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Re: [PR debug/47624] improve value tracking in non-VTA locations
- From: Alexandre Oliva <aoliva at redhat dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Sun, 22 Apr 2012 15:08:39 -0300
- Subject: Re: [PR debug/47624] improve value tracking in non-VTA locations
- References: <orvd0l6u7u.fsf@livre.localdomain> <ork4d1g9mb.fsf@livre.localdomain>
On Jun 4, 2011, Alexandre Oliva <aoliva@redhat.com> wrote:
> On Feb 15, 2011, Alexandre Oliva <aoliva@redhat.com> wrote:
>> VTA only tracks locations of gimple regs, while addressable variables
>> still use the old var tracking strategy. This means addressable
>> variables, during var-tracking, got locations that were not based on
>> VALUEs, which failed immediately in the presence of auto-inc addresses.
>> The locations also tended to degrade in other ways, when a register
>> holding an address happened to be overwritten at a later point.
>> This patch arranges for us to track addresses of these variables as
>> VALUEs, and to emit new locations for them when a location whose value
>> was used to compute its address changes, fixing the problem.
>> The patch was regstrapped on x86_64-linux-gnu and i686-linux-gnu. Ok to
>> install?
> Ping? Retested on both platforms, unchanged except for fixing the typo
> s/deug/debug/ in the ChangeLog entry, that Jakub caught.
> http://gcc.gnu.org/ml/gcc-patches/2011-02/msg00981.html
Ping? Here's an updated patch that uses some of the recently-added
infrastructure to notify dependent variables and values when their
dependencies change.
It didn't look reasonable to add a field to all variables parts, or even
to all variables, just to hold a chain of loc_deps. For one-part
variables, we reused cur_loc, but after some measurements I concluded it
was perfectly ok to leave some backlinks behind or dangling, checking
them on activation.
It's not even a significant waste of memory: compare-debug bootstraps on
x86_64- and i686-linux-gnu leave only 1 loc_exp_dep allocated in the
pool I created for NOT_ONEPART loc_exp_deps in 3447 of the 5172
functions that leave any loc_exp_deps dangling off dependent values, at
the end of var-tracking. Of all these 5172 functions, only 4 ever went
beyond the initial pool allocation of 64 loc_exp_deps, which is less
than 0.05%, with 98 as the highest count on the bootstraps. A 32
initial allocation would have been enough to cover 99.71% of the
functions that have backlinks left behind at the end of var-tracking
(thus released along with the pool), but since even 64 loc_exp_deps add
up to as little as 512 pointers (half a 4KB page), I decided to leave it
at that.
Regstrapped on x86_64- and i686-linux-gnu. This ought to fix
gcc.dg/guality/pr43077-1.c -O1 on powerpc (which is what the bug report
is about), but I only verified that by examining a cross compiler
output.
Ok to install?
for gcc/ChangeLog
from Alexandre Oliva <aoliva@redhat.com>
PR debug/47624
* var-tracking.c (loc_exp_dep_pool): New.
(vt_emit_notes): Create and release the pool.
(compute_bb_dataflow): Use value-based locations in MO_VAL_SET.
(emit_notes_in_bb): Likewise.
(loc_exp_dep_insert): Deal with NOT_ONEPART vars.
(notify_dependents_of_changed_value): Likewise.
(notify_dependents_of_resolved_value): Check that NOT_ONEPART
variables don't have a VAR_LOC_DEP_LST.
(emit_note_insn_var_location): Expand NOT_ONEPART locs that are
VALUEs or MEMs of VALUEs.
