[builtins] Introduce proper Float64Atan and Float64Atan2 operators.

src/compiler/mips/code-generator-mips.cc

Index: src/compiler/mips/code-generator-mips.cc
diff --git a/src/compiler/mips/code-generator-mips.cc b/src/compiler/mips/code-generator-mips.cc
index 9401e20556bc927d858705f3b77fb9beab80096e..83b7081c8dbe63f487e3160b22f9f7dd850a95d7 100644
--- a/src/compiler/mips/code-generator-mips.cc
+++ b/src/compiler/mips/code-generator-mips.cc
@@ -485,6 +485,18 @@ FPUCondition FlagsConditionToConditionCmpFPU(bool& predicate,
     __ sync();                                           \
   } while (0)
 
+#define ASSEMBLE_IEEE754_BINOP(name)                                          \
+  do {                                                                        \
+    FrameScope scope(masm(), StackFrame::MANUAL);                             \
+    __ PrepareCallCFunction(0, 2, kScratchReg);                               \
+    __ MovToFloatParameters(i.InputDoubleRegister(0),                         \
+                            i.InputDoubleRegister(1));                        \
+    __ CallCFunction(ExternalReference::ieee754_##name##_function(isolate()), \
+                     0, 2);                                                   \
+    /* Move the result in the double result register. */                      \
+    __ MovFromFloatResult(i.OutputDoubleRegister());                          \
+  } while (0)
+
 #define ASSEMBLE_IEEE754_UNOP(name)                                           \
   do {                                                                        \
     FrameScope scope(masm(), StackFrame::MANUAL);                             \
@@ -729,6 +741,12 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
               Operand(offset.offset()));
       break;
     }
+    case kIeee754Float64Atan:
+      ASSEMBLE_IEEE754_UNOP(atan);
+      break;
+    case kIeee754Float64Atan2:
+      ASSEMBLE_IEEE754_BINOP(atan2);
+      break;
     case kIeee754Float64Log:
       ASSEMBLE_IEEE754_UNOP(log);
       break;