Richard Biener <rguent...@suse.de> writes:
> The following adds a new --param for debugging the vectorizers alignment
> peeling by increasing the cost of aligned stores.
>
> Bootstrap & regtest running on x86_64-unknown-linux-gnu.
>
> This makes the PR115843 testcase fail again on trunk (but not on the
> branch), seemingly uncovering another backend issue. It makes the
> testcase get alignment peeling even with the zen4 costs fixed.
>
> Any objection?
Seems ok to me. Not sure I understand the mechanics of how this makes
the testcase get alignment peeling though. I'd assumed increasing the
cost of aligned loads & stores would discourage peeling relative to
unaligned accesses.
Thanks,
Richard
>
> * params.opt (--param=vect-aligned-ldst-cost-bias): New.
> * doc/invoke.texi (--param=vect-aligned-ldst-cost-bias): Document.
> * tree-vect-stmts.cc (vect_get_store_cost): Honor
> param_vect_aligned_ldst_cost_bias.
> (vect_get_load_cost): Likewise.
>
> * gcc.dg/vect/pr115843.c: Use it.
> ---
> gcc/doc/invoke.texi | 4 ++++
> gcc/params.opt | 4 ++++
> gcc/testsuite/gcc.dg/vect/pr115843.c | 1 +
> gcc/tree-vect-stmts.cc | 2 ++
> 4 files changed, 11 insertions(+)
>
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index 1360cae3986..e542cefbb4a 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -16914,6 +16914,10 @@ permit performing redundancy elimination after
> reload.
> The maximum number of insns in loop header duplicated
> by the copy loop headers pass.
>
> +@item vect-aligned-ldst-cost-bias
> +Bias to apply to the cost of aligned loads and stores. This
> +is useful for debugging only.
> +
> @item vect-epilogues-nomask
> Enable loop epilogue vectorization using smaller vector size.
>
> diff --git a/gcc/params.opt b/gcc/params.opt
> index 3c4369fa052..5f86d564421 100644
> --- a/gcc/params.opt
> +++ b/gcc/params.opt
> @@ -1166,6 +1166,10 @@ Use direct poisoning/unpoisoning instructions for
> variables smaller or equal to
> Common Joined UInteger Var(param_use_canonical_types) Init(1)
> IntegerRange(0, 1) Param
> Whether to use canonical types.
>
> +-param=vect-aligned-ldst-cost-bias=
> +Common Joined UInteger Var(param_vect_aligned_ldst_cost_bias) Init(0) Param
> Optimization
> +Bias to apply to the cost of aligned loads and stores.
> +
> -param=vect-epilogues-nomask=
> Common Joined UInteger Var(param_vect_epilogues_nomask) Init(1)
> IntegerRange(0, 1) Param Optimization
> Enable loop epilogue vectorization using smaller vector size.
> diff --git a/gcc/testsuite/gcc.dg/vect/pr115843.c
> b/gcc/testsuite/gcc.dg/vect/pr115843.c
> index 1b3fe277209..6701fa3499a 100644
> --- a/gcc/testsuite/gcc.dg/vect/pr115843.c
> +++ b/gcc/testsuite/gcc.dg/vect/pr115843.c
> @@ -1,3 +1,4 @@
> +/* { dg-additional-options "--param vect-aligned-ldst-cost-bias=100" } */
> /* { dg-additional-options "-mavx512vl --param vect-partial-vector-usage=2"
> { target { avx512f_runtime && avx512vl } } } */
>
> #include "tree-vect.h"
> diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
> index fc02e84b4b4..2502dbd5413 100644
> --- a/gcc/tree-vect-stmts.cc
> +++ b/gcc/tree-vect-stmts.cc
> @@ -997,6 +997,7 @@ vect_get_store_cost (vec_info *, stmt_vec_info stmt_info,
> int ncopies,
> *inside_cost += record_stmt_cost (body_cost_vec, ncopies,
> vector_store, stmt_info, 0,
> vect_body);
> + *inside_cost += param_vect_aligned_ldst_cost_bias * ncopies;
>
> if (dump_enabled_p ())
> dump_printf_loc (MSG_NOTE, vect_location,
> @@ -1049,6 +1050,7 @@ vect_get_load_cost (vec_info *, stmt_vec_info
> stmt_info, int ncopies,
> {
> *inside_cost += record_stmt_cost (body_cost_vec, ncopies, vector_load,
> stmt_info, 0, vect_body);
> + *inside_cost += param_vect_aligned_ldst_cost_bias * ncopies;
>
> if (dump_enabled_p ())
> dump_printf_loc (MSG_NOTE, vect_location,
