vect: Reject non-byte offsets for gather/scatters [PR107346]

The ada failure reported in the PR was being caused by vect_check_gather_scatter
failing to deal with bit offsets that weren't multiples of BITS_PER_UNIT. This
patch makes vect_check_gather_scatter reject memory accesses with such offsets.

gcc/ChangeLog:

	PR tree-optimization/107346
	* tree-vect-data-refs.cc (vect_check_gather_scatter): Reject offsets
	that aren't multiples of BITS_PER_UNIT.

diff --git a/gcc/tree-vect-data-refs.cc b/gcc/tree-vect-data-refs.cc
index 4a23d61..6c89279 100644 (file)
--- a/gcc/tree-vect-data-refs.cc
+++ b/gcc/tree-vect-data-refs.cc
@@ -4016,6 +4016,11 @@ vect_check_gather_scatter (stmt_vec_info stmt_info, loop_vec_info loop_vinfo,
   if (reversep)
     return false;
 
+  /* PR 107346.  Packed structs can have fields at offsets that are not
+     multiples of BITS_PER_UNIT.  Do not use gather/scatters in such cases.  */
+  if (!multiple_p (pbitpos, BITS_PER_UNIT))
+    return false;
+
   poly_int64 pbytepos = exact_div (pbitpos, BITS_PER_UNIT);
 
   if (TREE_CODE (base) == MEM_REF)