Re: [PATCH] tree-optimization/105175 - avoid -Wvector-operation-performance

[Martin Sebor via Gcc-patches]

On 4/6/22 03:23, Richard Biener wrote:

This avoids -Wvector-operation-performance diagnostics for vectorizer
produced code.  It's unfortunate the warning_at code in
tree-vect-generic.cc needs adjustments but the diagnostic suppression
code doesn't magically suppress those otherwise.

It seems like it should, as long as the statement location hasn't
changed after the suppress_diagnostic call in tree-vect-stmts.cc.

Bootstrap / regtest running on x86_64-unknown-linux-gnu.

Martin/David - did I miss something obvious when doing the
tree-vect-generic.cc adjustment?

The only thing I can think of is that because it's not handled in
diagnostic-spec.cc, -Wvector-operation-performance is lumped in with
all other generic warnings that also aren't handled.  It means that
they are all treated as a group.  Whether or not that's what we want
for this specific warning might be something to consider.

Martin

Thanks,
Richard.

2022-04-06  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/105175
        * tree-vect-stmts.cc (vectorizable_operation): Suppress
        -Wvector-operation-performance if using emulated vectors.
        * tree-vect-generic.cc (expand_vector_piecewise): Do not diagnose
        -Wvector-operation-performance when suppressed.
        (expand_vector_parallel): Likewise.
        (expand_vector_comparison): Likewise.
        (expand_vector_condition): Likewise.
        (lower_vec_perm): Likewise.
        (expand_vector_conversion): Likewise.

        * gcc.dg/pr105175.c: New testcase.
---
  gcc/testsuite/gcc.dg/pr105175.c | 16 +++++++++++++
  gcc/tree-vect-generic.cc        | 41 ++++++++++++++++++++++-----------
  gcc/tree-vect-stmts.cc          |  2 ++
  3 files changed, 45 insertions(+), 14 deletions(-)
  create mode 100644 gcc/testsuite/gcc.dg/pr105175.c

diff --git a/gcc/testsuite/gcc.dg/pr105175.c b/gcc/testsuite/gcc.dg/pr105175.c
new file mode 100644
index 00000000000..d8d7edb942a
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr105175.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -Wvector-operation-performance" } */
+/* { dg-additional-options "-mno-sse" { target x86_64-*-* i?86-*-* } } */
+
+enum { QEMU_MIGRATION_COOKIE_PERSISTENT = 1 };
+struct {
+  unsigned flags;
+  unsigned flagsMandatory;
+} qemuMigrationCookieGetPersistent_mig;
+void qemuMigrationCookieGetPersistent()
+{
+  qemuMigrationCookieGetPersistent_mig.flags &=  /* { dg-bogus "will be 
expanded" } */
+      QEMU_MIGRATION_COOKIE_PERSISTENT;
+  qemuMigrationCookieGetPersistent_mig.flagsMandatory &=
+      QEMU_MIGRATION_COOKIE_PERSISTENT;
+}
diff --git a/gcc/tree-vect-generic.cc b/gcc/tree-vect-generic.cc
index 12a553ec8be..8b7227e8b58 100644
--- a/gcc/tree-vect-generic.cc
+++ b/gcc/tree-vect-generic.cc
@@ -317,8 +317,11 @@ expand_vector_piecewise (gimple_stmt_iterator *gsi, 
elem_op_func f,
    int i;
    location_t loc = gimple_location (gsi_stmt (*gsi));

- if (nunits == 1)

