MIPS: Eliminate redundant smi checks

src/mips/lithium-codegen-mips.cc

Index: src/mips/lithium-codegen-mips.cc
diff --git a/src/mips/lithium-codegen-mips.cc b/src/mips/lithium-codegen-mips.cc
index 2073d04d9e924e7400e3987ae78f37b9043b1295..932f6aaef662393f20c6b27ef86944e4c23dbffd 100644
--- a/src/mips/lithium-codegen-mips.cc
+++ b/src/mips/lithium-codegen-mips.cc
@@ -2510,8 +2510,13 @@ void LCodeGen::DoLoadKeyedFastElement(LLoadKeyedFastElement* instr) {
 
   // Check for the hole value.
   if (instr->hydrogen()->RequiresHoleCheck()) {
-    __ LoadRoot(scratch, Heap::kTheHoleValueRootIndex);
-    DeoptimizeIf(eq, instr->environment(), result, Operand(scratch));
+    if (IsFastSmiElementsKind(instr->hydrogen()->elements_kind())) {
+      __ And(scratch, result, Operand(kSmiTagMask));
+      DeoptimizeIf(ne, instr->environment(), scratch, Operand(zero_reg));
+    } else {
+      __ LoadRoot(scratch, Heap::kTheHoleValueRootIndex);
+      DeoptimizeIf(eq, instr->environment(), result, Operand(scratch));
+    }
   }
 }