X87: [builtins] Introduce proper base::ieee754::log.

src/crankshaft/x87/lithium-codegen-x87.cc

Index: src/crankshaft/x87/lithium-codegen-x87.cc
diff --git a/src/crankshaft/x87/lithium-codegen-x87.cc b/src/crankshaft/x87/lithium-codegen-x87.cc
index f75041f1a6799c9a139bb3c48acd522c9c265cb5..0f25b4b0ca3ac1b1e2a95c5f14e1d71f2cad3922 100644
--- a/src/crankshaft/x87/lithium-codegen-x87.cc
+++ b/src/crankshaft/x87/lithium-codegen-x87.cc
@@ -3679,40 +3679,17 @@ void LCodeGen::DoPower(LPower* instr) {
 
 void LCodeGen::DoMathLog(LMathLog* instr) {
   DCHECK(instr->value()->Equals(instr->result()));
+  X87Register result = ToX87Register(instr->result());
   X87Register input_reg = ToX87Register(instr->value());
   X87Fxch(input_reg);
 
-  Label positive, done, zero, nan_result;
-  __ fldz();
-  __ fld(1);
-  __ FCmp();
-  __ j(below, &nan_result, Label::kNear);
-  __ j(equal, &zero, Label::kNear);
-  // Positive input.
-  // {input, ln2}.
-  __ fldln2();
-  // {ln2, input}.
-  __ fxch();
-  // {result}.
-  __ fyl2x();
-  __ jmp(&done, Label::kNear);
-
-  __ bind(&nan_result);
-  X87PrepareToWrite(input_reg);
-  __ push(Immediate(0xffffffff));
-  __ push(Immediate(0x7fffffff));
-  __ fld_d(MemOperand(esp, 0));
-  __ lea(esp, Operand(esp, kDoubleSize));
-  X87CommitWrite(input_reg);
-  __ jmp(&done, Label::kNear);
-
-  __ bind(&zero);
-  ExternalReference ninf = ExternalReference::address_of_negative_infinity();
-  X87PrepareToWrite(input_reg);
-  __ fld_d(Operand::StaticVariable(ninf));
-  X87CommitWrite(input_reg);
-
-  __ bind(&done);
+  // Pass one double as argument on the stack.
+  __ PrepareCallCFunction(2, eax);
+  __ fstp_d(MemOperand(esp, 0));
+  X87PrepareToWrite(result);
+  __ CallCFunction(ExternalReference::ieee754_log_function(isolate()), 2);
+  // Return value is in st(0) on ia32.
+  X87CommitWrite(result);
 }