Index: gcc/var-tracking.c
===================================================================
--- gcc/var-tracking.c.orig 2012-04-13 12:54:10.000000000 -0300
+++ gcc/var-tracking.c 2012-04-18 03:47:48.000000000 -0300
@@ -474,6 +474,9 @@ static alloc_pool loc_chain_pool;
/* Alloc pool for struct shared_hash_def. */
static alloc_pool shared_hash_pool;
+/* Alloc pool for struct loc_exp_dep_s for NOT_ONEPART variables. */
+static alloc_pool loc_exp_dep_pool;
+
/* Changed variables, notes will be emitted for them. */
static htab_t changed_variables;
@@ -6284,29 +6287,41 @@ compute_bb_dataflow (basic_block bb)
{
rtx loc = mo->u.loc;
rtx val, vloc, uloc;
+ rtx dstv, srcv;
vloc = loc;
uloc = XEXP (vloc, 1);
val = XEXP (vloc, 0);
vloc = uloc;
+ if (GET_CODE (uloc) == SET)
+ {
+ dstv = SET_DEST (uloc);
+ srcv = SET_SRC (uloc);
+ }
+ else
+ {
+ dstv = uloc;
+ srcv = NULL;
+ }
+
if (GET_CODE (val) == CONCAT)
{
- vloc = XEXP (val, 1);
+ dstv = vloc = XEXP (val, 1);
val = XEXP (val, 0);
}
if (GET_CODE (vloc) == SET)
{
- rtx vsrc = SET_SRC (vloc);
+ srcv = SET_SRC (vloc);
- gcc_assert (val != vsrc);
+ gcc_assert (val != srcv);
gcc_assert (vloc == uloc || VAL_NEEDS_RESOLUTION (loc));
- vloc = SET_DEST (vloc);
+ dstv = vloc = SET_DEST (vloc);
if (VAL_NEEDS_RESOLUTION (loc))
- val_resolve (out, val, vsrc, insn);
+ val_resolve (out, val, srcv, insn);
}
else if (VAL_NEEDS_RESOLUTION (loc))
{
@@ -6322,45 +6337,53 @@ compute_bb_dataflow (basic_block bb)
if (REG_P (uloc))
var_reg_delete (out, uloc, true);
else if (MEM_P (uloc))
- var_mem_delete (out, uloc, true);
+ {
+ gcc_assert (MEM_P (dstv));
+ gcc_assert (MEM_ATTRS (dstv) == MEM_ATTRS (uloc));
+ var_mem_delete (out, dstv, true);
+ }
}
else
{
bool copied_p = VAL_EXPR_IS_COPIED (loc);
- rtx set_src = NULL;
+ rtx src = NULL, dst = uloc;
enum var_init_status status = VAR_INIT_STATUS_INITIALIZED;
if (GET_CODE (uloc) == SET)
{
- set_src = SET_SRC (uloc);
- uloc = SET_DEST (uloc);
+ src = SET_SRC (uloc);
+ dst = SET_DEST (uloc);
}
if (copied_p)
{
if (flag_var_tracking_uninit)
{
- status = find_src_status (in, set_src);
+ status = find_src_status (in, src);
if (status == VAR_INIT_STATUS_UNKNOWN)
- status = find_src_status (out, set_src);
+ status = find_src_status (out, src);
}
- set_src = find_src_set_src (in, set_src);
+ src = find_src_set_src (in, src);
}
- if (REG_P (uloc))
- var_reg_delete_and_set (out, uloc, !copied_p,
- status, set_src);
- else if (MEM_P (uloc))
- var_mem_delete_and_set (out, uloc, !copied_p,
- status, set_src);
+ if (REG_P (dst))
+ var_reg_delete_and_set (out, dst, !copied_p,
+ status, srcv);
+ else if (MEM_P (dst))
+ {
+ gcc_assert (MEM_P (dstv));
+ gcc_assert (MEM_ATTRS (dstv) == MEM_ATTRS (dst));
+ var_mem_delete_and_set (out, dstv, !copied_p,
+ status, srcv);
+ }
}
}
else if (REG_P (uloc))
var_regno_delete (out, REGNO (uloc));
- val_store (out, val, vloc, insn, true);
+ val_store (out, val, dstv, insn, true);
}
break;
