[PATCH] Fix UB in ix86_expand_vector_init_one_var (PR target/85508)

[Jakub Jelinek]

Hi!

WHen INTVAL (x) is negative, this invokes UB, because left shift of negative
value is undefined in C++.

Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk?

2018-04-24  Jakub Jelinek  <ja...@redhat.com>

        PR target/85508
        * config/i386/i386.c (ix86_expand_vector_init_one_var): Use UINTVAL
        instead of INTVAL when shifting x left.

        * gcc.target/i386/pr85508.c: New test.

--- gcc/config/i386/i386.c.jj   2018-04-24 10:37:01.258882134 +0200
+++ gcc/config/i386/i386.c      2018-04-24 11:37:29.002706293 +0200
@@ -43200,7 +43200,7 @@ ix86_expand_vector_init_one_var (bool mm
       else
        {
          var = convert_modes (HImode, QImode, var, true);
-         x = gen_int_mode (INTVAL (x) << 8, HImode);
+         x = gen_int_mode (UINTVAL (x) << 8, HImode);
        }
       if (x != const0_rtx)
        var = expand_simple_binop (HImode, IOR, var, x, var,
--- gcc/testsuite/gcc.target/i386/pr85508.c.jj  2018-04-24 11:37:48.890721003 
+0200
+++ gcc/testsuite/gcc.target/i386/pr85508.c     2018-04-24 11:32:40.598491856 
+0200
@@ -0,0 +1,12 @@
+/* PR target/85508 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -msse2" } */
+
+typedef signed char V __attribute__((vector_size (16)));
+signed char c;
+
+V
+foo (void)
+{
+  return (V) { c, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 };
+}

        Jakub