Collect type feedback for fields.

runtime/vm/intermediate_language.cc

Index: runtime/vm/intermediate_language.cc
diff --git a/runtime/vm/intermediate_language.cc b/runtime/vm/intermediate_language.cc
index 40300289f755dd02f357971572cb69af70d9e761..0e7b76db41c6256ab938893f9ac1f818527a47f4 100644
--- a/runtime/vm/intermediate_language.cc
+++ b/runtime/vm/intermediate_language.cc
@@ -69,7 +69,8 @@ bool Value::Equals(Value* other) const {
 CheckClassInstr::CheckClassInstr(Value* value,
                                  intptr_t deopt_id,
                                  const ICData& unary_checks)
-    : unary_checks_(unary_checks) {
+    : unary_checks_(unary_checks),
+      null_check_(false) {
   ASSERT(unary_checks.IsZoneHandle());
   // Expected useful check data.
   ASSERT(!unary_checks_.IsNull());
@@ -109,6 +110,16 @@ bool CheckClassInstr::AffectedBySideEffect() const {
 }
 
 
+bool GuardFieldInstr::AttributesEqual(Instruction* other) const {
+  return field().raw() == other->AsGuardField()->field().raw();
+}
+
+
+bool GuardFieldInstr::AffectedBySideEffect() const {
+  return false;
+}
+
+
 bool CheckArrayBoundInstr::AttributesEqual(Instruction* other) const {
   CheckArrayBoundInstr* other_check = other->AsCheckArrayBound();
   ASSERT(other_check != NULL);
@@ -1308,6 +1319,26 @@ Instruction* CheckClassInstr::Canonicalize(FlowGraphOptimizer* optimizer) {
 }
 
 
+Instruction* GuardFieldInstr::Canonicalize(FlowGraphOptimizer* optimizer) {
+  if (field().guarded_cid() == kDynamicCid) {
+    return NULL;  // Nothing to guard.
+  }
+
+  if (field().is_nullable() && value()->Type()->IsNull()) {
+    return NULL;
+  }
+
+  const intptr_t cid = field().is_nullable() ? value()->Type()->ToNullableCid()
+                                             : value()->Type()->ToCid();
+  if (field().guarded_cid() == cid) {
+    return NULL;  // Value is guaranteed to have this cid.
+  }
+
+
+  return this;
+}
+
+
 Instruction* CheckSmiInstr::Canonicalize(FlowGraphOptimizer* optimizer) {
   return (value()->Type()->ToCid() == kSmiCid) ?  NULL : this;
 }