Merge pull request erlang#7272 from frej/frej/bif_binary_part3-is-ali…

…asing compiler: bif:binary_part/3 should alias its arguments
kevsmith · May 25, 2023 · 646be91 · 646be91
2 parents 87b7241 + 1dd55c4
commit 646be91
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diff --git a/lib/compiler/src/beam_ssa_alias.erl b/lib/compiler/src/beam_ssa_alias.erl
@@ -740,6 +740,11 @@ aa_bif(Dst, tl, Args, SS, AAS) ->
 %% TODO: Ignored for now, as we don't track what's inside maps.
 %% aa_bif(_Dst, map_get, _Args, SS, _AAS) ->
 %%     SS;
+aa_bif(Dst, binary_part, Args, SS, _AAS) ->
+    %% bif:binary_part/{2,3} is the only guard bif which could lead to
+    %% aliasing, it extracts a sub-binary with a reference to its
+    %% argument.
+    aa_set_aliased([Dst|Args], SS);
 aa_bif(Dst, Bif, Args, SS, _AAS) ->
     Arity = length(Args),
     case erl_internal:guard_bif(Bif, Arity)

diff --git a/lib/compiler/test/beam_ssa_check_SUITE_data/alias.erl b/lib/compiler/test/beam_ssa_check_SUITE_data/alias.erl
@@ -65,7 +65,8 @@
          stacktrace1/0,
          in_cons/0,
          make_fun/0,
-         gh6925/0]).
+         gh6925/0,
+         binary_part_aliases/2]).
 
 %% Trivial smoke test
 transformable0(L) ->
@@ -672,3 +673,13 @@ gh6925() ->
     A = << <<"x">> || true >>,
     B = <<A/binary, "z">>,
     {A, B}.
+
+%% Check that bif:binary_part/3 is correctly flagged as an operation
+%% which aliases its operands
+binary_part_aliases(A, B) ->
+%ssa% (_,_) when post_ssa_opt ->
+%ssa% X = bif:binary_part(_, _, _),
+%ssa% ret(X) {aliased => [X]}.
+    binary_part(<<>>, A, B).
+
+