Reapply "Initial implementation of on-stack replacement (OSR)."

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 fddde8096132e78a4fdb1563cd92a257a605f72d..d878f8d276536482541beb591e10d3352d2d84b9 100644
--- a/runtime/vm/flow_graph_allocator.cc
+++ b/runtime/vm/flow_graph_allocator.cc
@@ -510,16 +510,7 @@ void FlowGraphAllocator::BuildLiveRanges() {
         Definition* defn = (*catch_entry->initial_definitions())[i];
         LiveRange* range = GetLiveRange(defn->ssa_temp_index());
         range->DefineAt(catch_entry->start_pos());  // Defined at block entry.
-
-        // Save range->End() because it may change in ProcessInitialDefinition.
-        intptr_t range_end = range->End();
         ProcessInitialDefinition(defn, range, catch_entry);
-        spill_slots_.Add(range_end);
-        quad_spill_slots_.Add(false);
-
-        if (defn->IsParameter() && range->spill_slot().stack_index() >= 0) {
-          MarkAsObjectAtSafepoints(range);
-        }
       }
     }
   }
@@ -532,16 +523,7 @@ void FlowGraphAllocator::BuildLiveRanges() {
     LiveRange* range = GetLiveRange(defn->ssa_temp_index());
     range->AddUseInterval(graph_entry->start_pos(), graph_entry->end_pos());
     range->DefineAt(graph_entry->start_pos());
-
-    // Save range->End() because it may change in ProcessInitialDefinition.
-    intptr_t range_end = range->End();
     ProcessInitialDefinition(defn, range, graph_entry);
-    if (defn->IsParameter() && flow_graph_.num_copied_params() > 0) {
-      spill_slots_.Add(range_end);
-      quad_spill_slots_.Add(false);
-
-      MarkAsObjectAtSafepoints(range);
-    }
   }
 }
 
@@ -549,6 +531,8 @@ void FlowGraphAllocator::BuildLiveRanges() {
 void FlowGraphAllocator::ProcessInitialDefinition(Definition* defn,
                                                   LiveRange* range,
                                                   BlockEntryInstr* block) {
+  // Save the range end because it may change below.
+  intptr_t range_end = range->End();
   if (defn->IsParameter()) {
     ParameterInstr* param = defn->AsParameter();
     // Assert that copied and non-copied parameters are mutually exclusive.
@@ -579,6 +563,17 @@ void FlowGraphAllocator::ProcessInitialDefinition(Definition* defn,
     CompleteRange(tail, Location::kRegister);
   }
   ConvertAllUses(range);
+  if (defn->IsParameter() && (range->spill_slot().stack_index() >= 0)) {
+    // Parameters above the frame pointer consume spill slots and are marked
+    // in stack maps.
+    spill_slots_.Add(range_end);
+    quad_spill_slots_.Add(false);
+    MarkAsObjectAtSafepoints(range);
+  } else if (defn->IsConstant() && block->IsCatchBlockEntry()) {
+    // Constants at catch block entries consume spill slots.
+    spill_slots_.Add(range_end);
+    quad_spill_slots_.Add(false);
+  }
 }
 
 
@@ -1617,7 +1612,6 @@ void FlowGraphAllocator::AllocateSpillSlotFor(LiveRange* range) {
     }
   }
 
-
   // Set spill slot expiration boundary to the live range's end.
   spill_slots_[idx] = end;
   if (need_quad) {