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..679a0a409493936d22018074e8f9bbd0bcf6574f 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 +3879,14 @@ void LCodeGen::DoSmiUntag(LSmiUntag* instr) {
   if (instr->needs_check()) {
     __ test(ToRegister(input), Immediate(kSmiTagMask));
     DeoptimizeIf(not_zero, instr->environment());
+  } else {
+#if DEBUG

[Florian Schneider, 2012/06/12 09:01:13]

We usually use FLAG_debug_code to emit assertion in generated code so that the
generated code in debug and release mode is the same by default.

[danno, 2012/06/12 09:59:22]

Done.

+    Label ok;
+    __ test(ToRegister(input), Immediate(kSmiTagMask));
+    __ j(zero, &ok, Label::kNear);
+    __ int3();
+    __ bind(&ok);

[Florian Schneider, 2012/06/12 09:01:13]

You could replace this block of instructions with:

__ AbortIfNotSmi(ToRegister(input));

[danno, 2012/06/12 09:59:22]

Done.

+#endif
   }
   __ SmiUntag(ToRegister(input));
 }