[builtins] Introduce proper Float64Log1p operator.

src/compiler/machine-operator-reducer.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/machine-operator-reducer.h"
 
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
 #include "src/base/ieee754.h"
 #include "src/codegen.h"
@@ skipping 370 matching lines @@
       if (m.IsFoldable()) {  // K % K => K
         return ReplaceFloat64(modulo(m.left().Value(), m.right().Value()));
       }
       break;
     }
     case IrOpcode::kFloat64Log: {
       Float64Matcher m(node->InputAt(0));
       if (m.HasValue()) return ReplaceFloat64(base::ieee754::log(m.Value()));
       break;
     }
+    case IrOpcode::kFloat64Log1p: {
+      Float64Matcher m(node->InputAt(0));
+      if (m.HasValue()) return ReplaceFloat64(base::ieee754::log1p(m.Value()));
+      break;
+    }
     case IrOpcode::kChangeFloat32ToFloat64: {
       Float32Matcher m(node->InputAt(0));
       if (m.HasValue()) return ReplaceFloat64(m.Value());
       break;
     }
     case IrOpcode::kChangeFloat64ToInt32: {
       Float64Matcher m(node->InputAt(0));
       if (m.HasValue()) return ReplaceInt32(FastD2I(m.Value()));
       if (m.IsChangeInt32ToFloat64()) return Replace(m.node()->InputAt(0));
       break;
@@ skipping 677 matching lines @@
 MachineOperatorBuilder* MachineOperatorReducer::machine() const {
   return jsgraph()->machine();
 }
 
 
 Graph* MachineOperatorReducer::graph() const { return jsgraph()->graph(); }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8