Remove n-ary select for now

Author: rossberg

interpreter/binary/decode.ml

@@ -259,7 +259,7 @@ let rec instr s =
 
   | 0x1a -> drop
   | 0x1b -> select None
-  | 0x1c -> select (Some (vec value_type s))
+  | 0x1c -> select (Some (value_type s))
 
   | 0x1d | 0x1e | 0x1f as b -> illegal s pos b
 

interpreter/binary/encode.ml

@@ -168,7 +168,7 @@ let encode m =
 
       | Drop -> op 0x1a
       | Select None -> op 0x1b
-      | Select (Some ts) -> op 0x1c; vec value_type ts
+      | Select (Some t) -> op 0x1c; value_type t
 
       | LocalGet x -> op 0x20; var x
       | LocalSet x -> op 0x21; var x

interpreter/syntax/ast.ml

@@ -71,7 +71,7 @@ and instr' =
   | Unreachable                       (* trap unconditionally *)
   | Nop                               (* do nothing *)
   | Drop                              (* forget a value *)
-  | Select of value_type list option  (* branchless conditional *)
+  | Select of value_type option       (* branchless conditional *)
   | Block of stack_type * instr list  (* execute in sequence *)
   | Loop of stack_type * instr list   (* loop header *)
   | If of stack_type * instr list * instr list  (* conditional *)

interpreter/text/arrange.ml

@@ -225,8 +225,7 @@ let rec instr e =
     | Nop -> "nop", []
     | Drop -> "drop", []
     | Select None -> "select", []
-    | Select (Some []) -> "select", [Node ("result", [])]
-    | Select (Some ts) -> "select", decls "result" ts
+    | Select (Some t) -> "select", decls "result" [t]
     | Block (ts, es) -> "block", stack_type ts @ list instr es
     | Loop (ts, es) -> "loop", stack_type ts @ list instr es
     | If (ts, es1, es2) ->

interpreter/text/parser.mly

@@ -348,26 +348,25 @@ plain_instr :
 
 select_instr :
   | SELECT select_instr_results
-    { let at = at () in fun c -> let b, ts = $2 in
-      select (if b then (Some ts) else None) @@ at }
+    { let at = at () in fun c -> select $2 @@ at }
 
 select_instr_results :
-  | LPAR RESULT value_type_list RPAR select_instr_results
-    { let _, ts = $5 in true, $3 @ ts }
+  | LPAR RESULT value_type RPAR
+    { Some $3 }
   | /* empty */
-    { false, [] }
+    { None }
 
 select_instr_instr :
   | SELECT select_instr_results_instr
     { let at1 = ati 1 in
-      fun c -> let b, ts, es = $2 c in
-      select (if b then (Some ts) else None) @@ at1, es }
+      fun c -> let t_opt, es = $2 c in
+      select t_opt @@ at1, es }
 
 select_instr_results_instr :
-  | LPAR RESULT value_type_list RPAR select_instr_results_instr
-    { fun c -> let _, ts, es = $5 c in true, $3 @ ts, es }
+  | LPAR RESULT value_type RPAR instr
+    { fun c -> Some $3, $5 c }
   | instr
-    { fun c -> false, [], $1 c }
+    { fun c -> None, $1 c }
 
 
 call_instr :
@@ -458,7 +457,7 @@ expr :  /* Sugar */
 expr1 :  /* Sugar */
   | plain_instr expr_list { fun c -> $2 c, $1 c }
   | SELECT select_expr_results
-    { fun c -> let b, ts, es = $2 c in es, select (if b then (Some ts) else None) }
+    { fun c -> let t_opt, es = $2 c in es, select t_opt }
   | CALL_INDIRECT var call_expr_type
     { fun c -> let x, es = $3 c in es, call_indirect ($2 c table) x }
   | CALL_INDIRECT call_expr_type  /* Sugar */
@@ -473,10 +472,10 @@ expr1 :  /* Sugar */
       let ts, (es, es1, es2) = $3 c c' in es, if_ ts es1 es2 }
 
 select_expr_results :
-  | LPAR RESULT value_type_list RPAR select_expr_results
-    { fun c -> let _, ts, es = $5 c in true, $3 @ ts, es }
+  | LPAR RESULT value_type RPAR expr_list
+    { fun c -> Some $3, $5 c }
   | expr_list
-    { fun c -> false, [], $1 c }
+    { fun c -> None, $1 c }
 
 call_expr_type :
   | type_use call_expr_params

interpreter/valid/valid.ml

@@ -185,10 +185,8 @@ let rec check_instr (c : context) (e : instr) (s : infer_stack_type) : op_type =
        " but stack has " ^ string_of_value_type t);
     [t; t; NumType I32Type] --> [t]
 
-  | Select (Some ts) ->
-    check_arity (List.length ts) e.at;
-    require (List.length ts <> 0) e.at "invalid result arity, 0 is not (yet) allowed";
-    (ts @ ts @ [NumType I32Type]) --> ts
+  | Select (Some t) ->
+    [t; t; NumType I32Type] --> [t]
 
   | Block (ts, es) ->
     check_arity (List.length ts) e.at;

test/core/select.wast

@@ -365,19 +365,22 @@
   (module (func $arity-0-implicit (select (nop) (nop) (i32.const 1))))
   "type mismatch"
 )
-(assert_invalid
-  (module (func $arity-0 (select (result) (nop) (nop) (i32.const 1))))
-  "invalid result arity"
+
+(assert_malformed
+  (module quote "(func $arity-0 (select (result) (nop) (nop) (i32.const 1)))")
+  "unexpected token"
 )
-(assert_invalid
-  (module (func $arity-2 (result i32 i32)
-    (select (result i32 i32)
-      (i32.const 0) (i32.const 0)
-      (i32.const 0) (i32.const 0)
-      (i32.const 1)
-    )
-  ))
-  "invalid result arity"
+(assert_malformed
+  (module quote
+    "(func $arity-2 (result i32 i32)"
+    "  (select (result i32 i32)"
+    "    (i32.const 0) (i32.const 0)"
+    "    (i32.const 0) (i32.const 0)"
+    "    (i32.const 1)"
+    "  )"
+    ")"
+  )
+  "unexpected token"
 )