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Commit 9cdcebf9 by Bin Cheng Committed by Bin Cheng
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tree-predcom.c: Add general comment on Store-Store chains. 

	* tree-predcom.c: Add general comment on Store-Store chains.
	(split_data_refs_to_components): Postpone clearing eliminate_store_p
	flag in component.
	(get_chain_last_ref_at): Rename into...
	(get_chain_last_write_at): ...this.
	(get_chain_last_write_before_load): New function.
	(add_ref_to_chain): Promote type of chain from CT_STORE_LOAD to
	CT_STORE_STORE when write reference is added.
	(determine_roots_comp): Support load ref in CT_STORE_STORE chains.
	(is_inv_store_elimination_chain): Update get_chain_last_write_at call.
	(initialize_root_vars_store_elim_1): Ditto.
	(initialize_root_vars_store_elim_2): Ditto.  Replace rhs once default
	definition is created.
	(execute_pred_commoning_chain): Support load ref in CT_STORE_STORE
	chain by replacing it with dominant stored value.

	gcc/testsuite
	* gcc.dg/tree-ssa/predcom-dse-12.c: New test.

From-SVN: r254956
parent 90ef5773
Showing with 177 additions and 23 deletions
gcc/ChangeLog
2017-11-20 Bin Cheng <bin.cheng@arm.com>
* tree-predcom.c: Add general comment on Store-Store chains.
(split_data_refs_to_components): Postpone clearing eliminate_store_p
flag in component.
(get_chain_last_ref_at): Rename into...
(get_chain_last_write_at): ...this.
(get_chain_last_write_before_load): New function.
(add_ref_to_chain): Promote type of chain from CT_STORE_LOAD to
CT_STORE_STORE when write reference is added.
(determine_roots_comp): Support load ref in CT_STORE_STORE chains.
(is_inv_store_elimination_chain): Update get_chain_last_write_at call.
(initialize_root_vars_store_elim_1): Ditto.
(initialize_root_vars_store_elim_2): Ditto. Replace rhs once default
definition is created.
(execute_pred_commoning_chain): Support load ref in CT_STORE_STORE
chain by replacing it with dominant stored value.
2017-11-20 Bin Cheng <bin.cheng@arm.com>
* tree-predcom.c (add_ref_to_chain): Remove check on distance.
2017-11-20 Marc Glisse <marc.glisse@inria.fr>
gcc/testsuite/ChangeLog
2017-11-20 Bin Cheng <bin.cheng@arm.com>
* gcc.dg/tree-ssa/predcom-dse-12.c: New test.
2017-11-20 Marc Glisse <marc.glisse@inria.fr>
PR testsuite/82951
......
gcc/testsuite/gcc.dg/tree-ssa/predcom-dse-12.c 0 → 100644
/* { dg-do run } */
/* { dg-options "-O2 -fno-inline -fpredictive-commoning -fdump-tree-pcom-details" } */
int arr[105] = {2, 3, 5, 7, 11};
int result0[10] = {2, 3, 5, 7, 11};
int result1[10] = {0, -1, 5, -2, 11, 0};
int result2[10] = {0, 0, -1, -2, -2, 0};
int result3[10] = {0, 0, 0, -1, -2, -2, 0};
int result4[10] = {0, 0, 0, 0, -1, -2, -2, 0};
int result100[105] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -1, -2, -2, 0};
extern void abort (void);
int sum;
void __attribute__((noinline)) foo (int * restrict a, int len, int t1, int t2)
{
int i;
for (i = 0; i < len; i++)
{
a[i] = t1;
a[i + 3] = t2;
a[i + 1] = -1;
sum = sum + a[i] + a[i + 3];
}
}
void check (int *a, int *res, int len, int sval)
{
int i;
if (sum != sval)
abort ();
for (i = 0; i < len; i++)
if (a[i] != res[i])
abort ();
}
int main (void)
{
foo (arr, 0, 0, -2);
check (arr, result0, 10, 0);
foo (arr, 1, 0, -2);
check (arr, result1, 10, -2);
foo (arr, 2, 0, -2);
check (arr, result2, 10, -6);
foo (arr, 3, 0, -2);
check (arr, result3, 10, -12);
foo (arr, 4, 0, -2);
check (arr, result4, 10, -20);
foo (arr, 100, 0, -2);
check (arr, result100, 105, -220);
return 0;
}
/* { dg-final { scan-tree-dump "Store-stores chain" "pcom"} } */
gcc/tree-predcom.c
......@@ -192,6 +192,10 @@ along with GCC; see the file COPYING3. If not see
The interesting part is this can be viewed either as general store motion
or general dead store elimination in either intra/inter-iterations way.
