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File 3504-Support-a-definition-with-non-zero-arity-in-letrecs.patch of Package erlang (Revision a2c80b217d02c910313d01e8533b91ce)

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From f546115ed4bdb0abcee2f4694c49860732585974 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Mon, 1 Nov 2021 06:20:24 +0100
Subject: [PATCH 04/12] Support a definition with non-zero arity in letrecs

Teach the `v3_kernel` and `beam_kernel_to_ssa` passes to handle
a `letrec` with the `letrec_goto` option, where the defined function
has an arity of one or higher. Also update Dialyzer to handle such
letrecs.

This enhanced `letrec` will come in handy for implementing
EEP 49 in the next commit.
---
 lib/compiler/src/beam_kernel_to_ssa.erl  | 29 +++++++++++++-------
 lib/compiler/src/v3_kernel.erl           | 34 +++++++++++++++---------
 lib/compiler/src/v3_kernel.hrl           |  4 +--
 lib/compiler/src/v3_kernel_pp.erl        |  7 ++---
 lib/dialyzer/src/dialyzer_clean_core.erl |  7 +++--
 5 files changed, 53 insertions(+), 28 deletions(-)

diff --git a/lib/compiler/src/beam_kernel_to_ssa.erl b/lib/compiler/src/beam_kernel_to_ssa.erl
index 034130e5aa..52a68efbb6 100644
--- a/lib/compiler/src/beam_kernel_to_ssa.erl
+++ b/lib/compiler/src/beam_kernel_to_ssa.erl
@@ -133,20 +133,31 @@ cg(#k_return{args=[Ret0]}, St) ->
 cg(#k_break{args=Bs}, #cg{break=Br}=St) ->
     Args = ssa_args(Bs, St),
     {[#cg_break{args=Args,phi=Br}],St};
-cg(#k_letrec_goto{label=Label,first=First,then=Then,ret=Rs},
+cg(#k_letrec_goto{label=Label,vars=Vs0,first=First,then=Then,ret=Rs},
    #cg{break=OldBreak,labels=Labels0}=St0) ->
     {Tf,St1} = new_label(St0),
     {B,St2} = new_label(St1),
     Labels = Labels0#{Label=>Tf},
-    {Fis,St3} = cg(First, St2#cg{labels=Labels,break=B}),
-    {Sis,St4} = cg(Then, St3),
-    St5 = St4#cg{labels=Labels0},
-    {BreakVars,St} = new_ssa_vars(Rs, St5),
-    Phi = #cg_phi{vars=BreakVars},
-    {Fis ++ [{label,Tf}] ++ Sis ++ [{label,B},Phi],St#cg{break=OldBreak}};
-cg(#k_goto{label=Label}, #cg{labels=Labels}=St) ->
+    {Vs,St3} = new_ssa_vars(Vs0, St2),
+    {Fis,St4} = cg(First, St3#cg{labels=Labels,break=B}),
+    {Sis,St5} = cg(Then, St4),
+    St6 = St5#cg{labels=Labels0},
+    {BreakVars,St} = new_ssa_vars(Rs, St6),
+    PostPhi = #cg_phi{vars=BreakVars},
+    FailPhi = case Vs of
+                  [] -> [];
+                  [_|_] -> [#cg_phi{vars=Vs}]
+              end,
+    {Fis ++ [{label,Tf}] ++ FailPhi ++ Sis ++ [{label,B},PostPhi],
+     St#cg{break=OldBreak}};
+cg(#k_goto{label=Label,args=[]}, #cg{labels=Labels}=St) ->
     Branch = map_get(Label, Labels),
-    {[make_uncond_branch(Branch)],St}.
+    {[make_uncond_branch(Branch)],St};
+cg(#k_goto{label=Label,args=As0}, #cg{labels=Labels}=St) ->
+    As = ssa_args(As0, St),
+    Branch = map_get(Label, Labels),
+    Break = #cg_break{args=As,phi=Branch},
+    {[Break],St}.
 
 %% match_cg(Matc, [Ret], State) -> {[Ainstr],State}.
 %%  Generate code for a match.
diff --git a/lib/compiler/src/v3_kernel.erl b/lib/compiler/src/v3_kernel.erl
index 6fe4da764a..b2ddf1afd5 100644
--- a/lib/compiler/src/v3_kernel.erl
+++ b/lib/compiler/src/v3_kernel.erl
@@ -385,19 +385,27 @@ letrec_local_function(A, Cfs, Cb, Sub0, St0) ->
 %% Implement letrec with the single definition as a label and each
 %% apply of it as a goto.
 
