Generalize bounds checks.

runtime/vm/intermediate_language_ia32.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_IA32.
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/dart_entry.h"
@@ skipping 5445 matching lines @@
     summary->set_temp(0, Location::RequiresRegister());
     if (need_mask_temp) {
       summary->set_temp(1, Location::RequiresRegister());
     }
   }
   return summary;
 }
 
 
 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);
     __ j(EQUAL, deopt);
     return;
   }
 
   ASSERT((unary_checks().GetReceiverClassIdAt(0) != kSmiCid) ||
          (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) {
     __ testl(value, Immediate(kSmiTagMask));
     __ j(ZERO, &is_ok);
     cix++;  // Skip first check.
   } else {
     __ testl(value, Immediate(kSmiTagMask));
     __ j(ZERO, deopt);
   }
@@ skipping 85 matching lines @@
     locs->set_in(kLengthPos, Location::RegisterOrSmiConstant(length()));
   } else {
     locs->set_in(kLengthPos, Location::PrefersRegister());
   }
   locs->set_in(kIndexPos, Location::RegisterOrSmiConstant(index()));
   return locs;
 }
 
 
 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);
 
   if (length_loc.IsConstant() && index_loc.IsConstant()) {
     ASSERT((Smi::Cast(length_loc.constant()).Value() <=
             Smi::Cast(index_loc.constant()).Value()) ||
            (Smi::Cast(index_loc.constant()).Value() < 0));
     // Unconditionally deoptimize for constant bounds checks because they
     // only occur only when index is out-of-bounds.
     __ jmp(deopt);
     return;
   }
 
   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()) {
       const Address& length = length_loc.ToStackSlotAddress();
       __ cmpl(length, Immediate(reinterpret_cast<int32_t>(index.raw())));
     } else {
       Register length = length_loc.reg();
       __ cmpl(length, Immediate(reinterpret_cast<int32_t>(index.raw())));
     }
     __ j(BELOW_EQUAL, deopt);
@@ skipping 1153 matching lines @@
   __ movl(EDX, Immediate(kInvalidObjectPointer));
   __ movl(EDX, Immediate(kInvalidObjectPointer));
 #endif
 }
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_IA32