash_table.traverse <void *, discard_useless_values> (NULL);
@@ -763,11 +761,43 @@ cselib_preserve_only_values (void)
cselib_invalidate_mem (callmem);
- remove_useless_values ();
+ if ((n_dropped_useless_values + n_useless_values) > MAX_USELESS_VALUES
+ /* Traversal with discard_useless_locs is linear in the hash table
+ size. Avoid quadratic behavior for very large hashtables with
+ very few useless elements. */
+ && ((unsigned int) (n_dropped_useless_values + n_useless_values)
+ > (cselib_hash_table.elements () - n_debug_values) / 4))
+ {
+ /* Eliminate locations that reference the value. That in
+ turn can make more values useless. */
+ do
+ {
+ values_became_useless = 0;
+ cselib_hash_table.traverse <void *, discard_useless_locs> (NULL);
+ }
+ while (values_became_useless);
+ n_dropped_useless_values = 0;
+ }
gcc_assert (first_containing_mem == &dummy_val);
}
+/* Clean out useless values (i.e. those which no longer have locations
+ associated with them) from both hash tables. */
+
+void
+cselib_remove_useless_values (vec<rtx> values)
+{
+ unsigned int i;
+ rtx val;
+
+ if (n_dropped_useless_values)
+ remove_useless_values ();
+ cselib_preserved_hash_table.traverse <void *, discard_useless_locs> (NULL);
+ FOR_EACH_VEC_ELT (values, i, val)
+ discard_useless_locs (&CSELIB_VAL_PTR (val), NULL);
+}
+
/* Arrange for a value to be marked as based on stack pointer
for find_base_term purposes. */
@@ -2720,7 +2750,13 @@ cselib_process_insn (rtx insn)
cselib_current_insn = NULL_RTX;
- remove_useless_values ();
+ if (n_useless_values > MAX_USELESS_VALUES
+ /* remove_useless_values is linear in the hash table size. Avoid
+ quadratic behavior for very large hashtables with very few
+ useless elements. */
+ && ((unsigned int)n_useless_values
+ > (cselib_hash_table.elements () - n_debug_values) / 4))
+ remove_useless_values ();
}
/* Initialize cselib for one pass. The caller must also call
@@ -2790,6 +2826,7 @@ cselib_finish (void)
n_useless_values = 0;
n_useless_debug_values = 0;
n_debug_values = 0;
+ n_dropped_useless_values = 0;
next_uid = 0;
}
Jakub
