diff options
Diffstat (limited to 'lib/compiler/src/sys_core_fold.erl')
| -rw-r--r-- | lib/compiler/src/sys_core_fold.erl | 102 |
1 files changed, 94 insertions, 8 deletions
diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl index e302e2324d..e2b9213891 100644 --- a/lib/compiler/src/sys_core_fold.erl +++ b/lib/compiler/src/sys_core_fold.erl @@ -353,7 +353,12 @@ expr(#c_case{}=Case0, Ctxt, Sub) -> Case = Case1#c_case{arg=Arg2,clauses=Cs2}, warn_no_clause_match(Case1, Case), Expr = eval_case(Case, Sub), - bsm_an(Expr); + case move_case_into_arg(Case, Sub) of + impossible -> + bsm_an(Expr); + Other -> + expr(Other, Ctxt, sub_new_preserve_types(Sub)) + end; Other -> expr(Other, Ctxt, Sub) end; @@ -1940,7 +1945,9 @@ opt_bool_case_guard(Arg, [#c_clause{pats=[#c_literal{val=false}]}=Fc,Tc]) -> %% last clause is guaranteed to match so if there is only one clause %% with a pattern containing only variables then rewrite to a let. -eval_case(#c_case{arg=E,clauses=[#c_clause{pats=Ps0,body=B}]}, Sub) -> +eval_case(#c_case{arg=E,clauses=[#c_clause{pats=Ps0, + guard=#c_literal{val=true}, + body=B}]}=Case, Sub) -> Es = case cerl:is_c_values(E) of true -> cerl:values_es(E); false -> [E] @@ -1955,7 +1962,7 @@ eval_case(#c_case{arg=E,clauses=[#c_clause{pats=Ps0,body=B}]}, Sub) -> %% %% let <X,Y> = <SomeSideEffect(),SomeSideEffect()> in ... %% - %% because SomeSideEffect() would be called evaluated twice. + %% because SomeSideEffect() would be evaluated twice. %% %% Instead we must evaluate the case expression in an outer let %% like this: @@ -1964,11 +1971,19 @@ eval_case(#c_case{arg=E,clauses=[#c_clause{pats=Ps0,body=B}]}, Sub) -> %% let <X,Y> = <NewVar,NewVar> in ... %% Vs = make_vars([], length(Es)), - {true,Bs} = cerl_clauses:match_list(Ps0, Vs), - {Ps,As} = unzip(Bs), - InnerLet = cerl:c_let(Ps, core_lib:make_values(As), B), - Let = cerl:c_let(Vs, E, InnerLet), - expr(Let, sub_new(Sub)); + case cerl_clauses:match_list(Ps0, Vs) of + {false,_} -> + %% This can only happen if the Core Erlang code is + %% handwritten or generated by another code generator + %% than v3_core. Assuming that the Core Erlang program + %% is correct, the clause will always match at run-time. + Case; + {true,Bs} -> + {Ps,As} = unzip(Bs), + InnerLet = cerl:c_let(Ps, core_lib:make_values(As), B), + Let = cerl:c_let(Vs, E, InnerLet), + expr(Let, sub_new(Sub)) + end; eval_case(Case, _) -> Case. %% case_opt(CaseArg, [Clause]) -> {CaseArg,[Clause]}. @@ -2596,6 +2611,77 @@ opt_simple_let_2(Let, Vs0, Arg0, Body, value, Sub) -> value, Sub) end. +move_case_into_arg(#c_case{arg=#c_let{vars=OuterVars0,arg=OuterArg, + body=InnerArg0}=Outer, + clauses=InnerClauses}=Inner, Sub) -> + %% + %% case let <OuterVars> = <OuterArg> in <InnerArg> of + %% <InnerClauses> + %% end + %% + %% ==> + %% + %% let <OuterVars> = <OuterArg> + %% in case <InnerArg> of <InnerClauses> end + %% + ScopeSub0 = sub_subst_scope(Sub#sub{t=[]}), + {OuterVars,ScopeSub} = pattern_list(OuterVars0, ScopeSub0), + InnerArg = body(InnerArg0, ScopeSub), + Outer#c_let{vars=OuterVars,arg=OuterArg, + body=Inner#c_case{arg=InnerArg,clauses=InnerClauses}}; +move_case_into_arg(#c_case{arg=#c_case{arg=OuterArg, + clauses=[OuterCa0,OuterCb]}=Outer, + clauses=InnerClauses}=Inner0, Sub) -> + case is_failing_clause(OuterCb) of + true -> + #c_clause{pats=OuterPats0,guard=OuterGuard0, + body=InnerArg0} = OuterCa0, + %% + %% case case <OuterArg> of + %% <OuterPats> when <OuterGuard> -> <InnerArg> + %% <OuterCb> + %% ... + %% end of + %% <InnerClauses> + %% end + %% + %% ==> + %% + %% case <OuterArg> of + %% <OuterPats> when <OuterGuard> -> + %% case <InnerArg> of <InnerClauses> end + %% <OuterCb> + %% end + %% + ScopeSub0 = sub_subst_scope(Sub#sub{t=[]}), + {OuterPats,ScopeSub} = pattern_list(OuterPats0, ScopeSub0), + OuterGuard = guard(OuterGuard0, ScopeSub), + InnerArg = body(InnerArg0, ScopeSub), + Inner = Inner0#c_case{arg=InnerArg,clauses=InnerClauses}, + OuterCa = OuterCa0#c_clause{pats=OuterPats,guard=OuterGuard, + body=Inner}, + Outer#c_case{arg=OuterArg, + clauses=[OuterCa,OuterCb]}; + false -> + impossible + end; +move_case_into_arg(#c_case{arg=#c_seq{arg=OuterArg,body=InnerArg}=Outer, + clauses=InnerClauses}=Inner, _Sub) -> + %% + %% case do <OuterArg> <InnerArg> of + %% <InnerClauses> + %% end + %% + %% ==> + %% + %% do <OuterArg> + %% case <InnerArg> of <InerClauses> end + %% + Outer#c_seq{arg=OuterArg, + body=Inner#c_case{arg=InnerArg,clauses=InnerClauses}}; +move_case_into_arg(_, _) -> + impossible. + %% In guards only, rewrite a case in a let argument like %% %% let <Var> = case <> of |