Make all variants of RelationalOp work with SSA.

runtime/vm/flow_graph_allocator.cc

Index: runtime/vm/flow_graph_allocator.cc
===================================================================
--- runtime/vm/flow_graph_allocator.cc	(revision 10728)
+++ runtime/vm/flow_graph_allocator.cc	(working copy)
@@ -744,10 +744,8 @@
 
   LocationSummary* locs = current->locs();
 
-  // TODO(vegorov): number of inputs must match number of input locations.
-  if (locs->input_count() != current->InputCount()) {
-    builder_->Bailout("ssa allocator: number of input locations mismatch");
-  }
+  // Number of input locations and number of input operands have to agree.
+  ASSERT(locs->input_count() == current->InputCount());
 
   // Normalize same-as-first-input output if input is specified as
   // fixed register.