Build and use stack maps in the SSA compiler.

runtime/vm/flow_graph_allocator.h

Index: runtime/vm/flow_graph_allocator.h
diff --git a/runtime/vm/flow_graph_allocator.h b/runtime/vm/flow_graph_allocator.h
index 34cca4575b458447355662d04ac72691ff46e61a..957fb3e4f9ea365217d5737740be8ace67c53d61 100644
--- a/runtime/vm/flow_graph_allocator.h
+++ b/runtime/vm/flow_graph_allocator.h
@@ -220,6 +220,13 @@ class FlowGraphAllocator : public ValueObject {
   // become free and can be reused for allocation.
   GrowableArray<intptr_t> spill_slots_;
 
+  // List of safepoints.
+  struct Safepoint {

[Vyacheslav Egorov (Google), 2012/08/13 12:54:46]

: public ValueObject ?

[Kevin Millikin (Google), 2012/08/13 15:10:37]

Nah.  The comment in that class indicates that ValueObject is not intended to be
passed by value.  :)

A minor issue is that it would no longer be POD (ValueObject has a user-defined
constructor) so I'd have to write a silly constructor here.

I think I'll probably introduce a SafepointInfo class that wraps this and hides
the bitmap builder as part of a future cleanup, anyway.

+    intptr_t position;
+    BitmapBuilder* stack_bitmap;
+  };
+  GrowableArray<Safepoint> safepoints_;
+
   bool blocked_cpu_regs_[kNumberOfCpuRegisters];
 
   DISALLOW_COPY_AND_ASSIGN(FlowGraphAllocator);
@@ -428,6 +435,8 @@ class LiveRange : public ZoneAllocated {
     return (Start() <= pos) && (pos < End());
   }
 
+  bool Covers(intptr_t pos) const;

[srdjan, 2012/08/10 23:11:05]

Could you add a brief comment differentiating between 'CanCover' and 'Covers'?

[Vyacheslav Egorov (Google), 2012/08/13 12:54:46]

I suggest renaming Covers to Contains to match naming of Contains in UseInterval
or maybe even AnySiblingContains()

Also please add comment as Srdjan suggested.

[Kevin Millikin (Google), 2012/08/13 15:10:37]

Done.

+
   Location spill_slot() const {
     return spill_slot_;
   }