Fix unguarded use of tree_to_shwi in tree-ssa-sccvn.c

[Richard Sandiford]

Fixes many testsuite failures for SVE.

Tested on aarch64-linux-gnu (with and without SVE), aarch64_be-elf
and x86_64-linux-gnu.  OK to install?

Richard


2018-08-28  Richard Sandiford  <richard.sandif...@arm.com>

gcc/
        * tree-ssa-sccvn.c (fully_constant_vn_reference_p): Fix unguarded
        use of tree_to_shwi.  Remove duplicated test for the size being
        a whole number of bytes.

Index: gcc/tree-ssa-sccvn.c
===================================================================
--- gcc/tree-ssa-sccvn.c        2018-08-28 11:38:22.000000000 +0100
+++ gcc/tree-ssa-sccvn.c        2018-08-28 11:38:22.676512354 +0100
@@ -1409,16 +1409,16 @@ fully_constant_vn_reference_p (vn_refere
   /* Simplify reads from constants or constant initializers.  */
   else if (BITS_PER_UNIT == 8
           && COMPLETE_TYPE_P (ref->type)
-          && is_gimple_reg_type (ref->type)
-          && (!INTEGRAL_TYPE_P (ref->type)
-              || TYPE_PRECISION (ref->type) % BITS_PER_UNIT == 0))
+          && is_gimple_reg_type (ref->type))
     {
       poly_int64 off = 0;
       HOST_WIDE_INT size;
       if (INTEGRAL_TYPE_P (ref->type))
        size = TYPE_PRECISION (ref->type);
-      else
+      else if (tree_fits_shwi_p (TYPE_SIZE (ref->type)))
        size = tree_to_shwi (TYPE_SIZE (ref->type));
+      else
+       return NULL_TREE;
       if (size % BITS_PER_UNIT != 0
          || size > MAX_BITSIZE_MODE_ANY_MODE)
        return NULL_TREE;