From 01e70c30d837887acbbb91d13ec2d8d1cb616c7e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?John=20H=C3=B6gberg?= <john@erlang.org>
Date: Wed, 3 Apr 2019 12:31:37 +0200
Subject: erts: Optimize arithmetic ops using overflow intrinsics

---
 erts/emulator/test/Makefile        |   1 +
 erts/emulator/test/small_SUITE.erl | 115 +++++++++++++++++++++++++++++++++++++
 2 files changed, 116 insertions(+)
 create mode 100644 erts/emulator/test/small_SUITE.erl

(limited to 'erts/emulator/test')

diff --git a/erts/emulator/test/Makefile b/erts/emulator/test/Makefile
index 8c2054cb51..28775b6f02 100644
--- a/erts/emulator/test/Makefile
+++ b/erts/emulator/test/Makefile
@@ -124,6 +124,7 @@ MODULES= \
 	send_term_SUITE \
 	sensitive_SUITE \
 	signal_SUITE \
+	small_SUITE \
 	smoke_test_SUITE \
 	$(SOCKET_MODULES) \
 	statistics_SUITE \
diff --git a/erts/emulator/test/small_SUITE.erl b/erts/emulator/test/small_SUITE.erl
new file mode 100644
index 0000000000..00a02e5560
--- /dev/null
+++ b/erts/emulator/test/small_SUITE.erl
@@ -0,0 +1,115 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 2019. All Rights Reserved.
+%%
+%% Licensed under the Apache License, Version 2.0 (the "License");
+%% you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%%     http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%
+%% %CopyrightEnd%
+%%
+-module(small_SUITE).
+
+-export([all/0, suite/0]).
+-export([edge_cases/1]).
+
+-include_lib("common_test/include/ct.hrl").
+
+suite() ->
+    [{ct_hooks,[ts_install_cth]},
+     {timetrap, {minutes, 1}}].
+
+all() ->
+    [edge_cases].
+
+edge_cases(Config) when is_list(Config) ->
+    {MinSmall, MaxSmall} = Limits = determine_small_limits(0),
+    ct:pal("Limits = ~p", [Limits]),
+
+    true = (MaxSmall + 1) =:= MaxSmall + id(1),
+    true = (MinSmall - 1) =:= MinSmall - id(1),
+    true = (MaxSmall + 1) > id(MaxSmall),
+    true = (MinSmall - 1) < id(MinSmall),
+    -1 = MinSmall + id(MaxSmall),
+    -1 = MaxSmall + id(MinSmall),
+
+    false = is_small(MinSmall * -1),
+    false = is_small(MinSmall - id(1)),
+    false = is_small(MinSmall - 1),
+    false = is_small(MaxSmall + id(1)),
+
+    Lower = lists:seq(MinSmall, MinSmall + 128),
+    Upper = lists:seq(MaxSmall, MaxSmall - 128, -1),
+    Pow2 = seq_pow2(MinSmall, MaxSmall),
+    NearZero = lists:seq(-128, 128),
+
+    ok = test_combinations([Lower, Upper, Pow2, NearZero], MinSmall, MaxSmall),
+
+    ok.
+
+test_combinations([As | Rest]=TestVectors, MinS, MaxS) ->
+    [begin
+        _ = [arith_test(A, B, MinS, MaxS) || B <- Bs]
+     end || A <- As, Bs <- TestVectors],
+    test_combinations(Rest, MinS, MaxS);
+test_combinations([], _MinS, _MaxS) ->
+    ok.
+
+%% Builds a sequence of all powers of 2 between MinSmall and MaxSmall
+seq_pow2(MinSmall, MaxSmall) ->
+    sp2_1(MinSmall, MinSmall, MaxSmall).
+
+sp2_1(N, _MinS, MaxS) when N >= MaxS ->
+    [];
+sp2_1(-1, MinS, MaxS) ->
+    [-1 | sp2_1(1, MinS, MaxS)];
+sp2_1(N, MinS, MaxS) when N < 0 ->
+    [N | sp2_1(N bsr 1, MinS, MaxS)];
+sp2_1(N, MinS, MaxS) when N > 0 ->
+    [N | sp2_1(N bsl 1, MinS, MaxS)].
+
+arith_test(A, B, MinS, MaxS) ->
+    verify_kind(A + B, MinS, MaxS),
+    verify_kind(B + A, MinS, MaxS),
+    verify_kind(A - B, MinS, MaxS),
+    verify_kind(B - A, MinS, MaxS),
+    verify_kind(A * B, MinS, MaxS),
+    verify_kind(B * A, MinS, MaxS),
+
+    true = A + B =:= apply(erlang, id('+'), [A, B]),
+    true = A - B =:= apply(erlang, id('-'), [A, B]),
+    true = A * B =:= apply(erlang, id('*'), [A, B]),
+
+    true = A + B =:= B + id(A),
+    true = A - B =:= A + id(-B),
+    true = B - A =:= B + id(-A),
+    true = A * B =:= B * id(A),
+
+    true = B =:= 0 orelse ((A * B) div id(B) =:= A),
+    true = A =:= 0 orelse ((B * A) div id(A) =:= B),
+
+    ok.
+
+%% Verifies that N is a small when it should be
+verify_kind(N, MinS, MaxS) ->
+    true = is_small(N) =:= (N >= MinS andalso N =< MaxS).
+
+is_small(N) when is_integer(N) ->
+    0 =:= erts_debug:flat_size(N).
+
+determine_small_limits(N) ->
+    case is_small(-1 bsl N) of
+        true -> determine_small_limits(N + 1);
+        false -> {-1 bsl (N - 1), (1 bsl (N - 1)) - 1}
+    end.
+
+id(I) -> I.
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