[builtins] Sanitize the machinery around Construct calls.

src/x64/interface-descriptors-x64.cc

Index: src/x64/interface-descriptors-x64.cc
diff --git a/src/x64/interface-descriptors-x64.cc b/src/x64/interface-descriptors-x64.cc
index 0b17b162fb076afbce541ceaad80c18d238bf341..ba4a909ebd0e3b267d33fd5b6cd519abcefd6b85 100644
--- a/src/x64/interface-descriptors-x64.cc
+++ b/src/x64/interface-descriptors-x64.cc
@@ -186,12 +186,11 @@ void CallConstructDescriptor::InitializePlatformSpecific(
     CallInterfaceDescriptorData* data) {
   // rax : number of arguments
   // rbx : feedback vector
-  // rcx : new target (for IsSuperConstructorCall)
   // rdx : slot in feedback vector (Smi, for RecordCallTarget)
   // rdi : constructor function
   // TODO(turbofan): So far we don't gather type feedback and hence skip the
   // slot parameter, but ArrayConstructStub needs the vector to be undefined.
-  Register registers[] = {rax, rdi, rcx, rbx};
+  Register registers[] = {rax, rdi, rbx};
   data->InitializePlatformSpecific(arraysize(registers), registers);
 }
 
@@ -205,6 +204,16 @@ void CallTrampolineDescriptor::InitializePlatformSpecific(
 }
 
 
+void ConstructTrampolineDescriptor::InitializePlatformSpecific(
+    CallInterfaceDescriptorData* data) {
+  // rax : number of arguments
+  // rdx : the new target
+  // rdi : the target to call
+  Register registers[] = {rdi, rdx, rax};
+  data->InitializePlatformSpecific(arraysize(registers), registers);
+}
+
+
 void RegExpConstructResultDescriptor::InitializePlatformSpecific(
     CallInterfaceDescriptorData* data) {
   Register registers[] = {rcx, rbx, rax};