-letrec_goto([{#c_var{name={Label,0}},Cfail}], Cb, Sub0,
+letrec_goto([{#c_var{name={Label,_Arity}},Cfail}], Cb, Sub0,
             #kern{labels=Labels0}=St0) ->
+    #c_fun{vars=FunVars,body=FunBody} = Cfail,
+    {Kvars,{FunSub,St1}} =
+        mapfoldl(fun(#c_var{anno=A,name=V}, {SubInt,StInt0}) ->
+                         {New,StInt1} = new_var_name(StInt0),
+                         {#k_var{anno=A,name=New},
+                          {set_vsub(V, New, SubInt),
+                           StInt1#kern{ds=sets:add_element(New, StInt1#kern.ds)}}}
+                 end, {Sub0,St0}, FunVars),
     Labels = sets:add_element(Label, Labels0),
-    {Kb,Pb,St1} = body(Cb, Sub0, St0#kern{labels=Labels}),
-    #c_fun{body=FailBody} = Cfail,
-    {Kfail,Fb,St2} = body(FailBody, Sub0, St1),
+    {Kb,Pb,St2} = body(Cb, Sub0, St1#kern{labels=Labels}),
+    {Kfail,Fb,St3} = body(FunBody, FunSub, St2),
     case {Kb,Kfail,Fb} of
         {#k_goto{label=Label},#k_goto{}=InnerGoto,[]} ->
-            {InnerGoto,Pb,St2};
+            {InnerGoto,Pb,St3};
         {_,_,_} ->
-            St3 = St2#kern{labels=Labels0},
-            Alt = #k_letrec_goto{label=Label,first=Kb,then=pre_seq(Fb, Kfail)},
-            {Alt,Pb,St3}
+            St4 = St3#kern{labels=Labels0},
+            Alt = #k_letrec_goto{label=Label,vars=Kvars,
+                                 first=Kb,then=pre_seq(Fb, Kfail)},
+            {Alt,Pb,St4}
     end.
 
 %% translate_match_fail(Arg, Sub, Anno, St) -> {Kexpr,[PreKexpr],State}.
@@ -561,10 +569,11 @@ match_vars(Ka, St0) ->
 %%  Transform application.
 
 c_apply(A, #c_var{anno=Ra,name={F0,Ar}}, Cargs, Sub, #kern{labels=Labels}=St0) ->
-    case Ar =:= 0 andalso sets:is_element(F0, Labels) of
+    case sets:is_element(F0, Labels) of
         true ->
             %% This is a goto to a label in a letrec_goto construct.
-            {#k_goto{label=F0},[],St0};
+            {Kargs,Ap,St1} = atomic_list(Cargs, Sub, St0),
+            {#k_goto{label=F0,args=Kargs},Ap,St1};
         false ->
             {Kargs,Ap,St1} = atomic_list(Cargs, Sub, St0),
             F1 = get_fsub(F0, Ar, Sub),         %Has it been rewritten
@@ -2002,11 +2011,12 @@ uexpr(#k_local{anno=A,name=Name,arity=Arity}, {break,Rs}, St) ->
                  args=[#k_local{name=Name,arity=Arity+FreeCount} | Fvs],
                  ret=Rs},
     {Bif,Free,St};
-uexpr(#k_letrec_goto{anno=A,first=F0,then=T0}=MatchAlt, Br, St0) ->
+uexpr(#k_letrec_goto{anno=A,vars=Vs,first=F0,then=T0}=MatchAlt, Br, St0) ->
     Rs = break_rets(Br),
+    Ns = lit_list_vars(Vs),
     {F1,Fu,St1} = ubody(F0, Br, St0),
     {T1,Tu,St2} = ubody(T0, Br, St1),
-    Used = union(Fu, Tu),
+    Used = subtract(union(Fu, Tu), Ns),
     {MatchAlt#k_letrec_goto{anno=A,first=F1,then=T1,ret=Rs},Used,St2};
 uexpr(Lit, {break,Rs0}, St0) ->
     %% Transform literals to puts here.
diff --git a/lib/compiler/src/v3_kernel.hrl b/lib/compiler/src/v3_kernel.hrl
index 76987640e8..8d3e5dd7e7 100644
--- a/lib/compiler/src/v3_kernel.hrl
+++ b/lib/compiler/src/v3_kernel.hrl
@@ -56,8 +56,8 @@
 -record(k_try_enter, {anno=[],arg,vars,body,evars,handler}).
 -record(k_catch, {anno=[],body,ret=[]}).
 
