The following fixes PR68892, the BB vectorizer now happily creates
a load of dead vector loads (we had a similar bug with loop
single-element interleaving support in the past). Fixed as a side-effect
of making the SLP load cost reflect reality.
Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
Richard.
2015-12-14 Richard Biener <rguent...@suse.de>
PR tree-optimization/68892
* tree-vect-slp.c (vect_analyze_slp_cost_1): Properly compute
cost for permuted loads.
* gcc.dg/vect/bb-slp-pr68892.c: New testcase.
Index: gcc/tree-vect-slp.c
===================================================================
*** gcc/tree-vect-slp.c (revision 231617)
--- gcc/tree-vect-slp.c (working copy)
*************** vect_analyze_slp_cost_1 (slp_instance in
*** 1405,1414 ****
{
unsigned i;
slp_tree child;
! gimple *stmt, *s;
stmt_vec_info stmt_info;
tree lhs;
- unsigned group_size = SLP_INSTANCE_GROUP_SIZE (instance);
/* Recurse down the SLP tree. */
FOR_EACH_VEC_ELT (SLP_TREE_CHILDREN (node), i, child)
--- 1405,1413 ----
{
unsigned i;
slp_tree child;
! gimple *stmt;
stmt_vec_info stmt_info;
tree lhs;
/* Recurse down the SLP tree. */
FOR_EACH_VEC_ELT (SLP_TREE_CHILDREN (node), i, child)
*************** vect_analyze_slp_cost_1 (slp_instance in
*** 1427,1470 ****
node, prologue_cost_vec, body_cost_vec);
else
{
- int i;
gcc_checking_assert (DR_IS_READ (STMT_VINFO_DATA_REF (stmt_info)));
- /* If the load is permuted then the alignment is determined by
- the first group element not by the first scalar stmt DR. */
if (SLP_TREE_LOAD_PERMUTATION (node).exists ())
{
stmt = GROUP_FIRST_ELEMENT (stmt_info);
stmt_info = vinfo_for_stmt (stmt);
}
vect_model_load_cost (stmt_info, ncopies_for_cost, false,
node, prologue_cost_vec, body_cost_vec);
- /* If the load is permuted record the cost for the permutation.
- ??? Loads from multiple chains are let through here only
- for a single special case involving complex numbers where
- in the end no permutation is necessary. */
- FOR_EACH_VEC_ELT (SLP_TREE_SCALAR_STMTS (node), i, s)
- if ((STMT_VINFO_GROUP_FIRST_ELEMENT (vinfo_for_stmt (s))
- == STMT_VINFO_GROUP_FIRST_ELEMENT (stmt_info))
- && vect_get_place_in_interleaving_chain
- (s, STMT_VINFO_GROUP_FIRST_ELEMENT (stmt_info)) != i)
- {
- record_stmt_cost (body_cost_vec, group_size, vec_perm,
- stmt_info, 0, vect_body);
- break;
- }
}
}
! else
{
record_stmt_cost (body_cost_vec, ncopies_for_cost, vector_stmt,
stmt_info, 0, vect_body);
! if (SLP_TREE_TWO_OPERATORS (node))
! {
! record_stmt_cost (body_cost_vec, ncopies_for_cost, vector_stmt,
! stmt_info, 0, vect_body);
! record_stmt_cost (body_cost_vec, ncopies_for_cost, vec_perm,
! stmt_info, 0, vect_body);
! }
}
/* Scan operands and account for prologue cost of constants/externals.
--- 1426,1464 ----
node, prologue_cost_vec, body_cost_vec);
else
{
gcc_checking_assert (DR_IS_READ (STMT_VINFO_DATA_REF (stmt_info)));
if (SLP_TREE_LOAD_PERMUTATION (node).exists ())
{
+ /* If the load is permuted then the alignment is determined by
+ the first group element not by the first scalar stmt DR. */
stmt = GROUP_FIRST_ELEMENT (stmt_info);
stmt_info = vinfo_for_stmt (stmt);
+ /* Record the cost for the permutation. */
+ record_stmt_cost (body_cost_vec, ncopies_for_cost, vec_perm,
+ stmt_info, 0, vect_body);
+ /* And adjust the number of loads performed. */
+ unsigned nunits
+ = TYPE_VECTOR_SUBPARTS (STMT_VINFO_VECTYPE (stmt_info));
+ ncopies_for_cost
+ = (GROUP_SIZE (stmt_info) - GROUP_GAP (stmt_info)
+ + nunits - 1) / nunits;
+ ncopies_for_cost *= SLP_INSTANCE_UNROLLING_FACTOR (instance);
}
+ /* Record the cost for the vector loads. */
vect_model_load_cost (stmt_info, ncopies_for_cost, false,
node, prologue_cost_vec, body_cost_vec);
}
+ return;
}
!
! record_stmt_cost (body_cost_vec, ncopies_for_cost, vector_stmt,
! stmt_info, 0, vect_body);
! if (SLP_TREE_TWO_OPERATORS (node))
{
record_stmt_cost (body_cost_vec, ncopies_for_cost, vector_stmt,
stmt_info, 0, vect_body);
! record_stmt_cost (body_cost_vec, ncopies_for_cost, vec_perm,
! stmt_info, 0, vect_body);
}
/* Scan operands and account for prologue cost of constants/externals.
Index: gcc/testsuite/gcc.dg/vect/bb-slp-pr68892.c
===================================================================
*** gcc/testsuite/gcc.dg/vect/bb-slp-pr68892.c (revision 0)
--- gcc/testsuite/gcc.dg/vect/bb-slp-pr68892.c (revision 0)
***************
*** 0 ****
--- 1,16 ----
+ /* { dg-do compile } */
+ /* { dg-additional-options "-fvect-cost-model=dynamic" } */
+
+ double a[128][128];
+ double b[128];
+
+ void foo(void)
+ {
+ b[0] = a[0][0];
+ b[1] = a[1][0];
+ b[2] = a[2][0];
+ b[3] = a[3][0];
+ }
+
+ /* { dg-final { scan-tree-dump "not profitable" "slp2" } } */
+ /* { dg-final { scan-tree-dump-times "Basic block will be vectorized" 0
"slp2" } } */
