[gcc r14-7272] Do not count unused scalar use when marking STMT_VINFO_LIVE_P [PR113091]
Feng Xue
fxue@gcc.gnu.org
Tue Jan 16 03:36:33 GMT 2024
https://gcc.gnu.org/g:57f611604e8bab67af6c0bcfe6ea88c001408412
commit r14-7272-g57f611604e8bab67af6c0bcfe6ea88c001408412
Author: Feng Xue <fxue@os.amperecomputing.com>
Date: Thu Dec 28 16:55:39 2023 +0800
Do not count unused scalar use when marking STMT_VINFO_LIVE_P [PR113091]
When pattern recognition is involved, a statement whose definition is
consumed in some pattern, may not be included in the final replacement
pattern statements, and would be skipped when building SLP graph.
* Original
char a_c = *(char *) a;
char b_c = *(char *) b;
unsigned short a_s = (unsigned short) a_c;
int a_i = (int) a_s;
int b_i = (int) b_c;
int r_i = a_i - b_i;
* After pattern replacement
a_s = (unsigned short) a_c;
a_i = (int) a_s;
patt_b_s = (unsigned short) b_c; // b_i = (int) b_c
patt_b_i = (int) patt_b_s; // b_i = (int) b_c
patt_r_s = widen_minus(a_c, b_c); // r_i = a_i - b_i
patt_r_i = (int) patt_r_s; // r_i = a_i - b_i
The definitions of a_i(original statement) and b_i(pattern statement)
are related to, but actually not part of widen_minus pattern.
Vectorizing the pattern does not cause these definition statements to
be marked as PURE_SLP. For this case, we need to recursively check
whether their uses are all absorbed into vectorized code. But there
is an exception that some use may participate in an vectorized
operation via an external SLP node containing that use as an element.
gcc/ChangeLog:
PR tree-optimization/113091
* tree-vect-slp.cc (vect_slp_has_scalar_use): New function.
(vect_bb_slp_mark_live_stmts): New parameter scalar_use_map, check
scalar use with new function.
(vect_bb_slp_mark_live_stmts): New function as entry to existing
overriden functions with same name.
(vect_slp_analyze_operations): Call new entry function to mark
live statements.
gcc/testsuite/ChangeLog:
* gcc.target/aarch64/bb-slp-pr113091.c: New test.
Diff:
---
gcc/testsuite/gcc.target/aarch64/bb-slp-pr113091.c | 22 +++
gcc/tree-vect-slp.cc | 207 +++++++++++++++++----
2 files changed, 190 insertions(+), 39 deletions(-)
diff --git a/gcc/testsuite/gcc.target/aarch64/bb-slp-pr113091.c b/gcc/testsuite/gcc.target/aarch64/bb-slp-pr113091.c
new file mode 100644
index 00000000000..ff822e90b4a
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/bb-slp-pr113091.c
@@ -0,0 +1,22 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-O3 -fdump-tree-slp-details -ftree-slp-vectorize" } */
+
+int test(unsigned array[8]);
+
+int foo(char *a, char *b)
+{
+ unsigned array[8];
+
+ array[0] = (a[0] - b[0]);
+ array[1] = (a[1] - b[1]);
+ array[2] = (a[2] - b[2]);
+ array[3] = (a[3] - b[3]);
+ array[4] = (a[4] - b[4]);
+ array[5] = (a[5] - b[5]);
+ array[6] = (a[6] - b[6]);
+ array[7] = (a[7] - b[7]);
+
+ return test(array);
+}
+
+/* { dg-final { scan-tree-dump-times "Basic block will be vectorized using SLP" 1 "slp2" } } */
diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
index b6cce55ce90..086377a9ac0 100644
--- a/gcc/tree-vect-slp.cc
+++ b/gcc/tree-vect-slp.cc
@@ -6418,6 +6418,102 @@ vect_slp_analyze_node_operations (vec_info *vinfo, slp_tree node,
return res;
}
+/* Given a definition DEF, analyze if it will have any live scalar use after
+ performing SLP vectorization whose information is represented by BB_VINFO,
+ and record result into hash map SCALAR_USE_MAP as cache for later fast
+ check. If recursion DEPTH exceeds a limit, stop analysis and make a
+ conservative assumption. Return 0 if no scalar use, 1 if there is, -1
+ means recursion is limited. */
+
+static int
+vec_slp_has_scalar_use (bb_vec_info bb_vinfo, tree def,
+ hash_map<tree, int> &scalar_use_map,
+ int depth = 0)
+{
+ const int depth_limit = 2;
+ imm_use_iterator use_iter;
+ gimple *use_stmt;
+
+ if (int *res = scalar_use_map.get (def))
+ return *res;
+
+ int scalar_use = 1;
+
+ FOR_EACH_IMM_USE_STMT (use_stmt, use_iter, def)
+ {
+ if (is_gimple_debug (use_stmt))
+ continue;
+
+ stmt_vec_info use_stmt_info = bb_vinfo->lookup_stmt (use_stmt);
+
+ if (!use_stmt_info)
+ break;
+
+ if (PURE_SLP_STMT (vect_stmt_to_vectorize (use_stmt_info)))
+ continue;
+
+ /* Do not step forward when encounter PHI statement, since it may
+ involve cyclic reference and cause infinite recursive invocation. */
+ if (gimple_code (use_stmt) == GIMPLE_PHI)
+ break;
+
+ /* When pattern recognition is involved, a statement whose definition is
+ consumed in some pattern, may not be included in the final replacement
+ pattern statements, so would be skipped when building SLP graph.
