Eliminate redundant smi checks

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 edcd8fc4da276ba0600e485540c4e3052fdf9319..4c8b963df98ca1f899a9ad6f9caf51f10b591f57 100644
--- a/src/ia32/lithium-codegen-ia32.cc
+++ b/src/ia32/lithium-codegen-ia32.cc
@@ -2435,8 +2435,13 @@ void LCodeGen::DoLoadKeyedFastElement(LLoadKeyedFastElement* instr) {
 
   // Check for the hole value.
   if (instr->hydrogen()->RequiresHoleCheck()) {
-    __ cmp(result, factory()->the_hole_value());
-    DeoptimizeIf(equal, instr->environment());
+    if (IsFastSmiElementsKind(instr->hydrogen()->elements_kind())) {
+      __ test(result, Immediate(kSmiTagMask));
+      DeoptimizeIf(not_equal, instr->environment());
+    } else {
+      __ cmp(result, factory()->the_hole_value());
+      DeoptimizeIf(equal, instr->environment());
+    }
   }
 }
 
@@ -3874,6 +3879,10 @@ void LCodeGen::DoSmiUntag(LSmiUntag* instr) {
   if (instr->needs_check()) {
     __ test(ToRegister(input), Immediate(kSmiTagMask));
     DeoptimizeIf(not_zero, instr->environment());
+  } else {
+    if (FLAG_debug_code) {
+      __ AbortIfNotSmi(ToRegister(input));
+    }
   }
   __ SmiUntag(ToRegister(input));
 }