[gcc r17-2683] Remove shift vectorization check from vect_build_slp_tree_1

https://gcc.gnu.org/g:a3a3e4fa672a5d925f303440345a62925fb5f5e8

commit r17-2683-ga3a3e4fa672a5d925f303440345a62925fb5f5e8
Author: Richard Biener <[email protected]>
Date:   Fri Jul 24 09:21:50 2026 +0200

    Remove shift vectorization check from vect_build_slp_tree_1
    
    The following removes the SLP discovery failure caused by not
    vectorizable shifts.  This does not belong here.  I have kept
    the heuristic that forces uniform shift operands when vector-vector
    shifts are not supported.
    
            * tree-vect-slp.cc (vect_build_slp_tree_1): Remove failure
            on unvectorizable shifts.

Diff:
---
 gcc/tree-vect-slp.cc | 18 ++++--------------
 1 file changed, 4 insertions(+), 14 deletions(-)

diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
index dcd35da43a29..cc802f4f4cd9 100644
--- a/gcc/tree-vect-slp.cc
+++ b/gcc/tree-vect-slp.cc
@@ -1327,26 +1327,16 @@ vect_build_slp_tree_1 (vec_info *vinfo, unsigned char *swap,
 
 	  /* Shift arguments should be equal in all the packed stmts for a
 	     vector shift with scalar shift operand.  */
-	  if (rhs_code == LSHIFT_EXPR || rhs_code == RSHIFT_EXPR
+	  if (rhs_code == LSHIFT_EXPR
+	      || rhs_code == RSHIFT_EXPR
 	      || rhs_code == LROTATE_EXPR
 	      || rhs_code == RROTATE_EXPR)
 	    {
 	      /* First see if we have a vector/vector shift.  */
 	      if (!directly_supported_p (rhs_code, vectype, optab_vector))
 		{
-		  /* No vector/vector shift, try for a vector/scalar shift.  */
-		  if (!directly_supported_p (rhs_code, vectype, optab_scalar))
-		    {
-		      if (dump_enabled_p ())
-			dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
-					 "Build SLP failed: "
-					 "op not supported by target.\n");
-		      if (is_a <bb_vec_info> (vinfo) && i != 0)
-			continue;
-		      /* Fatal mismatch.  */
-		      matches[0] = false;
-		      return false;
-		    }
+		  /* No vector/vector shift, arrange for a vector/scalar
+		     SLP layout.  */
 		  need_same_oprnds = true;
 		  first_op1 = gimple_assign_rhs2 (stmt);
 		}