Avoid redundant smi check for Math.abs

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
===================================================================
--- src/x64/lithium-codegen-x64.cc	(revision 15942)
+++ src/x64/lithium-codegen-x64.cc	(working copy)
@@ -3457,7 +3457,7 @@
     __ xorps(scratch, scratch);
     __ subsd(scratch, input_reg);
     __ andpd(input_reg, scratch);
-  } else if (r.IsInteger32()) {
+  } else if (r.IsInteger32() || r.IsSmi()) {

[Jakob Kummerow, 2013/07/31 12:27:27]

This code is wrong. EmitIntegerMathAbs() uses testl/negl, which don't handle
Smis correctly. Repro case:

var a = [-1, -2];
function foo() {
  return Math.abs(a[0]);
}
print(foo());
print(foo());
%OptimizeFunctionOnNextCall(foo);
print(foo());

     EmitIntegerMathAbs(instr);
   } else {  // Tagged case.
     DeferredMathAbsTaggedHeapNumber* deferred =