[PATCH] vect: Use xor to invert oversized vector masks

[Andrew Stubbs]

Don't enable excess lanes when inverting vector bit-masks smaller than the
integer mode.  This is yet another case of wrong-code due to mishandling
of oversized bitmasks.

This issue shows up in vect/tsvc/vect-tsvc-s278.c and
vect/tsvc/vect-tsvc-s279.c if I set the preferred vector size to V32
(down from V64) on amdgcn.

OK for mainline?

Andrew

gcc/ChangeLog:

        * expr.cc (expand_expr_real_2): Use xor to invert vector masks.
---
 gcc/expr.cc | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/gcc/expr.cc b/gcc/expr.cc
index 403eeaa108e4..3540327d879e 100644
--- a/gcc/expr.cc
+++ b/gcc/expr.cc
@@ -10497,6 +10497,17 @@ expand_expr_real_2 (sepops ops, rtx target, 
machine_mode tmode,
                               immed_wide_int_const (mask, int_mode),
                               target, 1, OPTAB_LIB_WIDEN);
        }
+      /* If it's a vector mask don't enable excess bits.  */
+      else if (VECTOR_BOOLEAN_TYPE_P (type)
+              && SCALAR_INT_MODE_P (mode)
+              && maybe_ne (GET_MODE_PRECISION (mode),
+                           TYPE_VECTOR_SUBPARTS (type).to_constant ()))
+       {
+         auto nunits = TYPE_VECTOR_SUBPARTS (type).to_constant ();
+         temp = expand_binop (mode, xor_optab, op0,
+                              GEN_INT ((HOST_WIDE_INT_1U << nunits) - 1),
+                              target, true, OPTAB_WIDEN);
+       }
       else
        temp = expand_unop (mode, one_cmpl_optab, op0, target, 1);
       gcc_assert (temp);
-- 
2.41.0