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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/98849] [11 Regression] ICE in expand_shift_1, at
 expmed.c:2658 since g:7432f255b70811dafaf325d9403
Date: Wed, 27 Jan 2021 13:06:16 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98849

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
For #c2 I've tried:
--- gcc/tree-vect-generic.c.jj  2021-01-04 10:25:38.289239984 +0100
+++ gcc/tree-vect-generic.c     2021-01-27 13:53:28.457752505 +0100
@@ -2147,16 +2147,21 @@ expand_vector_operations_1 (gimple_stmt_
       || code =3D=3D LROTATE_EXPR
       || code =3D=3D RROTATE_EXPR)
     {
-      optab opv;
+      optab opv =3D optab_for_tree_code (code, type, optab_vector);

       /* Check whether we have vector <op> {x,x,x,x} where x
          could be a scalar variable or a constant.  Transform
-         vector <op> {x,x,x,x} =3D=3D> vector <op> scalar.  */
+         vector <op> {x,x,x,x} =3D=3D> vector <op> scalar, unless
+        the backend only supports vector <op> by vector and not
+        vecot <op> by scalar.  */
       if (VECTOR_INTEGER_TYPE_P (TREE_TYPE (rhs2)))
         {
           tree first;

-          if ((first =3D ssa_uniform_vector_p (rhs2)) !=3D NULL_TREE)
+          op =3D optab_for_tree_code (code, type, optab_scalar);
+          if ((first =3D ssa_uniform_vector_p (rhs2)) !=3D NULL_TREE
+             && (get_compute_type (code, opv, type) !=3D type
+                 || get_compute_type (code, op, type) =3D=3D type))
             {
               gimple_assign_set_rhs2 (stmt, first);
               update_stmt (stmt);
@@ -2164,7 +2169,6 @@ expand_vector_operations_1 (gimple_stmt_
             }
         }

-      opv =3D optab_for_tree_code (code, type, optab_vector);
       if (VECTOR_INTEGER_TYPE_P (TREE_TYPE (rhs2)))
        op =3D opv;
       else
but that doesn't really help, because while veclower21 doesn't undo what the
vectorizer carefully did, match.pd during fre5 breaks it again:
 /* Prefer vector1 << scalar to vector1 << vector2
    if vector2 is uniform.  */
 (for vec (VECTOR_CST CONSTRUCTOR)
  (simplify
   (shiftrotate @0 vec@1)
   (with { tree tem =3D uniform_vector_p (@1); }
    (if (tem)
     (shiftrotate @0 { tem; }))))))

So, does ARM really only have vector shifts and not scalar?
Though, PowerPC seems to have that too, I'll check out what it does on these
testcases.=