+
+ * Original
+ char a_c = *(char *) a;
+ char b_c = *(char *) b;
+ unsigned short a_s = (unsigned short) a_c;
+ int a_i = (int) a_s;
+ int b_i = (int) b_c;
+ int r_i = a_i - b_i;
+
+ * After pattern replacement
+ a_s = (unsigned short) a_c;
+ a_i = (int) a_s;
+
+ patt_b_s = (unsigned short) b_c; // b_i = (int) b_c
+ patt_b_i = (int) patt_b_s; // b_i = (int) b_c
+
+ patt_r_s = widen_minus(a_c, b_c); // r_i = a_i - b_i
+ patt_r_i = (int) patt_r_s; // r_i = a_i - b_i
+
+ The definitions of a_i(original statement) and b_i(pattern statement)
+ are related to, but actually not part of widen_minus pattern.
+ Vectorizing the pattern does not cause these definition statements to
+ be marked as PURE_SLP. For this case, we need to recursively check
+ whether their uses are all absorbed into vectorized code. But there
+ is an exception that some use may participate in an vectorized
+ operation via an external SLP node containing that use as an element.
+ The parameter "scalar_use_map" tags such kind of SSA as having scalar
+ use in advance. */
+ tree lhs = gimple_get_lhs (use_stmt);
+
+ if (!lhs || TREE_CODE (lhs) != SSA_NAME)
+ break;
+
+ if (depth_limit && depth >= depth_limit)
+ return -1;
+
+ if ((scalar_use = vec_slp_has_scalar_use (bb_vinfo, lhs, scalar_use_map,
+ depth + 1)))
+ break;
+ }
+
+ if (end_imm_use_stmt_p (&use_iter))
+ scalar_use = 0;
+
+ /* If recursion is limited, do not cache result for non-root defs. */
+ if (!depth || scalar_use >= 0)
+ {
+ bool added = scalar_use_map.put (def, scalar_use);
+ gcc_assert (!added);
+ }
+
+ return scalar_use;
+}
+
/* Mark lanes of NODE that are live outside of the basic-block vectorized
region and that can be vectorized using vectorizable_live_operation
with STMT_VINFO_LIVE_P. Not handled live operations will cause the
@@ -6427,6 +6523,7 @@ static void
vect_bb_slp_mark_live_stmts (bb_vec_info bb_vinfo, slp_tree node,
slp_instance instance,
stmt_vector_for_cost *cost_vec,
+ hash_map<tree, int> &scalar_use_map,
hash_set<stmt_vec_info> &svisited,
hash_set<slp_tree> &visited)
{
@@ -6451,32 +6548,22 @@ vect_bb_slp_mark_live_stmts (bb_vec_info bb_vinfo, slp_tree node,
def_operand_p def_p;
FOR_EACH_PHI_OR_STMT_DEF (def_p, orig_stmt, op_iter, SSA_OP_DEF)
{
- imm_use_iterator use_iter;
- gimple *use_stmt;
- stmt_vec_info use_stmt_info;
- FOR_EACH_IMM_USE_STMT (use_stmt, use_iter, DEF_FROM_PTR (def_p))
- if (!is_gimple_debug (use_stmt))
- {
- use_stmt_info = bb_vinfo->lookup_stmt (use_stmt);
- if (!use_stmt_info
- || !PURE_SLP_STMT (vect_stmt_to_vectorize (use_stmt_info)))
- {
- STMT_VINFO_LIVE_P (stmt_info) = true;
- if (vectorizable_live_operation (bb_vinfo, stmt_info,
- node, instance, i,
- false, cost_vec))
- /* ??? So we know we can vectorize the live stmt
- from one SLP node. If we cannot do so from all
- or none consistently we'd have to record which
- SLP node (and lane) we want to use for the live
- operation. So make sure we can code-generate
- from all nodes. */
- mark_visited = false;
- else
- STMT_VINFO_LIVE_P (stmt_info) = false;
- break;
- }
- }
+ if (vec_slp_has_scalar_use (bb_vinfo, DEF_FROM_PTR (def_p),
+ scalar_use_map))
+ {
+ STMT_VINFO_LIVE_P (stmt_info) = true;
+ if (vectorizable_live_operation (bb_vinfo, stmt_info, node,
+ instance, i, false, cost_vec))
+ /* ??? So we know we can vectorize the live stmt from one SLP
+ node. If we cannot do so from all or none consistently
+ we'd have to record which SLP node (and lane) we want to
+ use for the live operation. So make sure we can
+ code-generate from all nodes. */
+ mark_visited = false;
+ else
+ STMT_VINFO_LIVE_P (stmt_info) = false;
+ }
+
/* We have to verify whether we can insert the lane extract
before all uses. The following is a conservative approximation.
