Merge pull request #1596 from bjorng/bjorn/enhance-try-catch

(Slightly) optimize catch and try/catch

OTP-14683

3 files changed, 19 insertions, 2 deletions

diff --git a/lib/compiler/src/beam_receive.erl b/lib/compiler/src/beam_receive.erl
index 1403e1e05e..468460eedf 100644
--- a/lib/compiler/src/beam_receive.erl
+++ b/lib/compiler/src/beam_receive.erl
@@ -207,6 +207,8 @@ opt_update_regs({label,Lbl}, R, L) ->
 	    %% A catch label for a previously seen catch instruction is OK.
 	    {R,L}
     end;
+opt_update_regs({'try',_,{f,Lbl}}, R, L) ->
+    {R,gb_sets:add(Lbl, L)};
 opt_update_regs({try_end,_}, R, L) ->
     {R,L};
 opt_update_regs({line,_}, R, L) ->
diff --git a/lib/compiler/src/beam_utils.erl b/lib/compiler/src/beam_utils.erl
index a4c65397df..00f396c246 100644
--- a/lib/compiler/src/beam_utils.erl
+++ b/lib/compiler/src/beam_utils.erl
@@ -825,8 +825,14 @@ live_opt([{select,_,Src,Fail,List}=I|Is], Regs0, D, Acc) ->
     Regs1 = x_live([Src], Regs0),
     Regs = live_join_labels([Fail|List], D, Regs1),
     live_opt(Is, Regs, D, [I|Acc]);
-live_opt([{try_case,_}=I|Is], _, D, Acc) ->
-    live_opt(Is, live_call(1), D, [I|Acc]);
+live_opt([{try_case,Y}=I|Is], Regs0, D, Acc) ->
+    Regs = live_call(1),
+    case Regs0 of
+        0 ->
+            live_opt(Is, Regs, D, [{try_end,Y}|Acc]);
+        _ ->
+            live_opt(Is, live_call(1), D, [I|Acc])
+    end;
 live_opt([{loop_rec,_Fail,_Dst}=I|Is], _, D, Acc) ->
     live_opt(Is, 0, D, [I|Acc]);
 live_opt([timeout=I|Is], _, D, Acc) ->
diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl
index f3f315935a..df880ff784 100644
--- a/lib/compiler/src/sys_core_fold.erl
+++ b/lib/compiler/src/sys_core_fold.erl
@@ -418,6 +418,15 @@ expr(#c_call{module=M0,name=N0}=Call0, Ctxt, Sub) ->
 expr(#c_primop{args=As0}=Prim, _, Sub) ->
     As1 = expr_list(As0, value, Sub),
     Prim#c_primop{args=As1};
+expr(#c_catch{anno=Anno,body=B}, effect, Sub) ->
+    %% When the return value of the 'catch' is ignored, we can replace it
+    %% with a try/catch to avoid building a stack trace when an exception
+    %% occurs.
+    Var = #c_var{name='catch_value'},
+    Evs = [#c_var{name='Class'},#c_var{name='Reason'},#c_var{name='Stk'}],
+    Try = #c_try{anno=Anno,arg=B,vars=[Var],body=Var,
+                 evars=Evs,handler=void()},
+    expr(Try, effect, Sub);
 expr(#c_catch{body=B0}=Catch, _, Sub) ->
     %% We can remove catch if the value is simple
     B1 = body(B0, value, Sub),