With trivial effort, we also support load inside Store-Store chains if the
load is dominated by a store statement in the same iteration of loop. You
can see this as a restricted Store-Mixed-Load-Store chain.
TODO: For now, we don't support store-store chains in multi-exit loops. We
force to not unroll in case of store-store chain even if other chains might
ask for unroll.
......@@ -902,8 +906,6 @@ split_data_refs_to_components (struct loop *loop,
gimple_bb (dataref->stmt));
dataref->pos = comp->refs.length ();
comp->refs.quick_push (dataref);
if (DR_IS_READ (dr))
comp->eliminate_store_p = false;
}
for (i = 0; i < n; i++)
......@@ -1039,19 +1041,36 @@ get_chain_root (chain_p chain)
return chain->refs[0];
}
/* Given CHAIN, returns the last ref at DISTANCE, or NULL if it doesn't
/* Given CHAIN, returns the last write ref at DISTANCE, or NULL if it doesn't
exist. */
static inline dref
get_chain_last_ref_at (chain_p chain, unsigned distance)
get_chain_last_write_at (chain_p chain, unsigned distance)
{
unsigned i;
for (unsigned i = chain->refs.length (); i > 0; i--)
if (DR_IS_WRITE (chain->refs[i - 1]->ref)
&& distance == chain->refs[i - 1]->distance)
return chain->refs[i - 1];
for (i = chain->refs.length (); i > 0; i--)
if (distance == chain->refs[i - 1]->distance)
break;
return NULL;
}
/* Given CHAIN, returns the last write ref with the same distance before load
at index LOAD_IDX, or NULL if it doesn't exist. */
static inline dref
get_chain_last_write_before_load (chain_p chain, unsigned load_idx)
{
gcc_assert (load_idx < chain->refs.length ());
return (i > 0) ? chain->refs[i - 1] : NULL;
unsigned distance = chain->refs[load_idx]->distance;
for (unsigned i = load_idx; i > 0; i--)
if (DR_IS_WRITE (chain->refs[i - 1]->ref)
&& distance == chain->refs[i - 1]->distance)
return chain->refs[i - 1];
return NULL;
}
/* Adds REF to the chain CHAIN. */
......@@ -1075,6 +1094,10 @@ add_ref_to_chain (chain_p chain, dref ref)
chain->has_max_use_after = false;
}
/* Promote this chain to CT_STORE_STORE if it has multiple stores. */
if (DR_IS_WRITE (ref->ref))
chain->type = CT_STORE_STORE;
/* Don't set the flag for store-store chain since there is no use. */
if (chain->type != CT_STORE_STORE
&& ref->distance == chain->length
......@@ -1347,9 +1370,29 @@ determine_roots_comp (struct loop *loop,
}
comp->refs.qsort (order_drefs);
/* For Store-Store chain, we only support load if it is dominated by a
store statement in the same iteration of loop. */
if (comp->eliminate_store_p)
for (a = NULL, i = 0; i < comp->refs.length (); i++)
{
if (DR_IS_WRITE (comp->refs[i]->ref))
a = comp->refs[i];
else if (a == NULL || a->offset != comp->refs[i]->offset)
{
/* If there is load that is not dominated by a store in the
same iteration of loop, clear the flag so no Store-Store
chain is generated for this component. */
comp->eliminate_store_p = false;
break;
}
}
/* Determine roots and create chains for components. */
FOR_EACH_VEC_ELT (comp->refs, i, a)
