[OCaml] Add OCaml APIs for Invoke arguments and destinations

[jberdine]

Summary

This patch adds OCaml APIs for LLVMGetNormalDest and LLVMGetUnwindDest
on InvokeInsts, as well as LLVMGetNumArgOperands on CallInsts and
InvokeInsts.

bindings/ocaml/llvm/llvm.ml

let add_call_site_attr f a i =
   llvm_add_call_site_attr f a (AttrIndex.to_int i)
 let call_site_attrs f i =
   llvm_call_site_attrs f (AttrIndex.to_int i)
 let remove_enum_call_site_attr f k i =
   llvm_remove_enum_call_site_attr f k (AttrIndex.to_int i)
 let remove_string_call_site_attr f k i =
   llvm_remove_string_call_site_attr f k (AttrIndex.to_int i)
 
-(*--... Operations on call instructions (only) .............................--*)
+(*--... Operations on call and invoke instructions (only) ..................--*)
+external num_arg_operands : llvalue -> int = "llvm_num_arg_operands"
 external is_tail_call : llvalue -> bool = "llvm_is_tail_call"
 external set_tail_call : bool -> llvalue -> unit = "llvm_set_tail_call"
+external get_normal_dest : llvalue -> llbasicblock = "LLVMGetNormalDest"
+external get_unwind_dest : llvalue -> llbasicblock = "LLVMGetUnwindDest"
 
 (*--... Operations on load/store instructions (only) .......................--*)
 external is_volatile : llvalue -> bool = "llvm_is_volatile"
 external set_volatile : bool -> llvalue -> unit = "llvm_set_volatile"
 
 (*--... Operations on terminators ..........................................--*)
 
 let is_terminator llv =

bindings/ocaml/llvm/llvm.mli

(** [remove_enum_call_site_attr f k i] removes enum attribute with kind [k]
     from the call instruction [ci] at position [i]. *)
 val remove_enum_call_site_attr : llvalue -> llattrkind -> AttrIndex.t -> unit
 
 (** [remove_string_call_site_attr f k i] removes string attribute with kind [k]
     from the call instruction [ci] at position [i]. *)
 val remove_string_call_site_attr : llvalue -> string -> AttrIndex.t -> unit
 
 
-(** {7 Operations on call instructions (only)} *)
+(** {7 Operations on call and invoke instructions (only)} *)
+
+(** [num_arg_operands ci] returns the number of arguments for the call or
+    invoke instruction [ci].  See the method
+    [llvm::CallInst::getNumArgOperands]. *)
+val num_arg_operands : llvalue -> int
 
 (** [is_tail_call ci] is [true] if the call instruction [ci] is flagged as
     eligible for tail call optimization, [false] otherwise.
     See the method [llvm::CallInst::isTailCall]. *)
 val is_tail_call : llvalue -> bool
 
 (** [set_tail_call tc ci] flags the call instruction [ci] as eligible for tail
     call optimization if [tc] is [true], clears otherwise.
     See the method [llvm::CallInst::setTailCall]. *)
 val set_tail_call : bool -> llvalue -> unit
 
+(** [get_normal_dest ii] is the normal destination basic block of an invoke
+    instruction. See the method [llvm::InvokeInst::getNormalDest()]. *)
+val get_normal_dest : llvalue -> llbasicblock
+
+(** [get_unwind_dest ii] is the unwind destination basic block of an invoke
+    instruction. See the method [llvm::InvokeInst::getUnwindDest()]. *)
+val get_unwind_dest : llvalue -> llbasicblock
+
 
 (** {7 Operations on load/store instructions (only)} *)
 
 (** [is_volatile i] is [true] if the load or store instruction [i] is marked
     as volatile.
     See the methods [llvm::LoadInst::isVolatile] and
     [llvm::StoreInst::isVolatile]. *)
 val is_volatile : llvalue -> bool

bindings/ocaml/llvm/llvm_ocaml.c

CAMLprim value llvm_remove_string_call_site_attr(LLVMValueRef F, value Kind,
                                                  value Index) {
   LLVMRemoveCallSiteStringAttribute(F, Int_val(Index), String_val(Kind),
                                     caml_string_length(Kind));
   return Val_unit;
 }
 
 /*--... Operations on call instructions (only) .............................--*/
 
+/* llvalue -> int */
+CAMLprim value llvm_num_arg_operands(LLVMValueRef V) {
+  return Val_int(LLVMGetNumArgOperands(V));
+}
+
 /* llvalue -> bool */
 CAMLprim value llvm_is_tail_call(LLVMValueRef CallInst) {
   return Val_bool(LLVMIsTailCall(CallInst));
 }
 
 /* bool -> llvalue -> unit */
 CAMLprim value llvm_set_tail_call(value IsTailCall,
                                   LLVMValueRef CallInst) {