[builtins] Introduce proper Float64Atan and Float64Atan2 operators.

src/assembler.cc

Index: src/assembler.cc
diff --git a/src/assembler.cc b/src/assembler.cc
index 8fe196cabb1b488e03cac430231879e5e447d12e..03859b5cb4c33ec39334bf534390c216ca54b2cd 100644
--- a/src/assembler.cc
+++ b/src/assembler.cc
@@ -1323,7 +1323,7 @@ ExternalReference ExternalReference::f64_asin_wrapper_function(
 }
 
 static void f64_atan_wrapper(double* param) {
-  WriteDoubleValue(param, std::atan(ReadDoubleValue(param)));
+  WriteDoubleValue(param, base::ieee754::atan(ReadDoubleValue(param)));
 }
 
 ExternalReference ExternalReference::f64_atan_wrapper_function(
@@ -1392,7 +1392,7 @@ static void f64_atan2_wrapper(double* param0, double* param1) {
     if (y < 0) multiplier *= 3;
     WriteDoubleValue(param0, multiplier * kPiDividedBy4);
   } else {
-    WriteDoubleValue(param0, std::atan2(x, y));
+    WriteDoubleValue(param0, base::ieee754::atan2(x, y));
   }
 }
 
@@ -1648,6 +1648,16 @@ ExternalReference ExternalReference::address_of_regexp_stack_memory_size(
 
 #endif  // V8_INTERPRETED_REGEXP
 
+ExternalReference ExternalReference::ieee754_atan_function(Isolate* isolate) {
+  return ExternalReference(
+      Redirect(isolate, FUNCTION_ADDR(base::ieee754::atan), BUILTIN_FP_CALL));
+}
+
+ExternalReference ExternalReference::ieee754_atan2_function(Isolate* isolate) {
+  return ExternalReference(Redirect(
+      isolate, FUNCTION_ADDR(base::ieee754::atan2), BUILTIN_FP_FP_CALL));
+}
+
 ExternalReference ExternalReference::ieee754_log_function(Isolate* isolate) {
   return ExternalReference(
       Redirect(isolate, FUNCTION_ADDR(base::ieee754::log), BUILTIN_FP_CALL));