Effects: use global flow analysis to detect more exact calls

ocsigen · Jan 25, 2023 · d773062 · d773062
1 parent dde36fe
commit d773062
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Showing 2 changed files with 15 additions and 7 deletions.
diff --git a/compiler/lib/effects.ml b/compiler/lib/effects.ml
@@ -240,6 +240,7 @@ type st =
   ; matching_exn_handler : (Addr.t, Addr.t) Hashtbl.t
   ; block_order : (Addr.t, int) Hashtbl.t
   ; live_vars : Deadcode.variable_uses
+  ; flow_info : Global_flow.info
   ; cps_calls : cps_calls ref
   }
 
@@ -361,6 +362,7 @@ let cps_instr ~st (instr : instr) : instr =
   | Let (x, Apply { f; args; _ }) when not (Var.Set.mem x st.cps_needed) ->
       (* At the moment, we turn into CPS any function not called with
          the right number of parameter *)
+      assert (Global_flow.exact_call st.flow_info f (List.length args));
       Let (x, Apply { f; args; exact = true })
   | Let (_, (Apply _ | Prim (Extern ("%resume" | "%perform" | "%reperform"), _))) ->
       assert false
@@ -412,15 +414,20 @@ let cps_block ~st ~k pc block =
     in
     match e with
     | Apply { f; args; exact } when Var.Set.mem x st.cps_needed ->
-        Some (fun ~k -> tail_call ~st ~exact ~check:true ~f (args @ [ k ]))
+        Some
+          (fun ~k ->
+            let exact =
+              exact || Global_flow.exact_call st.flow_info f (List.length args)
+            in
+            tail_call ~st ~exact ~check:true ~f (args @ [ k ]))
     | Prim (Extern "%resume", [ Pv stack; Pv f; Pv arg ]) ->
         Some
           (fun ~k ->
             let k' = Var.fresh_n "cont" in
             tail_call
               ~st
               ~instrs:[ Let (k', Prim (Extern "caml_resume_stack", [ Pv stack; Pv k ])) ]
-              ~exact:false
+              ~exact:(Global_flow.exact_call st.flow_info f 1)
               ~check:true
               ~f
               [ arg; k' ])
@@ -496,7 +503,7 @@ let cps_block ~st ~k pc block =
   ; branch = last
   }
 
-let cps_transform ~live_vars ~cps_needed p =
+let cps_transform ~live_vars ~flow_info ~cps_needed p =
   let closure_info = Hashtbl.create 16 in
   let cps_calls = ref Var.Set.empty in
   let p =
@@ -553,6 +560,7 @@ let cps_transform ~live_vars ~cps_needed p =
           ; is_continuation
           ; matching_exn_handler
           ; block_order = cfg.block_order
+          ; flow_info
           ; live_vars
           ; cps_calls
           }
@@ -818,6 +826,6 @@ let f (p, live_vars) =
   let cps_needed = Partial_cps_analysis.f p flow_info in
   let p, cps_needed = rewrite_toplevel ~cps_needed p in
   let p = split_blocks ~cps_needed p in
-  let p, cps_calls = cps_transform ~live_vars ~cps_needed p in
+  let p, cps_calls = cps_transform ~live_vars ~flow_info ~cps_needed p in
   if Debug.find "times" () then Format.eprintf "  effects: %a@." Timer.print t;
   p, cps_calls
diff --git a/compiler/tests-compiler/effects_call_opt.ml b/compiler/tests-compiler/effects_call_opt.ml
@@ -66,7 +66,7 @@ let%expect_test "test-compiler/lib-effects/effects_call_opt.ml" =
       return cont(0)}
     //end
     function test2(param,cont)
-     {function f(g,x,cont){return caml_cps_call2(g,x,cont)}
+     {function f(g,x,cont){return caml_cps_exact_call2(g,x,cont)}
       var _f_=7;
       function _g_(x,cont){return cont(x + 1 | 0)}
       return caml_cps_exact_call3
@@ -89,6 +89,6 @@ let%expect_test "test-compiler/lib-effects/effects_call_opt.ml" =
        {function f(x,cont){return caml_cps_call3(Stdlib_Printf[2],_a_,x,cont)}
         return [0,f]}
       var M1=F([0]),M2=F([0]),_b_=1,_c_=M1[1];
-      return caml_cps_call2
-              (_c_,_b_,function(_d_){return caml_cps_call2(M2[1],2,cont)})}
+      return caml_cps_exact_call2
+              (_c_,_b_,function(_d_){return caml_cps_exact_call2(M2[1],2,cont)})}
     //end |}]