{
if (!chain
|| (chain->type == CT_LOAD && DR_IS_WRITE (a->ref))
|| (!comp->eliminate_store_p && DR_IS_WRITE (a->ref))
|| wi::leu_p (MAX_DISTANCE, a->offset - last_ofs))
{
......@@ -1361,11 +1404,11 @@ determine_roots_comp (struct loop *loop,
else
release_chain (chain);
if (DR_IS_READ (a->ref))
type = CT_LOAD;
else
type = comp->eliminate_store_p ? CT_STORE_STORE : CT_STORE_LOAD;
/* Determine type of the chain. If the root reference is a load,
this can only be a CT_LOAD chain; other chains are intialized
to CT_STORE_LOAD and might be promoted to CT_STORE_STORE when
new reference is added. */
type = DR_IS_READ (a->ref) ? CT_LOAD : CT_STORE_LOAD;
chain = make_rooted_chain (a, type);
last_ofs = a->offset;
continue;
......@@ -1676,7 +1719,7 @@ is_inv_store_elimination_chain (struct loop *loop, chain_p chain)
values. */
for (unsigned i = 0; i < chain->length; i++)
{
dref a = get_chain_last_ref_at (chain, i);
dref a = get_chain_last_write_at (chain, i);
if (a == NULL)
continue;
......@@ -1720,7 +1763,7 @@ initialize_root_vars_store_elim_1 (chain_p chain)
/* Initialize root value for eliminated stores at each distance. */
for (i = 0; i < n; i++)
{
dref a = get_chain_last_ref_at (chain, i);
dref a = get_chain_last_write_at (chain, i);
if (a == NULL)
continue;
......@@ -1783,10 +1826,13 @@ initialize_root_vars_store_elim_2 (struct loop *loop,
{
/* Root value is rhs operand of the store to be eliminated if
it isn't loaded from memory before loop. */
dref a = get_chain_last_ref_at (chain, i);
dref a = get_chain_last_write_at (chain, i);
val = gimple_assign_rhs1 (a->stmt);
if (TREE_CLOBBER_P (val))
val = get_or_create_ssa_default_def (cfun, SSA_NAME_VAR (var));
{
val = get_or_create_ssa_default_def (cfun, SSA_NAME_VAR (var));
gimple_assign_set_rhs1 (a->stmt, val);
}
vtemps[n - i - 1] = val;
}
......@@ -2054,7 +2100,7 @@ static void
execute_pred_commoning_chain (struct loop *loop, chain_p chain,
bitmap tmp_vars)
{
unsigned i, n;
unsigned i;
dref a;
tree var;
bool in_lhs;
......@@ -2091,10 +2137,29 @@ execute_pred_commoning_chain (struct loop *loop, chain_p chain,
finalize_eliminated_stores (loop, chain);
}
/* Eliminate the stores killed by following store. */
n = chain->refs.length ();
for (i = 0; i < n - 1; i++)
remove_stmt (chain->refs[i]->stmt);
bool last_store_p = true;
for (i = chain->refs.length (); i > 0; i--)
{
a = chain->refs[i - 1];
/* Preserve the last store of the chain. Eliminate other stores
which are killed by the last one. */
if (DR_IS_WRITE (a->ref))
{
if (last_store_p)
last_store_p = false;
else
remove_stmt (a->stmt);
continue;
}
/* Any load in Store-Store chain must be dominated by a previous
store, we replace the load reference with rhs of the store. */
dref b = get_chain_last_write_before_load (chain, i - 1);
gcc_assert (b != NULL);
var = gimple_assign_rhs1 (b->stmt);
replace_ref_with (a->stmt, var, false, false);
}
}
else
{
......
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