Fix Smi::IsValid assert in StringCharCodeAt deferred code.

src/ia32/lithium-codegen-ia32.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
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 // modification, are permitted provided that the following conditions are
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 //
 //     * Redistributions of source code must retain the above copyright
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@@ skipping 2732 matching lines @@
   Register string = ToRegister(instr->string());
   Register result = ToRegister(instr->result());
 
   // TODO(3095996): Get rid of this. For now, we need to make the
   // result register contain a valid pointer because it is already
   // contained in the register pointer map.
   __ Set(result, Immediate(0));
 
   __ PushSafepointRegisters();
   __ push(string);
-  // Push the index as a smi.
+  // Push the index as a smi. It's safe because this instruction must
+  // be dominated by a bounds check and because of the assert.
+  STATIC_ASSERT(String::kMaxLength <= Smi::kMaxValue);
   if (instr->index()->IsConstantOperand()) {
     int const_index = ToInteger32(LConstantOperand::cast(instr->index()));
+    if (!Smi::IsValid(const_index)) {

[Mads Ager (chromium), 2011/01/20 15:03:17]

We shouldn't generate code at all for this instruction in this case. Can we just
do an unconditional deoptimization and return? Or catch this at a higher level
and never build this graph?

+      // Guaranteed to be out of bounds, so we can use "-1" to have a
+      // valid smi.
+      const_index = -1;
+    }
     __ push(Immediate(Smi::FromInt(const_index)));
   } else {
     Register index = ToRegister(instr->index());
     __ SmiTag(index);
     __ push(index);
   }
   __ CallRuntimeSaveDoubles(Runtime::kStringCharCodeAt);
   RecordSafepointWithRegisters(
       instr->pointer_map(), 2, Safepoint::kNoDeoptimizationIndex);
   if (FLAG_debug_code) {
@@ skipping 817 matching lines @@
   ASSERT(osr_pc_offset_ == -1);
   osr_pc_offset_ = masm()->pc_offset();
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32