Allow optimizing compiler to compute Math.log using untagged doubles.

src/ia32/lithium-codegen-ia32.cc

Index: src/ia32/lithium-codegen-ia32.cc
===================================================================
--- src/ia32/lithium-codegen-ia32.cc	(revision 5984)
+++ src/ia32/lithium-codegen-ia32.cc	(working copy)
@@ -2235,6 +2235,13 @@
 }
 
 
+void LCodeGen::DoMathLog(LUnaryMathOperation* instr) {
+  ASSERT(ToDoubleRegister(instr->result()).is(xmm1));
+  TranscendentalCacheSSE2Stub stub(TranscendentalCache::LOG);
+  CallCode(stub.GetCode(), RelocInfo::CODE_TARGET, instr);
+}
+
+
 void LCodeGen::DoUnaryMathOperation(LUnaryMathOperation* instr) {
   switch (instr->op()) {
     case kMathAbs:
@@ -2252,6 +2259,10 @@
     case kMathPowHalf:
       DoMathPowHalf(instr);
       break;
+    case kMathLog:
+      DoMathLog(instr);
+      break;
+
     default:
       UNREACHABLE();
   }