VM: Fix frame size computation for optimized DBC code

runtime/vm/flow_graph_allocator.cc

Index: runtime/vm/flow_graph_allocator.cc
diff --git a/runtime/vm/flow_graph_allocator.cc b/runtime/vm/flow_graph_allocator.cc
index 4778d7a79642f465bf4e7b4afb9590679d607dfa..009e500bb88e655a793046269450829bf7a62c01 100644
--- a/runtime/vm/flow_graph_allocator.cc
+++ b/runtime/vm/flow_graph_allocator.cc
@@ -441,6 +441,10 @@ void FlowGraphAllocator::BlockLocation(Location loc,
                                        intptr_t to) {
   if (loc.IsRegister()) {
     BlockRegisterLocation(loc, from, to, blocked_cpu_registers_, cpu_regs_);
+#if defined(TARGET_ARCH_DBC)
+    last_used_register_ = Utils::Maximum(last_used_register_,
+                                         loc.register_code());
+#endif
   } else if (loc.IsFpuRegister()) {
     BlockRegisterLocation(loc, from, to, blocked_fpu_registers_, fpu_regs_);
   } else {
@@ -2742,10 +2746,6 @@ void FlowGraphAllocator::PrepareForAllocation(
       registers_[reg]->Add(range);
     }
   }
-
-#if defined(TARGET_ARCH_DBC)
-  last_used_register_ = -1;
-#endif
 }
 
 
@@ -3010,6 +3010,10 @@ void FlowGraphAllocator::AllocateRegisters() {
 
   DiscoverLoops();
 
+#if defined(TARGET_ARCH_DBC)
+  last_used_register_ = -1;
+#endif
+
   BuildLiveRanges();
 
   if (FLAG_print_ssa_liveranges) {
@@ -3038,6 +3042,7 @@ void FlowGraphAllocator::AllocateRegisters() {
   AllocateUnallocatedRanges();
 #if defined(TARGET_ARCH_DBC)
   const intptr_t last_used_cpu_register = last_used_register_;
+  last_used_register_ = -1;
 #endif
 
   cpu_spill_slot_count_ = spill_slots_.length();