--record(k_letrec_goto, {anno=[],label,first,then,ret=[]}).
--record(k_goto, {anno=[],label}).
+-record(k_letrec_goto, {anno=[],label,vars=[],first,then,ret=[]}).
+-record(k_goto, {anno=[],label,args=[]}).
 
 -record(k_match, {anno=[],body,ret=[]}).
 -record(k_alt, {anno=[],first,then}).
diff --git a/lib/compiler/src/v3_kernel_pp.erl b/lib/compiler/src/v3_kernel_pp.erl
index 2c2bd498a9..d1b075ce0f 100644
--- a/lib/compiler/src/v3_kernel_pp.erl
+++ b/lib/compiler/src/v3_kernel_pp.erl
@@ -173,10 +173,11 @@ format_1(#k_alt{first=O,then=T}, Ctxt) ->
      format(O, Ctxt1),
      nl_indent(Ctxt1),
      format(T, Ctxt1)];
-format_1(#k_letrec_goto{label=Label,first=First,then=Then,ret=Rs}, Ctxt) ->
+format_1(#k_letrec_goto{label=Label,vars=Vs,first=First,then=Then,ret=Rs}, Ctxt) ->
     Ctxt1 = ctxt_bump_indent(Ctxt, Ctxt#ctxt.item_indent),
     ["letrec_goto ",
      atom_to_list(Label),
+     format_args(Vs, Ctxt),
      nl_indent(Ctxt1),
      format(Then, Ctxt1),
      nl_indent(Ctxt1),
@@ -185,8 +186,8 @@ format_1(#k_letrec_goto{label=Label,first=First,then=Then,ret=Rs}, Ctxt) ->
      "end",
      format_ret(Rs, Ctxt1)
     ];
-format_1(#k_goto{label=Label}, _Ctxt) ->
-    ["goto ",atom_to_list(Label)];
+format_1(#k_goto{label=Label,args=As}, Ctxt) ->
+    ["goto ",atom_to_list(Label),format_args(As, Ctxt)];
 format_1(#k_select{var=V,types=Cs}, Ctxt) ->
     Ctxt1 = ctxt_bump_indent(Ctxt, 2),
     ["select ",
diff --git a/lib/dialyzer/src/dialyzer_clean_core.erl b/lib/dialyzer/src/dialyzer_clean_core.erl
index 071e2eccad..820ce19a06 100644
--- a/lib/dialyzer/src/dialyzer_clean_core.erl
+++ b/lib/dialyzer/src/dialyzer_clean_core.erl
@@ -109,6 +109,7 @@ clean_letrec(Tree) ->
       FunBody = cerl:fun_body(Fun),
       FunBody1 = clean(FunBody),
       Body = clean(cerl:letrec_body(Tree)),
+      FunVars = cerl:fun_vars(Fun),
       case dialyzer_ignore(Body) of
         true ->
           %% The body of the letrec directly transfer controls to
@@ -152,8 +153,10 @@ clean_letrec(Tree) ->
           %%    end
           %%
           PrimopUnknown = cerl:c_primop(cerl:abstract(dialyzer_unknown), []),
-          Clauses = [cerl:c_clause([cerl:abstract(a)], Body),
-                     cerl:c_clause([cerl:abstract(b)], FunBody1)],
+          PatA = [cerl:abstract(a)],
+          PatB = [cerl:c_tuple([cerl:abstract(b)|FunVars])],
+          Clauses = [cerl:c_clause(PatA, Body),
+                     cerl:c_clause(PatB, FunBody1)],
           cerl:c_case(PrimopUnknown, Clauses)
       end;
     false ->
-- 
2.34.1

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File 3504-Support-a-definition-with-non-zero-arity-in-letrecs.patch of Package erlang (Revision a2c80b217d02c910313d01e8533b91ce)

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