Basic support for tracking smi-only arrays on ia32.

src/ia32/ic-ia32.cc

 // Copyright 2011 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 792 matching lines @@
   // address to store into and fall through to fast case.
   __ cmp(ecx, FieldOperand(edx, JSArray::kLengthOffset));  // Compare smis.
   __ j(above_equal, &extra);
 
   // Fast case: Do the store.
   __ bind(&fast);
   // eax: value
   // ecx: key (a smi)
   // edx: receiver
   // edi: FixedArray receiver->elements
+
+  if (FLAG_smi_only_arrays) {
+    Label not_smi_only;
+    // Make sure the elements are smi-only.
+    __ mov(ebx, FieldOperand(edx, HeapObject::kMapOffset));
+    __ CheckFastSmiOnlyElements(ebx, &not_smi_only, Label::kNear);
+    // Non-smis need to call into the runtime if the array is smi only.
+    __ JumpIfNotSmi(eax, &slow);
+    __ mov(CodeGenerator::FixedArrayElementOperand(edi, ecx), eax);
+    __ ret(0);
+    __ bind(&not_smi_only);
+  }
+
   __ mov(CodeGenerator::FixedArrayElementOperand(edi, ecx), eax);
 
   // Update write barrier for the elements array address.
   __ mov(edx, Operand(eax));  // Preserve the value which is returned.
   __ RecordWriteArray(edi, edx, ecx, kDontSaveFPRegs);
   __ ret(0);
 }
 
 
 // The generated code does not accept smi keys.
@@ skipping 814 matching lines @@
   Condition cc = *jmp_address == Assembler::kJncShortOpcode
       ? not_zero
       : zero;
   *jmp_address = static_cast<byte>(Assembler::kJccShortPrefix | cc);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32