We cannot put this into vectorizable_live_operation because
@@ -6495,6 +6582,10 @@ vect_bb_slp_mark_live_stmts (bb_vec_info bb_vinfo, slp_tree node,
from the latest stmt in a node. So we compensate for this
during code-generation, simply not replacing uses for those
hopefully rare cases. */
+ imm_use_iterator use_iter;
+ gimple *use_stmt;
+ stmt_vec_info use_stmt_info;
+
if (STMT_VINFO_LIVE_P (stmt_info))
FOR_EACH_IMM_USE_STMT (use_stmt, use_iter, DEF_FROM_PTR (def_p))
if (!is_gimple_debug (use_stmt)
@@ -6517,8 +6608,56 @@ vect_bb_slp_mark_live_stmts (bb_vec_info bb_vinfo, slp_tree node,
slp_tree child;
FOR_EACH_VEC_ELT (SLP_TREE_CHILDREN (node), i, child)
if (child && SLP_TREE_DEF_TYPE (child) == vect_internal_def)
- vect_bb_slp_mark_live_stmts (bb_vinfo, child, instance,
- cost_vec, svisited, visited);
+ vect_bb_slp_mark_live_stmts (bb_vinfo, child, instance, cost_vec,
+ scalar_use_map, svisited, visited);
+}
+
+/* Traverse all slp instances of BB_VINFO, and mark lanes of every node that
+ are live outside of the basic-block vectorized region and that can be
+ vectorized using vectorizable_live_operation with STMT_VINFO_LIVE_P. */
+
+static void
+vect_bb_slp_mark_live_stmts (bb_vec_info bb_vinfo)
+{
+ if (bb_vinfo->slp_instances.is_empty ())
+ return;
+
+ hash_set<stmt_vec_info> svisited;
+ hash_set<slp_tree> visited;
+ hash_map<tree, int> scalar_use_map;
+ auto_vec<slp_tree> worklist;
+
+ for (slp_instance instance : bb_vinfo->slp_instances)
+ if (!visited.add (SLP_INSTANCE_TREE (instance)))
+ worklist.safe_push (SLP_INSTANCE_TREE (instance));
+
+ do
+ {
+ slp_tree node = worklist.pop ();
+
+ if (SLP_TREE_DEF_TYPE (node) == vect_external_def)
+ {
+ for (tree op : SLP_TREE_SCALAR_OPS (node))
+ if (TREE_CODE (op) == SSA_NAME)
+ scalar_use_map.put (op, 1);
+ }
+ else
+ {
+ for (slp_tree child : SLP_TREE_CHILDREN (node))
+ if (child && !visited.add (child))
+ worklist.safe_push (child);
+ }
+ } while (!worklist.is_empty ());
+
+ visited.empty ();
+
+ for (slp_instance instance : bb_vinfo->slp_instances)
+ {
+ vect_location = instance->location ();
+ vect_bb_slp_mark_live_stmts (bb_vinfo, SLP_INSTANCE_TREE (instance),
+ instance, &instance->cost_vec,
+ scalar_use_map, svisited, visited);
+ }
}
/* Determine whether we can vectorize the reduction epilogue for INSTANCE. */
@@ -6684,17 +6823,7 @@ vect_slp_analyze_operations (vec_info *vinfo)
/* Compute vectorizable live stmts. */
if (bb_vec_info bb_vinfo = dyn_cast <bb_vec_info> (vinfo))
- {
- hash_set<stmt_vec_info> svisited;
- hash_set<slp_tree> visited;
- for (i = 0; vinfo->slp_instances.iterate (i, &instance); ++i)
- {
- vect_location = instance->location ();
- vect_bb_slp_mark_live_stmts (bb_vinfo, SLP_INSTANCE_TREE (instance),
- instance, &instance->cost_vec, svisited,
- visited);
- }
- }
+ vect_bb_slp_mark_live_stmts (bb_vinfo);
return !vinfo->slp_instances.is_empty ();
}
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