Support reusable boxes for Float32x4 fields

runtime/vm/flow_graph_compiler_ia32.cc

Index: runtime/vm/flow_graph_compiler_ia32.cc
diff --git a/runtime/vm/flow_graph_compiler_ia32.cc b/runtime/vm/flow_graph_compiler_ia32.cc
index 4b7d0d2c7cd41497de9d83944bf74c916a8d502b..e4d7b9f9b9e180228cd690ac81d2e725c555c842 100644
--- a/runtime/vm/flow_graph_compiler_ia32.cc
+++ b/runtime/vm/flow_graph_compiler_ia32.cc
@@ -28,6 +28,7 @@ DECLARE_FLAG(int, reoptimization_counter_threshold);
 DECLARE_FLAG(bool, enable_type_checks);
 DECLARE_FLAG(bool, eliminate_type_checks);
 DECLARE_FLAG(bool, throw_on_javascript_int_overflow);
+DECLARE_FLAG(bool, enable_simd_inline);
 
 
 FlowGraphCompiler::~FlowGraphCompiler() {
@@ -46,6 +47,11 @@ bool FlowGraphCompiler::SupportsUnboxedMints() {
 }
 
 
+bool FlowGraphCompiler::SupportsUnboxedFloat32x4() {
+  return FLAG_enable_simd_inline;
+}
+
+
 bool FlowGraphCompiler::SupportsSinCos() {
   return true;
 }