@@ -7602,8 +7625,13 @@ loc_exp_insert_dep (variable var, rtx x,
if (VAR_LOC_DEP_LST (xvar) && VAR_LOC_DEP_LST (xvar)->dv == var->dv)
return;
- VEC_quick_push (loc_exp_dep, VAR_LOC_DEP_VEC (var), NULL);
- led = VEC_last (loc_exp_dep, VAR_LOC_DEP_VEC (var));
+ if (var->onepart == NOT_ONEPART)
+ led = (loc_exp_dep *) pool_alloc (loc_exp_dep_pool);
+ else
+ {
+ VEC_quick_push (loc_exp_dep, VAR_LOC_DEP_VEC (var), NULL);
+ led = VEC_last (loc_exp_dep, VAR_LOC_DEP_VEC (var));
+ }
led->dv = var->dv;
led->value = x;
@@ -7679,8 +7707,12 @@ notify_dependents_of_resolved_value (var
gcc_checking_assert (dv_changed_p (dv));
}
- else if (!dv_changed_p (dv))
- continue;
+ else
+ {
+ gcc_checking_assert (dv_onepart_p (dv) != NOT_ONEPART);
+ if (!dv_changed_p (dv))
+ continue;
+ }
var = (variable) htab_find_with_hash (vars, dv, dv_htab_hash (dv));
@@ -8135,11 +8167,23 @@ emit_note_insn_var_location (void **varp
else if (last_limit > VAR_PART_OFFSET (var, i))
continue;
offset = VAR_PART_OFFSET (var, i);
- if (!var->var_part[i].cur_loc)
+ loc2 = var->var_part[i].cur_loc;
+ if (loc2 && GET_CODE (loc2) == MEM
+ && GET_CODE (XEXP (loc2, 0)) == VALUE)
+ {
+ rtx depval = XEXP (loc2, 0);
+
+ loc2 = vt_expand_loc (loc2, vars);
+
+ if (loc2)
+ loc_exp_insert_dep (var, depval, vars);
+ }
+ if (!loc2)
{
complete = false;
continue;
}
+ gcc_checking_assert (GET_CODE (loc2) != VALUE);
for (lc = var->var_part[i].loc_chain; lc; lc = lc->next)
if (var->var_part[i].cur_loc == lc->loc)
{
@@ -8147,7 +8191,6 @@ emit_note_insn_var_location (void **varp
break;
}
gcc_assert (lc);
- loc2 = var->var_part[i].cur_loc;
}
offsets[n_var_parts] = offset;
@@ -8361,7 +8404,6 @@ notify_dependents_of_changed_value (rtx
while ((led = VAR_LOC_DEP_LST (var)))
{
decl_or_value ldv = led->dv;
- void **islot;
variable ivar;
/* Deactivate and remove the backlink, as it was âused upâ. It
@@ -8386,13 +8428,34 @@ notify_dependents_of_changed_value (rtx
VEC_safe_push (rtx, stack, *changed_values_stack, dv_as_rtx (ldv));
break;
- default:
- islot = htab_find_slot_with_hash (htab, ldv, dv_htab_hash (ldv),
- NO_INSERT);
- ivar = (variable) *islot;
+ case ONEPART_VDECL:
+ ivar = (variable) htab_find_with_hash (htab, ldv, dv_htab_hash (ldv));
gcc_checking_assert (!VAR_LOC_DEP_LST (ivar));
variable_was_changed (ivar, NULL);
break;
+
+ case NOT_ONEPART:
+ pool_free (loc_exp_dep_pool, led);
+ ivar = (variable) htab_find_with_hash (htab, ldv, dv_htab_hash (ldv));
+ if (ivar)
+ {
+ int i = ivar->n_var_parts;
+ while (i--)
+ {
+ rtx loc = ivar->var_part[i].cur_loc;
+
+ if (loc && GET_CODE (loc) == MEM
+ && XEXP (loc, 0) == val)
+ {
+ variable_was_changed (ivar, NULL);
+ break;
+ }
+ }
+ }
+ break;
+
+ default:
+ gcc_unreachable ();
}
}
}
@@ -8729,29 +8792,41 @@ emit_notes_in_bb (basic_block bb, datafl
{
rtx loc = mo->u.loc;
rtx val, vloc, uloc;
+ rtx dstv, srcv;
vloc = loc;
uloc = XEXP (vloc, 1);
val = XEXP (vloc, 0);
vloc = uloc;
+ if (GET_CODE (uloc) == SET)
+ {
+ dstv = SET_DEST (uloc);
