[Patch, vrp] Allow VRP type conversion folding only for widenings upto word mode

[Senthil Kumar Selvaraj]

This patch came out of a discussion held in the gcc mailing list
(https://gcc.gnu.org/ml/gcc/2015-11/msg00067.html).

The patch restricts folding of conditional exprs with lhs previously
set by a type conversion to occur only if the source of the type 
conversion's mode is word mode or smaller.

Bootstrapped and reg tested on x86_64 (with --enable-languages=c,c++).

If ok, could you commit please? I don't have commit access.

Regards
Senthil

gcc/ChangeLog

2015-11-11  Senthil Kumar Selvaraj  <senthil_kumar.selva...@atmel.com>

        * tree-vrp.c (simplify_cond_using_ranges): Fold only
        if innerop's mode is word_mode or smaller.


diff --git gcc/tree-vrp.c gcc/tree-vrp.c
index e2393e4..c139bc6 100644
--- gcc/tree-vrp.c
+++ gcc/tree-vrp.c
@@ -9467,6 +9467,8 @@ simplify_cond_using_ranges (gcond *stmt)
       innerop = gimple_assign_rhs1 (def_stmt);
 
       if (TREE_CODE (innerop) == SSA_NAME
+         && (GET_MODE_SIZE(TYPE_MODE(TREE_TYPE(innerop))) 
+           <= GET_MODE_SIZE(word_mode))
          && !POINTER_TYPE_P (TREE_TYPE (innerop)))
        {
          value_range *vr = get_value_range (innerop);