[PATCH Obvious/r236200]Check invariant expression pointer, not pointer to the pointer

[PATCH Obvious/r236200]Check invariant expression pointer, not pointer to the pointer

[Bin Cheng]

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Hi,
Revision 236200 checks wrong pointer for invariant expression, which accidentally clears all depends_on information.  This causes wrong cost and bad code generation, for example, gcc.target/arm/pr42505.c on thumb1 targets.  This patch fixes the issue.
Test result checked for gcc.target/arm/pr42505.c.  Apply as obvious.

Thanks,
bin

2016-05-18 Bin Cheng  <bin.cheng@arm.com>

	* tree-ssa-loop-ivopts.c (get_computation_cost_at): Check invariant
	expression pointer, not pointer to the pointer.

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diff --git a/gcc/tree-ssa-loop-ivopts.c b/gcc/tree-ssa-loop-ivopts.c
index e8953a0..9ce6b64 100644
--- a/gcc/tree-ssa-loop-ivopts.c
+++ b/gcc/tree-ssa-loop-ivopts.c
@@ -4874,7 +4874,7 @@ get_computation_cost_at (struct ivopts_data *data,
       *inv_expr = get_loop_invariant_expr (data, ubase, cbase, ratio,
 					   address_p);
       /* Clear depends on.  */
-      if (inv_expr != NULL)
+      if (*inv_expr != NULL)
 	bitmap_clear (*depends_on);
     }