Make sure that top bits are zero when storing untagged 32 bit values

src/x64/lithium-codegen-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3214 matching lines @@
       case DICTIONARY_ELEMENTS:
       case NON_STRICT_ARGUMENTS_ELEMENTS:
         UNREACHABLE();
         break;
     }
   }
 }
 
 
 void LCodeGen::DoBoundsCheck(LBoundsCheck* instr) {
-  if (instr->index()->IsConstantOperand()) {
-    if (instr->length()->IsRegister()) {
-      __ cmpq(ToRegister(instr->length()),
+  if (instr->length()->IsRegister()) {
+    Register reg = ToRegister(instr->length());
+    if (FLAG_debug_code) {
+      __ AbortIfNotZeroExtended(reg);
+    }
+    if (instr->index()->IsConstantOperand()) {
+      __ cmpq(reg,
               Immediate(ToInteger32(LConstantOperand::cast(instr->index()))));
     } else {
+      Register reg2 = ToRegister(instr->index());
+      if (FLAG_debug_code) {
+        __ AbortIfNotZeroExtended(reg2);
+      }
+      __ cmpq(reg, reg2);
+    }
+  } else {
+    if (instr->index()->IsConstantOperand()) {
       __ cmpq(ToOperand(instr->length()),
               Immediate(ToInteger32(LConstantOperand::cast(instr->index()))));
-    }
-  } else {
-    if (instr->length()->IsRegister()) {
-      __ cmpq(ToRegister(instr->length()), ToRegister(instr->index()));
     } else {
       __ cmpq(ToOperand(instr->length()), ToRegister(instr->index()));
     }
   }
   DeoptimizeIf(below_equal, instr->environment());
 }
 
 
 void LCodeGen::DoStoreKeyedFastElement(LStoreKeyedFastElement* instr) {
   Register value = ToRegister(instr->value());
@@ skipping 1148 matching lines @@
   RegisterEnvironmentForDeoptimization(environment, Safepoint::kNoLazyDeopt);
   ASSERT(osr_pc_offset_ == -1);
   osr_pc_offset_ = masm()->pc_offset();
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64