+ srcv = SET_SRC (uloc);
+ }
+ else
+ {
+ dstv = uloc;
+ srcv = NULL;
+ }
+
if (GET_CODE (val) == CONCAT)
{
- vloc = XEXP (val, 1);
+ dstv = vloc = XEXP (val, 1);
val = XEXP (val, 0);
}
if (GET_CODE (vloc) == SET)
{
- rtx vsrc = SET_SRC (vloc);
+ srcv = SET_SRC (vloc);
- gcc_assert (val != vsrc);
+ gcc_assert (val != srcv);
gcc_assert (vloc == uloc || VAL_NEEDS_RESOLUTION (loc));
- vloc = SET_DEST (vloc);
+ dstv = vloc = SET_DEST (vloc);
if (VAL_NEEDS_RESOLUTION (loc))
- val_resolve (set, val, vsrc, insn);
+ val_resolve (set, val, srcv, insn);
}
else if (VAL_NEEDS_RESOLUTION (loc))
{
@@ -8767,39 +8842,47 @@ emit_notes_in_bb (basic_block bb, datafl
if (REG_P (uloc))
var_reg_delete (set, uloc, true);
else if (MEM_P (uloc))
- var_mem_delete (set, uloc, true);
+ {
+ gcc_assert (MEM_P (dstv));
+ gcc_assert (MEM_ATTRS (dstv) == MEM_ATTRS (uloc));
+ var_mem_delete (set, dstv, true);
+ }
}
else
{
bool copied_p = VAL_EXPR_IS_COPIED (loc);
- rtx set_src = NULL;
+ rtx src = NULL, dst = uloc;
enum var_init_status status = VAR_INIT_STATUS_INITIALIZED;
if (GET_CODE (uloc) == SET)
{
- set_src = SET_SRC (uloc);
- uloc = SET_DEST (uloc);
+ src = SET_SRC (uloc);
+ dst = SET_DEST (uloc);
}
if (copied_p)
{
- status = find_src_status (set, set_src);
+ status = find_src_status (set, src);
- set_src = find_src_set_src (set, set_src);
+ src = find_src_set_src (set, src);
}
- if (REG_P (uloc))
- var_reg_delete_and_set (set, uloc, !copied_p,
- status, set_src);
- else if (MEM_P (uloc))
- var_mem_delete_and_set (set, uloc, !copied_p,
- status, set_src);
+ if (REG_P (dst))
+ var_reg_delete_and_set (set, dst, !copied_p,
+ status, srcv);
+ else if (MEM_P (dst))
+ {
+ gcc_assert (MEM_P (dstv));
+ gcc_assert (MEM_ATTRS (dstv) == MEM_ATTRS (dst));
+ var_mem_delete_and_set (set, dstv, !copied_p,
+ status, srcv);
+ }
}
}
else if (REG_P (uloc))
var_regno_delete (set, REGNO (uloc));
- val_store (set, val, vloc, insn, true);
+ val_store (set, val, dstv, insn, true);
emit_notes_for_changes (next_insn, EMIT_NOTE_BEFORE_INSN,
set->vars);
@@ -8908,9 +8991,13 @@ vt_emit_notes (void)
emit_notes = true;
if (MAY_HAVE_DEBUG_INSNS)
- dropped_values = htab_create (cselib_get_next_uid () * 2,
- variable_htab_hash, variable_htab_eq,
- variable_htab_free);
+ {
+ dropped_values = htab_create (cselib_get_next_uid () * 2,
+ variable_htab_hash, variable_htab_eq,
+ variable_htab_free);
+ loc_exp_dep_pool = create_alloc_pool ("loc_exp_dep pool",
+ sizeof (loc_exp_dep), 64);
+ }
dataflow_set_init (&cur);
@@ -8935,7 +9022,11 @@ vt_emit_notes (void)
dataflow_set_destroy (&cur);
if (MAY_HAVE_DEBUG_INSNS)
- htab_delete (dropped_values);
+ {
+ free_alloc_pool (loc_exp_dep_pool);
+ loc_exp_dep_pool = NULL;
+ htab_delete (dropped_values);
+ }
emit_notes = false;
}
--
Alexandre Oliva, freedom fighter http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/ FSF Latin America board member
Free Software Evangelist Red Hat Brazil Compiler Engineer