Fix an undetected Smi overflow on ARM.

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 2901 matching lines @@
   Register result = locs()->out(0).reg();
   ASSERT(left == result);
   Label* deopt = NULL;
   if (CanDeoptimize()) {
     deopt  = compiler->AddDeoptStub(deopt_id(), ICData::kDeoptBinarySmiOp);
   }
 
   if (locs()->in(1).IsConstant()) {
     const Object& constant = locs()->in(1).constant();
     ASSERT(constant.IsSmi());
-    const int32_t imm =
-        reinterpret_cast<int32_t>(constant.raw());
+    const int32_t imm = reinterpret_cast<int32_t>(constant.raw());
     switch (op_kind()) {
-      case Token::kADD:
-        __ addl(left, Immediate(imm));
-        if (deopt != NULL) __ j(OVERFLOW, deopt);
+    case Token::kADD:
+        if (imm != 0) {
+          // Checking overflow without emitting an instruction would be wrong.
+          __ addl(left, Immediate(imm));
+          if (deopt != NULL) __ j(OVERFLOW, deopt);
+        }
         break;
       case Token::kSUB: {
-        __ subl(left, Immediate(imm));
-        if (deopt != NULL) __ j(OVERFLOW, deopt);
+        if (imm != 0) {
+          // Checking overflow without emitting an instruction would be wrong.
+          __ subl(left, Immediate(imm));
+          if (deopt != NULL) __ j(OVERFLOW, deopt);
+        }
         break;
       }
       case Token::kMUL: {
         // Keep left value tagged and untag right value.
         const intptr_t value = Smi::Cast(constant).Value();
         if (value == 2) {
           __ shll(left, Immediate(1));
         } else {
           __ imull(left, Immediate(value));
         }
@@ skipping 3048 matching lines @@
     }
   }
 
   __ setcc(true_condition, DL);
 
   if (is_power_of_two_kind) {
     const intptr_t shift =
         Utils::ShiftForPowerOfTwo(Utils::Maximum(true_value, false_value));
     __ shll(EDX, Immediate(shift + kSmiTagSize));
   } else {
-    __ subl(EDX, Immediate(1));
+    __ decl(EDX);
     __ andl(EDX, Immediate(
         Smi::RawValue(true_value) - Smi::RawValue(false_value)));
     if (false_value != 0) {
       __ addl(EDX, Immediate(Smi::RawValue(false_value)));
     }
   }
 }
 
 
 LocationSummary* ClosureCallInstr::MakeLocationSummary(bool opt) const {
@@ skipping 79 matching lines @@
                          PcDescriptors::kOther,
                          locs());
   __ Drop(ArgumentCount());  // Discard arguments.
 }
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_IA32