From 5d0874a8f9fd617308d9024783db1e4e24268184 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Micha=C5=82=20Muska=C5=82a?= Date: Fri, 27 Apr 2018 12:40:07 +0200 Subject: Introduce is_map_key/2 guard BIF This complements the `map_get/2` guard BIF introduced in #1784. Rationale. `map_get/2` allows accessing map fields in guards, but it might be problematic in more complex guard expressions, for example: foo(X) when map_get(a, X) =:= 1 or is_list(X) -> ... The `is_list/1` part of the guard could never succeed since the `map_get/2` guard would fail the whole guard expression. In this situation, this could be solved by using `;` instead of `or` to separate the guards, but it is not possible in every case. To solve this situation, this PR proposes a `is_map_key/2` guard that allows to check if a map has key inside a guard before trying to access that key. When combined with `is_map/1` this allows to construct a purely boolean guard expression testing a value of a key in a map. Implementation. Given the use case motivating the introduction of this function, the PR contains compiler optimisations that produce optimial code for the following guard expression: foo(X) when is_map(X) and is_map_key(a, X) and map_get(a, X) =:= 1 -> ok; foo(_) -> error. Given all three tests share the failure label, the `is_map_key/2` and `is_map/2` tests are optimised away. As with `map_get/2` the `is_map_key/2` BIF is allowed in match specs. --- lib/compiler/src/beam_dead.erl | 20 ++++++++++++++++++++ lib/compiler/src/beam_peep.erl | 6 ++++++ lib/compiler/src/beam_type.erl | 3 +++ lib/compiler/src/erl_bifs.erl | 1 + lib/compiler/src/v3_codegen.erl | 6 ++++++ lib/compiler/test/map_SUITE.erl | 18 ++++++++++++++++++ 6 files changed, 54 insertions(+) (limited to 'lib/compiler') diff --git a/lib/compiler/src/beam_dead.erl b/lib/compiler/src/beam_dead.erl index dbbaae05eb..762c7bdf9e 100644 --- a/lib/compiler/src/beam_dead.erl +++ b/lib/compiler/src/beam_dead.erl @@ -392,6 +392,26 @@ backward([{bif,'or',{f,To0},[Dst,{atom,false}],Dst}=I|Is], D, _ -> backward(Is, D, [I|Acc]) end; +backward([{bif,map_get,{f,FF},[Key,Map],_}=I0, + {test,has_map_fields,{f,FT}=F,[Map|Keys0]}=I1|Is], D, Acc) when FF =/= 0 -> + case shortcut_label(FF, D) of + FT -> + case lists:delete(Key, Keys0) of + [] -> + backward([I0|Is], D, Acc); + Keys -> + Test = {test,has_map_fields,F,[Map|Keys]}, + backward([Test|Is], D, [I0|Acc]) + end; + _ -> + backward([I1|Is], D, [I0|Acc]) + end; +backward([{bif,map_get,{f,FF},[_,Map],_}=I0, + {test,is_map,{f,FT},[Map]}=I1|Is], D, Acc) when FF =/= 0 -> + case shortcut_label(FF, D) of + FT -> backward([I0|Is], D, Acc); + _ -> backward([I1|Is], D, [I0|Acc]) + end; backward([I|Is], D, Acc) -> backward(Is, D, [I|Acc]); backward([], _D, Acc) -> Acc. diff --git a/lib/compiler/src/beam_peep.erl b/lib/compiler/src/beam_peep.erl index eb3192fe8f..920fb00397 100644 --- a/lib/compiler/src/beam_peep.erl +++ b/lib/compiler/src/beam_peep.erl @@ -77,6 +77,12 @@ peep([{bif,tuple_size,_,[_]=Ops,Dst}=I|Is], SeenTests0, Acc) -> %% Kill all remembered tests that depend on the destination register. SeenTests = kill_seen(Dst, SeenTests1), peep(Is, SeenTests, [I|Acc]); +peep([{bif,map_get,_,[Key,Map],Dst}=I|Is], SeenTests0, Acc) -> + %% Pretend that we have seen {test,has_map_fields,_,[Map,Key]} + SeenTests1 = gb_sets:add({has_map_fields,[Map,Key]}, SeenTests0), + %% Kill all remembered tests that depend on the destination register. + SeenTests = kill_seen(Dst, SeenTests1), + peep(Is, SeenTests, [I|Acc]); peep([{bif,_,_,_,Dst}=I|Is], SeenTests0, Acc) -> %% Kill all remembered tests that depend on the destination register. SeenTests = kill_seen(Dst, SeenTests0), diff --git a/lib/compiler/src/beam_type.erl b/lib/compiler/src/beam_type.erl index 28f36db399..12da8c9446 100644 --- a/lib/compiler/src/beam_type.erl +++ b/lib/compiler/src/beam_type.erl @@ -462,6 +462,9 @@ update({set,[D],[Index,Reg],{bif,element,_}}, Ts0) -> end, Ts = tdb_meet(Reg, {tuple,min_size,MinSize,[]}, Ts0), tdb_store(D, any, Ts); +update({set,[D],[_Key,Map],{bif,map_get,_}}, Ts0) -> + Ts = tdb_meet(Map, map, Ts0), + tdb_store(D, any, Ts); update({set,[D],Args,{bif,N,_}}, Ts) -> Ar = length(Args), BoolOp = erl_internal:new_type_test(N, Ar) orelse diff --git a/lib/compiler/src/erl_bifs.erl b/lib/compiler/src/erl_bifs.erl index 70b36f029e..a7452aebc8 100644 --- a/lib/compiler/src/erl_bifs.erl +++ b/lib/compiler/src/erl_bifs.erl @@ -94,6 +94,7 @@ is_pure(erlang, is_function, 1) -> true; is_pure(erlang, is_integer, 1) -> true; is_pure(erlang, is_list, 1) -> true; is_pure(erlang, is_map, 1) -> true; +is_pure(erlang, is_map_key, 2) -> true; is_pure(erlang, is_number, 1) -> true; is_pure(erlang, is_pid, 1) -> true; is_pure(erlang, is_port, 1) -> true; diff --git a/lib/compiler/src/v3_codegen.erl b/lib/compiler/src/v3_codegen.erl index 8e73b613a0..9652a8476d 100644 --- a/lib/compiler/src/v3_codegen.erl +++ b/lib/compiler/src/v3_codegen.erl @@ -589,6 +589,7 @@ is_gc_bif(element, 2) -> false; is_gc_bif(get, 1) -> false; is_gc_bif(tuple_size, 1) -> false; is_gc_bif(map_get, 2) -> false; +is_gc_bif(is_map_key, 2) -> false; is_gc_bif(Bif, Arity) -> not (erl_internal:bool_op(Bif, Arity) orelse erl_internal:new_type_test(Bif, Arity) orelse @@ -1620,6 +1621,11 @@ test_cg(is_boolean, [#k_atom{val=Val}], Fail, I, Vdb, Bef, St) -> false -> [{jump,{f,Fail}}] end, {Is,Aft,St}; +test_cg(is_map_key, As, Fail, I, Vdb, Bef, St) -> + [Key,Map] = cg_reg_args(As, Bef), + Aft = clear_dead(Bef, I, Vdb), + F = {f,Fail}, + {[{test,is_map,F,[Map]},{test,has_map_fields,F,Map,{list,[Key]}}],Aft,St}; test_cg(Test, As, Fail, I, Vdb, Bef, St) -> Args = cg_reg_args(As, Bef), Aft = clear_dead(Bef, I, Vdb), diff --git a/lib/compiler/test/map_SUITE.erl b/lib/compiler/test/map_SUITE.erl index e98c295da6..6badc7a8b8 100644 --- a/lib/compiler/test/map_SUITE.erl +++ b/lib/compiler/test/map_SUITE.erl @@ -1203,12 +1203,18 @@ t_guard_bifs(Config) when is_list(Config) -> true = map_guard_empty_2(), true = map_guard_head(#{a=>1}), false = map_guard_head([]), + true = map_get_head(#{a=>1}), + false = map_get_head([]), + true = map_is_key_head(#{a=>1}), + false = map_is_key_head(#{}), true = map_guard_body(#{a=>1}), false = map_guard_body({}), true = map_guard_pattern(#{a=>1, <<"hi">> => "hi" }), false = map_guard_pattern("list"), true = map_guard_tautology(), true = map_guard_ill_map_size(), + true = map_field_check_sequence(#{a=>1}), + false = map_field_check_sequence(#{}), ok. map_guard_empty() when is_map(#{}); false -> true. @@ -1218,6 +1224,12 @@ map_guard_empty_2() when true; #{} andalso false -> true. map_guard_head(M) when is_map(M) -> true; map_guard_head(_) -> false. +map_get_head(M) when map_get(a, M) =:= 1 -> true; +map_get_head(_) -> false. + +map_is_key_head(M) when is_map_key(a, M) -> true; +map_is_key_head(M) -> false. + map_guard_body(M) -> is_map(M). map_guard_pattern(#{}) -> true; @@ -1227,6 +1239,12 @@ map_guard_tautology() when #{} =:= #{}; true -> true. map_guard_ill_map_size() when true; map_size(0) -> true. +map_field_check_sequence(M) + when is_map(M) andalso is_map_key(a, M) andalso (map_get(a, M) == 1) -> + true; +map_field_check_sequence(_) -> + false. + t_guard_sequence(Config) when is_list(Config) -> {1, "a"} = map_guard_sequence_1(#{seq=>1,val=>id("a")}), {2, "b"} = map_guard_sequence_1(#{seq=>2,val=>id("b")}), -- cgit v1.2.3