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authorMichał Muskała <[email protected]>2018-04-27 12:40:07 +0200
committerMichał Muskała <[email protected]>2018-04-29 17:03:43 +0200
commit5d0874a8f9fd617308d9024783db1e4e24268184 (patch)
treeac61f2f0f8d7f7483af9e17df44b49aeb049e695 /lib/compiler
parentd423a7af502227afcdcf7d2a1efecded85ea95fb (diff)
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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.
Diffstat (limited to 'lib/compiler')
-rw-r--r--lib/compiler/src/beam_dead.erl20
-rw-r--r--lib/compiler/src/beam_peep.erl6
-rw-r--r--lib/compiler/src/beam_type.erl3
-rw-r--r--lib/compiler/src/erl_bifs.erl1
-rw-r--r--lib/compiler/src/v3_codegen.erl6
-rw-r--r--lib/compiler/test/map_SUITE.erl18
6 files changed, 54 insertions, 0 deletions
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")}),