1 files changed, 22 insertions, 12 deletions
diff --git a/lib/compiler/src/beam_validator.erl b/lib/compiler/src/beam_validator.erl
index 09a5a6c104..0ae3b4ed1f 100644
--- a/lib/compiler/src/beam_validator.erl
+++ b/lib/compiler/src/beam_validator.erl
@@ -200,7 +200,7 @@ validate_0(Module, [{function,Name,Ar,Entry,Code}|Fs], Ft) ->
          numy=none :: none | undecided | index(),
          %% Available heap size.
          h=0,
-         %Available heap size for floats.
+         %%Available heap size for floats.
          hf=0,
          %% Floating point state.
          fls=undefined,
@@ -240,7 +240,7 @@ index_parameter_types([{function,_,_,Entry,Code0}|Fs], Acc0) ->
 	    Acc = index_parameter_types_1(Is, Entry, Acc0),
 	    index_parameter_types(Fs, Acc);
 	_ ->
-	    %% Something serious is wrong. Ignore it for now.
+	    %% Something is seriously wrong. Ignore it for now.
 	    %% It will be detected and diagnosed later.
 	    index_parameter_types(Fs, Acc0)
     end;
@@ -392,6 +392,23 @@ valfun_1(build_stacktrace=I, Vst) ->
     call(I, 1, Vst);
 valfun_1({move,Src,Dst}, Vst) ->
     assign(Src, Dst, Vst);
+valfun_1({swap,RegA,RegB}, Vst0) ->
+    assert_movable(RegA, Vst0),
+    assert_movable(RegB, Vst0),
+
+    %% We don't expect fragile registers to be swapped.
+    %% Therefore, we can conservatively make both registers
+    %% fragile if one of the register is fragile instead of
+    %% swapping the fragility of the registers.
+    Sources = [RegA,RegB],
+    Vst1 = propagate_fragility(RegA, Sources, Vst0),
+    Vst2 = propagate_fragility(RegB, Sources, Vst1),
+
+    %% Swap the value references.
+    VrefA = get_reg_vref(RegA, Vst2),
+    VrefB = get_reg_vref(RegB, Vst2),
+    Vst = set_reg_vref(VrefB, RegA, Vst2),
+    set_reg_vref(VrefA, RegB, Vst);
 valfun_1({fmove,Src,{fr,_}=Dst}, Vst) ->
     assert_type(float, Src, Vst),
     set_freg(Dst, Vst);
@@ -1848,16 +1865,9 @@ get_reg_vref({y,_}=Src, #vst{current=#st{ys=Ys}}) ->
     end.
 
 set_type(Type, #value_ref{}=Ref, #vst{current=#st{vs=Vs0}=St}=Vst) ->
-    case Vs0 of
-        #{ Ref := #value{}=Entry } ->
-            Vs = Vs0#{ Ref => Entry#value{type=Type} },
-            Vst#vst{current=St#st{vs=Vs}};
-        #{} ->
-            %% Dead references may happen during type inference and are not an
-            %% error in and of themselves. If a problem were to arise from this
-            %% it'll explode elsewhere.
-            Vst
-    end.
+    #{ Ref := #value{}=Entry } = Vs0,
+    Vs = Vs0#{ Ref => Entry#value{type=Type} },
+    Vst#vst{current=St#st{vs=Vs}}.
 
 new_value(Type, Op, Ss, #vst{current=#st{vs=Vs0}=St,ref_ctr=Counter}=Vst) ->
     Ref = #value_ref{id=Counter},