Tweak Math.log on ia32/x64

src/x64/lithium-codegen-x64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
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 // modification, are permitted provided that the following conditions are
 // met:
 //
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@@ skipping 3655 matching lines @@
   XMMRegister result = ToDoubleRegister(instr->result());
   XMMRegister temp0 = double_scratch0();
   Register temp1 = ToRegister(instr->temp1());
   Register temp2 = ToRegister(instr->temp2());
 
   MathExpGenerator::EmitMathExp(masm(), input, result, temp0, temp1, temp2);
 }
 
 
 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);
 }
 
 
 void LCodeGen::DoMathTan(LMathTan* instr) {
   ASSERT(ToDoubleRegister(instr->result()).is(xmm1));
   TranscendentalCacheStub stub(TranscendentalCache::TAN,
                                TranscendentalCacheStub::UNTAGGED);
   CallCode(stub.GetCode(isolate()), RelocInfo::CODE_TARGET, instr);
 }
 
@@ skipping 1768 matching lines @@
                                FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64