Generalize bounds checks.

runtime/vm/intermediate_language_ia32.cc

Index: runtime/vm/intermediate_language_ia32.cc
diff --git a/runtime/vm/intermediate_language_ia32.cc b/runtime/vm/intermediate_language_ia32.cc
index 2ef1531bc842296701f6e0eee04ed36f91fd1819..7fb14b7dfb795d88cb5af6de408c4a9290c168b6 100644
--- a/runtime/vm/intermediate_language_ia32.cc
+++ b/runtime/vm/intermediate_language_ia32.cc
@@ -5463,10 +5463,10 @@ LocationSummary* CheckClassInstr::MakeLocationSummary(Isolate* isolate,
 
 
 void CheckClassInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  const ICData::DeoptReasonId deopt_reason = licm_hoisted_ ?
-      ICData::kDeoptHoistedCheckClass : ICData::kDeoptCheckClass;
+  Label* deopt = compiler->AddDeoptStub(deopt_id(),
+                                        ICData::kDeoptCheckClass,
+                                        licm_hoisted_ ? ICData::kHoisted : 0);
   if (IsNullCheck()) {
-    Label* deopt = compiler->AddDeoptStub(deopt_id(), deopt_reason);
     const Immediate& raw_null =
         Immediate(reinterpret_cast<intptr_t>(Object::null()));
     __ cmpl(locs()->in(0).reg(), raw_null);
@@ -5478,7 +5478,6 @@ void CheckClassInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
          (unary_checks().NumberOfChecks() > 1));
   Register value = locs()->in(0).reg();
   Register temp = locs()->temp(0).reg();
-  Label* deopt = compiler->AddDeoptStub(deopt_id(), deopt_reason);
   Label is_ok;
   intptr_t cix = 0;
   if (unary_checks().GetReceiverClassIdAt(cix) == kSmiCid) {
@@ -5584,8 +5583,10 @@ LocationSummary* CheckArrayBoundInstr::MakeLocationSummary(Isolate* isolate,
 
 
 void CheckArrayBoundInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  Label* deopt = compiler->AddDeoptStub(deopt_id(),
-                                        ICData::kDeoptCheckArrayBound);
+  Label* deopt = compiler->AddDeoptStub(
+      deopt_id(),
+      ICData::kDeoptCheckArrayBound,
+      generalized_ ? ICData::kGeneralized : 0);
 
   Location length_loc = locs()->in(kLengthPos);
   Location index_loc = locs()->in(kIndexPos);
@@ -5603,8 +5604,13 @@ void CheckArrayBoundInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   if (length_loc.IsConstant()) {
     Register index = index_loc.reg();
     const Smi& length = Smi::Cast(length_loc.constant());
-    __ cmpl(index, Immediate(reinterpret_cast<int32_t>(length.raw())));
-    __ j(ABOVE_EQUAL, deopt);
+    if (length.Value() == Smi::kMaxValue) {
+      __ testl(index, index);
+      __ j(NEGATIVE, deopt);
+    } else {
+      __ cmpl(index, Immediate(reinterpret_cast<int32_t>(length.raw())));
+      __ j(ABOVE_EQUAL, deopt);
+    }

[regis, 2014/12/17 22:00:39]

Slava,

I stumbled upon this code and do not quite understand how it can be correct. If
both index and length are Smi::kMaxValue (highly improbable, but still), then we
will emit a test instruction instead of the compare. We will not deopt, because
index is not negative, but we should.

What am I missing?

Thanks,
Regis

   } else if (index_loc.IsConstant()) {
     const Smi& index = Smi::Cast(index_loc.constant());
     if (length_loc.IsStackSlot()) {