Tweak Math.log on ia32/x64

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 6fe64c553ec39222eb7741696892cc436b5d5799..c9bccf54136caeb320da3c41a9b8ed00da539b89 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -3673,10 +3673,35 @@ void LCodeGen::DoMathExp(LMathExp* instr) {
 
 
 void LCodeGen::DoMathLog(LMathLog* instr) {
-  ASSERT(ToDoubleRegister(instr->result()).is(xmm1));
-  TranscendentalCacheStub stub(TranscendentalCache::LOG,
-                               TranscendentalCacheStub::UNTAGGED);
-  CallCode(stub.GetCode(isolate()), RelocInfo::CODE_TARGET, instr);
+  ASSERT(instr->value()->Equals(instr->result()));
+  XMMRegister input_reg = ToDoubleRegister(instr->value());
+  XMMRegister xmm_scratch = double_scratch0();
+  Label positive, done, zero;
+  __ xorps(xmm_scratch, xmm_scratch);
+  __ ucomisd(input_reg, xmm_scratch);
+  __ j(above, &positive, Label::kNear);
+  __ j(equal, &zero, Label::kNear);
+  ExternalReference nan =
+      ExternalReference::address_of_canonical_non_hole_nan();
+  Operand nan_operand = __ ExternalOperand(nan);

[Jakob Kummerow, 2013/10/17 12:49:29]

nit: please use "masm->" instead of "__" here. "__" is for emitting
instructions. I think I'd also inline nan_operand directly:

  __ movsd(input_reg, masm->ExternalOperand(nan));

[Weiliang, 2013/10/17 13:19:36]

Done.

+  __ movsd(input_reg, nan_operand);
+  __ jmp(&done, Label::kNear);
+  __ bind(&zero);
+  ExternalReference ninf =
+      ExternalReference::address_of_negative_infinity();
+  Operand ninf_operand = __ ExternalOperand(ninf);

[Jakob Kummerow, 2013/10/17 12:49:29]

same here

[Weiliang, 2013/10/17 13:19:36]

Done.

+  __ movsd(input_reg, ninf_operand);
+  __ jmp(&done, Label::kNear);
+  __ bind(&positive);
+  __ fldln2();
+  __ subq(rsp, Immediate(kDoubleSize));
+  __ movsd(Operand(rsp, 0), input_reg);
+  __ fld_d(Operand(rsp, 0));
+  __ fyl2x();
+  __ fstp_d(Operand(rsp, 0));
+  __ movsd(input_reg, Operand(rsp, 0));
+  __ addq(rsp, Immediate(kDoubleSize));
+  __ bind(&done);
 }