[PATCH] Fix ICE on CONST_WIDE_INT in simplify_immed_subreg (PR rtl-optimization/78526)

[Jakub Jelinek]

Hi!

If we try to simplify a paradoxical subreg of a CONST_WIDE_INT,
we can ICE, because wi::extract_uhwi doesn't like accessing
bytes beyond the precision.
  for (i = 0; i < elem_bitsize; i += value_bit)
    *vp++ = wi::extract_uhwi (val, i, value_bit);
  for (; i < elem_bitsize; i += value_bit)
    *vp++ = extend;
looks wrong, because the second loop is useless.  But, we actually
do want the second loop, to handle the paradoxical bytes.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2016-11-25  Jakub Jelinek  <ja...@redhat.com>

        PR rtl-optimization/78526
        * simplify-rtx.c (simplify_immed_subreg): Don't use wi::extract_uhwi
        beyond val's precision.

        * gcc.dg/pr78526.c: New test.

--- gcc/simplify-rtx.c.jj       2016-11-18 20:04:28.000000000 +0100
+++ gcc/simplify-rtx.c  2016-11-25 15:07:13.872322389 +0100
@@ -5740,8 +5740,9 @@ simplify_immed_subreg (machine_mode oute
          {
            rtx_mode_t val = rtx_mode_t (el, innermode);
            unsigned char extend = wi::sign_mask (val);
+           int prec = wi::get_precision (val);
 
-           for (i = 0; i < elem_bitsize; i += value_bit)
+           for (i = 0; i < prec && i < elem_bitsize; i += value_bit)
              *vp++ = wi::extract_uhwi (val, i, value_bit);
            for (; i < elem_bitsize; i += value_bit)
              *vp++ = extend;
--- gcc/testsuite/gcc.dg/pr78526.c.jj   2016-11-25 15:15:53.266799450 +0100
+++ gcc/testsuite/gcc.dg/pr78526.c      2016-11-25 15:16:12.004564146 +0100
@@ -0,0 +1,21 @@
+/* PR rtl-optimization/78526 */
+/* { dg-do compile { target int128 } } */
+/* { dg-options "-O -fno-tree-ccp -fno-tree-sra -g -w" } */
+/* { dg-additional-options "-mavx512bw" { target i?86-*-* x86_64-*-* } } */
+
+typedef unsigned U __attribute__ ((vector_size (64)));
+typedef unsigned __int128 V __attribute__ ((vector_size (64)));
+
+static inline V
+bar (U u, U x, V v)
+{
+  v = (V)(U) { 0, ~0 };
+  v[x[0]] <<= u[-63];
+  return v;
+}
+
+V
+foo (U u)
+{
+  return bar (u, (U) {}, (V) {});
+}

        Jakub