Fix Smi::IsValid assert in StringCharCodeAt deferred code.

src/ia32/lithium-codegen-ia32.cc

Index: src/ia32/lithium-codegen-ia32.cc
diff --git a/src/ia32/lithium-codegen-ia32.cc b/src/ia32/lithium-codegen-ia32.cc
index 0fc3f2541b57525d1406372b82a427c10276a623..1a3a1f796283130597be024e5735d17c85857313 100644
--- a/src/ia32/lithium-codegen-ia32.cc
+++ b/src/ia32/lithium-codegen-ia32.cc
@@ -2750,9 +2750,16 @@ void LCodeGen::DoDeferredStringCharCodeAt(LStringCharCodeAt* instr) {
 
   __ 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());