[regexp] Port RegExpExecStub to CSA (mostly)

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 c784edd7b54ca2fcacd04398b63c4cc801523f81..9978ec7e734668aed5b85cfc6053800d53c933bb 100644
--- a/src/x64/interface-descriptors-x64.cc
+++ b/src/x64/interface-descriptors-x64.cc
@@ -52,11 +52,15 @@ const Register ApiGetterDescriptor::CallbackRegister() { return rbx; }
 
 const Register MathPowTaggedDescriptor::exponent() { return rdx; }
 
-
 const Register MathPowIntegerDescriptor::exponent() {
   return MathPowTaggedDescriptor::exponent();
 }
 
+const Register RegExpExecDescriptor::StringRegister() { return arg_reg_1; }
+const Register RegExpExecDescriptor::LastIndexRegister() { return r11; }
+const Register RegExpExecDescriptor::StringStartRegister() { return arg_reg_3; }
+const Register RegExpExecDescriptor::StringEndRegister() { return arg_reg_4; }
+const Register RegExpExecDescriptor::CodeRegister() { return rax; }
 
 const Register GrowArrayElementsDescriptor::ObjectRegister() { return rax; }
 const Register GrowArrayElementsDescriptor::KeyRegister() { return rbx; }