Reapply r18377 it was reverted due to the unrelated bug it surfaced.

runtime/vm/intermediate_language_x64.cc

Index: runtime/vm/intermediate_language_x64.cc
diff --git a/runtime/vm/intermediate_language_x64.cc b/runtime/vm/intermediate_language_x64.cc
index c0e93f910b124bdca01eab2b8c476d4b550b0538..87aa256c99682a7a6fcf5863b2999f2636f3fa22 100644
--- a/runtime/vm/intermediate_language_x64.cc
+++ b/runtime/vm/intermediate_language_x64.cc
@@ -219,9 +219,7 @@ void AssertBooleanInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   Register obj = locs()->in(0).reg();
   Register result = locs()->out().reg();
 
-  if (!is_eliminated()) {
-    EmitAssertBoolean(obj, token_pos(), deopt_id(), locs(), compiler);
-  }
+  EmitAssertBoolean(obj, token_pos(), deopt_id(), locs(), compiler);
   ASSERT(obj == result);
 }
 
@@ -961,14 +959,16 @@ void StringFromCharCodeInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
 }
 
 
-intptr_t LoadIndexedInstr::ResultCid() const {
+CompileType* LoadIndexedInstr::ComputeInitialType() const {
   switch (class_id_) {
     case kArrayCid:
     case kImmutableArrayCid:
-      return kDynamicCid;
+      return CompileType::Dynamic();
+
     case kFloat32ArrayCid :
     case kFloat64ArrayCid :
-      return kDoubleCid;
+      return CompileType::FromCid(kDoubleCid);
+
     case kInt8ArrayCid:
     case kUint8ArrayCid:
     case kUint8ClampedArrayCid:
@@ -980,10 +980,11 @@ intptr_t LoadIndexedInstr::ResultCid() const {
     case kTwoByteStringCid:
     case kInt32ArrayCid:
     case kUint32ArrayCid:
-      return kSmiCid;
+      return CompileType::FromCid(kSmiCid);
+
     default:
       UNIMPLEMENTED();
-      return kSmiCid;
+      return NULL;
   }
 }
 
@@ -2127,8 +2128,8 @@ void BinarySmiOpInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
 
 
 LocationSummary* CheckEitherNonSmiInstr::MakeLocationSummary() const {
-  ASSERT((left()->ResultCid() != kDoubleCid) &&
-         (right()->ResultCid() != kDoubleCid));
+  ASSERT((left()->Type()->ToCid() != kDoubleCid) &&
+         (right()->Type()->ToCid() != kDoubleCid));
   const intptr_t kNumInputs = 2;
   const intptr_t kNumTemps = 1;
   LocationSummary* summary =
@@ -2225,7 +2226,7 @@ LocationSummary* UnboxDoubleInstr::MakeLocationSummary() const {
 
 
 void UnboxDoubleInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  const intptr_t value_cid = value()->ResultCid();
+  const intptr_t value_cid = value()->Type()->ToCid();
   const Register value = locs()->in(0).reg();
   const XmmRegister result = locs()->out().fpu_reg();
 
@@ -2627,8 +2628,6 @@ LocationSummary* CheckSmiInstr::MakeLocationSummary() const {
 
 
 void CheckSmiInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  // TODO(srdjan): Check if we can remove this by reordering CSE and LICM.
-  if (value()->ResultCid() == kSmiCid) return;
   Register value = locs()->in(0).reg();
   Label* deopt = compiler->AddDeoptStub(deopt_id(),
                                         kDeoptCheckSmi);