https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107863
--- Comment #9 from Hongtao.liu <crazylht at gmail dot com> ---
expand_expr_real_1 generates (const_int 255) without considering the target
mode.
I guess it's on purpose, so I'll leave that alone and only change the expander
in the backend. After applying convert_modes to (const_int 255), it's
transformed to (const_int -1) which should fix the issue.
-----------cut from expand_expr_real_1--------------
11010 case INTEGER_CST:
11011 {
11012 /* Given that TYPE_PRECISION (type) is not always equal to
11013 GET_MODE_PRECISION (TYPE_MODE (type)), we need to extend from
11014 the former to the latter according to the signedness of the
11015 type. */
11016 scalar_int_mode int_mode = SCALAR_INT_TYPE_MODE (type);
11017 temp = immed_wide_int_const
11018 (wi::to_wide (exp, GET_MODE_PRECISION (int_mode)), int_mode);
11019 return temp;
11020 }
-----------cut ends------------------------
Proposed patch:
diff --git a/gcc/config/i386/i386-expand.cc b/gcc/config/i386/i386-expand.cc
index 0373c3614a4..c639ee3a9f7 100644
--- a/gcc/config/i386/i386-expand.cc
+++ b/gcc/config/i386/i386-expand.cc
@@ -12475,7 +12475,7 @@ ix86_expand_vec_set_builtin (tree exp)
op1 = expand_expr (arg1, NULL_RTX, mode1, EXPAND_NORMAL);
elt = get_element_number (TREE_TYPE (arg0), arg2);
- if (GET_MODE (op1) != mode1 && GET_MODE (op1) != VOIDmode)
+ if (GET_MODE (op1) != mode1)
op1 = convert_modes (mode1, GET_MODE (op1), op1, true);
op0 = force_reg (tmode, op0);
