Tighten tree-ssa-ccp.c:get_value_for_expr condition

[Richard Sandiford]

bit_value_unop and bit_value_binop require constant values
to be INTEGER_CSTs:

  gcc_assert ((rval.lattice_val == CONSTANT
               && TREE_CODE (rval.value) == INTEGER_CST)
              || wi::sext (rval.mask, TYPE_PRECISION (TREE_TYPE (rhs))) == -1);

However, when deciding whether to record a constant value,
the for_bits_p handling in get_value_for_expr used a negative
test for ADDR_EXPR:

  else if (is_gimple_min_invariant (expr)
           && (!for_bits_p || TREE_CODE (expr) != ADDR_EXPR))

This patch uses a positive test for INTEGER_CST instead.

Existing tests showed the need for this once polynomial constants
are added.

Tested on aarch64-linux-gnu, x86_64-linux-gnu and powerpc64le-linus-gnu.
OK to install?

Richard


2017-09-20  Richard Sandiford  <richard.sandif...@linaro.org>
            Alan Hayward  <alan.hayw...@arm.com>
            David Sherwood  <david.sherw...@arm.com>

gcc/
        * tree-ssa-ccp.c (get_value_for_expr): Use a positive test for
        INTEGER_CST rather than a negative test for ADDR_EXPR.

Index: gcc/tree-ssa-ccp.c
===================================================================
--- gcc/tree-ssa-ccp.c  2017-08-10 14:36:07.842479033 +0100
+++ gcc/tree-ssa-ccp.c  2017-09-20 13:10:31.466004578 +0100
@@ -617,7 +617,7 @@ get_value_for_expr (tree expr, bool for_
        }
     }
   else if (is_gimple_min_invariant (expr)
-          && (!for_bits_p || TREE_CODE (expr) != ADDR_EXPR))
+          && (!for_bits_p || TREE_CODE (expr) == INTEGER_CST))
     {
       val.lattice_val = CONSTANT;
       val.value = expr;