From c6f5c65cae48bf08d08a79d790717eabc0884678 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Sun, 4 Nov 2018 11:39:20 +0100
Subject: Cover some code in beam_peep

Some lines in beam_peep were no longer covered when the sharing optimization
was added to beam_ssa_opt. Also remove some code from beam_peep that no
longer seems possible to cover.
---
 lib/compiler/src/beam_peep.erl    | 12 +++-----
 lib/compiler/test/match_SUITE.erl | 64 ++++++++++++++++++++++++++++++++++++---
 lib/compiler/test/misc_SUITE.erl  |  2 +-
 3 files changed, 65 insertions(+), 13 deletions(-)

diff --git a/lib/compiler/src/beam_peep.erl b/lib/compiler/src/beam_peep.erl
index 2323a439e9..5730e9704e 100644
--- a/lib/compiler/src/beam_peep.erl
+++ b/lib/compiler/src/beam_peep.erl
@@ -94,30 +94,26 @@ peep([{gc_bif,_,_,_,_,Dst}=I|Is], SeenTests0, Acc) ->
 peep([{jump,{f,L}},{label,L}=I|Is], _, Acc) ->
     %% Sometimes beam_jump has missed this optimization.
     peep(Is, gb_sets:empty(), [I|Acc]);
-peep([{select,Op,R,F,Vls0}|Is], SeenTests0, Acc0) ->
+peep([{select,select_val,R,F,Vls0}|Is], SeenTests0, Acc0) ->
     case prune_redundant_values(Vls0, F) of
 	[] ->
 	    %% No values left. Must convert to plain jump.
 	    I = {jump,F},
 	    peep([I|Is], gb_sets:empty(), Acc0);
-        [{atom,_}=Value,Lbl] when Op =:= select_val ->
+        [{atom,_}=Value,Lbl] ->
             %% Single value left. Convert to regular test.
             Is1 = [{test,is_eq_exact,F,[R,Value]},{jump,Lbl}|Is],
             peep(Is1, SeenTests0, Acc0);
-        [{integer,_}=Value,Lbl] when Op =:= select_val ->
+        [{integer,_}=Value,Lbl] ->
             %% Single value left. Convert to regular test.
             Is1 = [{test,is_eq_exact,F,[R,Value]},{jump,Lbl}|Is],
             peep(Is1, SeenTests0, Acc0);
-        [Arity,Lbl] when Op =:= select_tuple_arity ->
-            %% Single value left. Convert to regular test
-            Is1 = [{test,test_arity,F,[R,Arity]},{jump,Lbl}|Is],
-            peep(Is1, SeenTests0, Acc0);
 	[{atom,B1},Lbl,{atom,B2},Lbl] when B1 =:= not B2 ->
             %% Replace with is_boolean test.
             Is1 = [{test,is_boolean,F,[R]},{jump,Lbl}|Is],
             peep(Is1, SeenTests0, Acc0);
 	[_|_]=Vls ->
-	    I = {select,Op,R,F,Vls},
+	    I = {select,select_val,R,F,Vls},
 	    peep(Is, gb_sets:empty(), [I|Acc0])
     end;
 peep([{get_map_elements,Fail,Src,List}=I|Is], _SeenTests, Acc0) ->
diff --git a/lib/compiler/test/match_SUITE.erl b/lib/compiler/test/match_SUITE.erl
index 229c3093d7..eed2a31f70 100644
--- a/lib/compiler/test/match_SUITE.erl
+++ b/lib/compiler/test/match_SUITE.erl
@@ -483,9 +483,8 @@ sel_same_value2(V) when V =:= 42; V =:= 43 ->
 sel_same_value2(_) ->
     error.
 
-%% Test deconstruction of select_val instructions in beam_peep into
-%% regular tests with just one possible value left. Hitting proper cases
-%% in beam_peep relies on unification of labels by beam_jump.
+%% Test deconstruction of select_val instructions to regular tests
+%% with zero or one values left.
 
 deselectify(Config) when is_list(Config) ->
     one_or_other = desel_tuple_arity({1}),
@@ -506,7 +505,31 @@ deselectify(Config) when is_list(Config) ->
 
     one_or_other = dsel_atom_typecheck(one),
     two = dsel_atom_typecheck(two),
-    one_or_other = dsel_atom_typecheck(three).
+    one_or_other = dsel_atom_typecheck(three),
+
+    %% Cover deconstruction of select_val instructions in
+    %% beam_peep.
+
+    stop = dsel_peek_0(stop),
+    ignore = dsel_peek_0(ignore),
+    Config = dsel_peek_0(Config),
+
+    stop = dsel_peek_1(stop, any),
+    Config = dsel_peek_1(ignore, Config),
+    other = dsel_peek_1(other, ignored),
+
+    0 = dsel_peek_2(0, any),
+    Config = dsel_peek_2(1, Config),
+    2 = dsel_peek_2(2, ignored),
+
+    true = dsel_peek_3(true),
+    false = dsel_peek_3(false),
+    {error,Config} = dsel_peek_3(Config),
+
+    ok.
+
+%% The following will be optimized by the sharing optimizations
+%% in beam_ssa_opt.
 
 desel_tuple_arity(Tuple) when is_tuple(Tuple) ->
     case Tuple of
@@ -543,6 +566,39 @@ dsel_atom_typecheck(Val) when is_atom(Val) ->
         _ -> one_or_other
     end.
 
+%% The following functions are carefully crafted so that the sharing
+%% optimizations in beam_ssa_opt can't be applied. After applying the
+%% beam_jump:eliminate_moves/1 optimization and beam_clean:clean_labels/1
+%% has unified labels, beam_peep is able to optimize these functions.
+
+dsel_peek_0(A0) ->
+    case id(A0) of
+        stop ->   stop;
+        ignore -> ignore;
+        A ->      A
+    end.
+
+dsel_peek_1(A0, B) ->
+    case id(A0) of
+        stop ->   stop;
+        ignore -> B;
+        A ->      A
+    end.
+
+dsel_peek_2(A0, B) ->
+    case id(A0) of
+        0 -> 0;
+        1 -> B;
+        A -> A
+    end.
+
+dsel_peek_3(A0) ->
+    case id(A0) of
+        true ->  true;
+        false -> false;
+        Other -> {error,Other}
+    end.
+
 underscore(Config) when is_list(Config) ->
     case Config of
 	[] ->
diff --git a/lib/compiler/test/misc_SUITE.erl b/lib/compiler/test/misc_SUITE.erl
index bc034dcc29..2a6303ece8 100644
--- a/lib/compiler/test/misc_SUITE.erl
+++ b/lib/compiler/test/misc_SUITE.erl
@@ -260,7 +260,7 @@ silly_coverage(Config) when is_list(Config) ->
 		 [{function,foo,0,2,
 		   [{label,1},
 		    {func_info,{atom,?MODULE},{atom,foo},0},
-		    {label,2},{select,op,r,{f,2},[{f,2}]}]}],
+		    {label,2},{select,select_val,r,{f,2},[{f,2}]}]}],
 		 2},
     expect_error(fun() -> beam_peep:module(PeepInput, []) end),
 
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