Put live register bits in stackmaps.

runtime/vm/flow_graph_compiler.cc

Index: runtime/vm/flow_graph_compiler.cc
diff --git a/runtime/vm/flow_graph_compiler.cc b/runtime/vm/flow_graph_compiler.cc
index 264b623ade62d524a66d1fd3562d0a00c9cc2d39..dd03a01ab3582295651d5797f94113efdc9cda1a 100644
--- a/runtime/vm/flow_graph_compiler.cc
+++ b/runtime/vm/flow_graph_compiler.cc
@@ -237,8 +237,24 @@ void FlowGraphCompiler::RecordSafepoint(LocationSummary* locs) {
   if (is_optimizing()) {
     BitmapBuilder* bitmap = locs->stack_bitmap();
     ASSERT(bitmap != NULL);
+    ASSERT(bitmap->Length() <= StackSize());
+    // Pad the bitmap out to describe all the spill slots.
     bitmap->SetLength(StackSize());
-    stackmap_table_builder_->AddEntry(assembler()->CodeSize(), bitmap);
+
+    // Slow path code can have registers at the safepoint.
+    if (!locs->always_calls()) {
+      for (intptr_t i = 0; i < kNumberOfCpuRegisters; ++i) {

[Vyacheslav Egorov (Google), 2012/08/27 14:54:51]

This is tightly couple with the way we push registers. Consider adding a comment
for that.

[Kevin Millikin (Google), 2012/08/29 12:40:41]

Done.

+        Register reg = static_cast<Register>(i);
+        if (locs->live_registers()->ContainsRegister(reg)) {
+          bitmap->Set(bitmap->Length(), true);
+        }
+      }

[Vyacheslav Egorov (Google), 2012/08/27 14:54:51]

Also please handle XMMRegisters here and remove a hack used for this currently.
This will be a good test.

+    }
+
+    intptr_t register_count = bitmap->Length() - StackSize();
+    stackmap_table_builder_->AddEntry(assembler()->CodeSize(),
+                                      bitmap,
+                                      register_count);
   }
 }