Fix use of valgrind API

gcc/
	PR middle-end/67649
	* memory-block.h (memory_block_pool::allocate): Use valgrind API to
	mark the block as accessible.

From-SVN: r228033

gcc/ChangeLog

+2015-09-23  Mikhail Maltsev  <maltsevm@gmail.com>
+
+	PR middle-end/67649
+	* memory-block.h (memory_block_pool::allocate): Use valgrind API to
+	mark the block as accessible.
+
 2015-09-22  Segher Boessenkool  <segher@kernel.crashing.org>
 
 	* function.c (thread_prologue_and_epilogue_insns): Delete

gcc/memory-block.h

@@ -57,6 +57,7 @@ memory_block_pool::allocate ()
 
   void *result = instance.m_blocks;
   instance.m_blocks = instance.m_blocks->m_next;
+  VALGRIND_DISCARD (VALGRIND_MAKE_MEM_UNDEFINED (result, block_size));
   return result;
 }