Reapply "Added support for copied parameters to the SSA compiler."

runtime/vm/flow_graph_builder.cc

Index: runtime/vm/flow_graph_builder.cc
diff --git a/runtime/vm/flow_graph_builder.cc b/runtime/vm/flow_graph_builder.cc
index 726487b1bcb7d07fe51d3914819cd44349a74c7f..221cdcb06565848917cd6f141932258a09c3d03f 100644
--- a/runtime/vm/flow_graph_builder.cc
+++ b/runtime/vm/flow_graph_builder.cc
@@ -2297,11 +2297,21 @@ void FlowGraphBuilder::BuildGraph(bool for_optimized, bool use_ssa) {
   GrowableArray<intptr_t> parent;
   GrowableArray<BitVector*> assigned_vars;
 
-  const intptr_t fixed_parameter_count =
-      parsed_function_.function().num_fixed_parameters();
-  const intptr_t variable_count = fixed_parameter_count +
-      parsed_function_.copied_parameter_count() +
-      parsed_function_.stack_local_count();
+  // Either all parameters are fixed (none are named) or they are all copied.
+  // This could change, so we keep fixed/copied counts separate.
+  intptr_t fixed_parameter_count;  // This is really the "non-copied" count.
+  intptr_t copied_parameter_count;
+  if (parsed_function_.copied_parameter_count() > 0) {
+    fixed_parameter_count = 0;
+    copied_parameter_count = parsed_function_.copied_parameter_count();
+  } else {
+    fixed_parameter_count = parsed_function_.function().num_fixed_parameters();
+    copied_parameter_count = 0;
+  }
+  const intptr_t stack_local_count = parsed_function_.stack_local_count();
+  const intptr_t variable_count =
+      stack_local_count + fixed_parameter_count + copied_parameter_count;
+
   // Perform a depth-first traversal of the graph to build preorder and
   // postorder block orders.
   graph_entry_->DiscoverBlocks(NULL,  // Entry block predecessor.
@@ -2337,7 +2347,7 @@ void FlowGraphBuilder::BuildGraph(bool for_optimized, bool use_ssa) {
                assigned_vars,
                variable_count,
                dominance_frontier);
-    Rename(variable_count);
+    Rename(stack_local_count, fixed_parameter_count, copied_parameter_count);
   }
   if (FLAG_print_flow_graph || (Dart::flow_graph_writer() != NULL)) {
     intptr_t length = postorder_block_entries_.length();
@@ -2539,26 +2549,24 @@ void FlowGraphBuilder::InsertPhis(
 }
 
 
-void FlowGraphBuilder::Rename(intptr_t var_count) {
-  // TODO(fschneider): Store var_count in the FlowGraphBuilder instead of
+void FlowGraphBuilder::Rename(intptr_t stack_local_count,
+                              intptr_t fixed_parameter_count,
+                              intptr_t copied_parameter_count) {
+  // TODO(fschneider): Store counts in the FlowGraphBuilder instead of
   // passing it around.
   // TODO(fschneider): Support catch-entry.
   if (graph_entry_->SuccessorCount() > 1) {
     Bailout("Catch-entry support in SSA.");
   }
-  // TODO(fschneider): Support copied parameters.
-  if (parsed_function().copied_parameter_count() != 0) {
-    Bailout("Copied parameter support in SSA");
-  }
-  ASSERT(var_count == (parsed_function().stack_local_count() +
-                       parsed_function().function().num_fixed_parameters()));
+
+  const intptr_t parameter_count =
+      fixed_parameter_count + copied_parameter_count;
+  const intptr_t variable_count = parameter_count + stack_local_count;
 
   // Initialize start environment.
-  GrowableArray<Value*> start_env(var_count);
+  GrowableArray<Value*> start_env(variable_count);
   intptr_t i = 0;
-  const intptr_t fixed_parameter_count =
-      parsed_function().function().num_fixed_parameters();
-  for (; i < fixed_parameter_count; ++i) {
+  for (; i < parameter_count; ++i) {
     ParameterInstr* param = new ParameterInstr(i);
     param->set_ssa_temp_index(alloc_ssa_temp_index());  // New SSA temp.
     start_env.Add(new UseVal(param));
@@ -2566,7 +2574,7 @@ void FlowGraphBuilder::Rename(intptr_t var_count) {
 
   // All locals are initialized with #null.
   Value* null_value = new ConstantVal(Object::ZoneHandle());
-  for (; i < var_count; i++) {
+  for (; i < variable_count; i++) {
     start_env.Add(null_value);
   }
   graph_entry_->set_start_env(
@@ -2574,9 +2582,9 @@ void FlowGraphBuilder::Rename(intptr_t var_count) {
 
   BlockEntryInstr* normal_entry = graph_entry_->SuccessorAt(0);
   ASSERT(normal_entry != NULL);  // Must have entry.
-  GrowableArray<Value*> env(var_count);
+  GrowableArray<Value*> env(variable_count);
   env.AddArray(start_env);
-  RenameRecursive(normal_entry, &env, var_count, fixed_parameter_count);
+  RenameRecursive(normal_entry, &env, variable_count, fixed_parameter_count);
 }