-    /* Do not diagnose decomposing single element vectors.  */
+  if (nunits == 1
+      || warning_suppressed_p (gsi_stmt (*gsi),
+                              OPT_Wvector_operation_performance))
+    /* Do not diagnose decomposing single element vectors or when
+       decomposing vectorizer produced operations.  */
      ;
    else if (ret_type || !parallel_p)
      warning_at (loc, OPT_Wvector_operation_performance,
@@ -379,14 +382,16 @@ expand_vector_parallel (gimple_stmt_iterator *gsi, 
elem_op_func f, tree type,
    else
      {
        /* Use a single scalar operation with a mode no wider than word_mode.  
*/
+      if (!warning_suppressed_p (gsi_stmt (*gsi),
+                                OPT_Wvector_operation_performance))
+       warning_at (loc, OPT_Wvector_operation_performance,
+                   "vector operation will be expanded with a "
+                   "single scalar operation");
        scalar_int_mode mode
        = int_mode_for_size (tree_to_uhwi (TYPE_SIZE (type)), 0).require ();
        compute_type = lang_hooks.types.type_for_mode (mode, 1);
        result = f (gsi, compute_type, a, b, bitsize_zero_node,
                  TYPE_SIZE (compute_type), code, type);
-      warning_at (loc, OPT_Wvector_operation_performance,
-                 "vector operation will be expanded with a "
-                 "single scalar operation");
      }

return result;

@@ -487,8 +492,10 @@ expand_vector_comparison (gimple_stmt_iterator *gsi, tree 
type, tree op0,

if (TYPE_PRECISION (ret_inner_type) != 1)

            ret_inner_type = build_nonstandard_integer_type (1, 1);
-         warning_at (loc, OPT_Wvector_operation_performance,
-                     "vector operation will be expanded piecewise");
+         if (!warning_suppressed_p (gsi_stmt (*gsi),
+                                    OPT_Wvector_operation_performance))
+           warning_at (loc, OPT_Wvector_operation_performance,
+                       "vector operation will be expanded piecewise");
          for (i = 0; i < nunits;
               i++, index = int_const_binop (PLUS_EXPR, index, part_width))
            {
@@ -1098,8 +1105,9 @@ expand_vector_condition (gimple_stmt_iterator *gsi, 
bitmap dce_ssa_names)

/* TODO: try and find a smaller vector type. */ - warning_at (loc, OPT_Wvector_operation_performance,

-             "vector condition will be expanded piecewise");
+  if (!warning_suppressed_p (stmt, OPT_Wvector_operation_performance))
+    warning_at (loc, OPT_Wvector_operation_performance,
+               "vector condition will be expanded piecewise");

if (!a_is_comparison

        && VECTOR_BOOLEAN_TYPE_P (TREE_TYPE (a))
@@ -1591,9 +1599,10 @@ lower_vec_perm (gimple_stmt_iterator *gsi)
      }
    else if (can_vec_perm_var_p (TYPE_MODE (vect_type)))
      return;
-
-  warning_at (loc, OPT_Wvector_operation_performance,
-              "vector shuffling operation will be expanded piecewise");
+
+  if (!warning_suppressed_p (stmt, OPT_Wvector_operation_performance))
+    warning_at (loc, OPT_Wvector_operation_performance,
+               "vector shuffling operation will be expanded piecewise");

vec_alloc (v, elements);

    bool constant_p = true;
@@ -2029,8 +2038,12 @@ expand_vector_conversion (gimple_stmt_iterator *gsi)
              location_t loc = gimple_location (gsi_stmt (*gsi));

if (compute_type != arg_type)

-               warning_at (loc, OPT_Wvector_operation_performance,
-                           "vector operation will be expanded piecewise");
+               {
+                 if (!warning_suppressed_p (gsi_stmt (*gsi),
+                                            OPT_Wvector_operation_performance))
+                   warning_at (loc, OPT_Wvector_operation_performance,
+                               "vector operation will be expanded piecewise");
+               }
              else
                {
                  nunits = 1;
diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
index 29d6b2a2ae7..3f8d5aac8ee 100644
--- a/gcc/tree-vect-stmts.cc
+++ b/gcc/tree-vect-stmts.cc
@@ -6456,6 +6456,8 @@ vectorizable_operation (vec_info *vinfo,
          new_temp = make_ssa_name (vec_dest, new_stmt);
          gimple_assign_set_lhs (new_stmt, new_temp);
          vect_finish_stmt_generation (vinfo, stmt_info, new_stmt, gsi);
+         if (using_emulated_vectors_p)
+           suppress_warning (new_stmt, OPT_Wvector_operation_performance);

/* Enter the combined value into the vector cond hash so we don't

             AND it with a loop mask again.  */