Merge branch 'sverker/big-band-bug/ERL-804/OTP-15487' into maint

* sverker/big-band-bug/ERL-804/OTP-15487:
  erts: Fix bug in 'band' of two negative numbers, one big

1 files changed, 37 insertions, 2 deletions

diff --git a/erts/emulator/test/big_SUITE.erl b/erts/emulator/test/big_SUITE.erl
index 5b602dd4dc..3b9b9e5989 100644
--- a/erts/emulator/test/big_SUITE.erl
+++ b/erts/emulator/test/big_SUITE.erl
@@ -24,7 +24,7 @@
 
 -export([t_div/1, eq_28/1, eq_32/1, eq_big/1, eq_math/1, big_literals/1,
 	 borders/1, negative/1, big_float_1/1, big_float_2/1,
-         bxor_2pow/1,
+         bxor_2pow/1, band_2pow/1,
 	 shift_limit_1/1, powmod/1, system_limit/1, toobig/1, otp_6692/1]).
 
 %% Internal exports.
@@ -43,7 +43,7 @@ suite() ->
 all() -> 
     [t_div, eq_28, eq_32, eq_big, eq_math, big_literals,
      borders, negative, {group, big_float}, shift_limit_1,
-     bxor_2pow,
+     bxor_2pow, band_2pow,
      powmod, system_limit, toobig, otp_6692].
 
 groups() -> 
@@ -472,3 +472,38 @@ my_bxor(A, B, N, Acc0) ->
                false -> Acc0 bor (1 bsl N)
           end,
     my_bxor(A bsr 1, B bsr 1, N+1, Acc1).
+
+
+%% ERL-804
+band_2pow(_Config) ->
+    IL = lists:seq(8*3, 8*16, 4),
+    JL = lists:seq(0, 64),
+    [band_2pow_1((1 bsl I), (1 bsl J))
+     || I <- IL, J <- JL],
+    ok.
+
+band_2pow_1(A, B) ->
+    for(-1,1, fun(Ad) ->
+                      for(-1,1, fun(Bd) ->
+                                        band_2pow_2(A+Ad, B+Bd),
+                                        band_2pow_2(-A+Ad, B+Bd),
+                                        band_2pow_2(A+Ad, -B+Bd),
+                                        band_2pow_2(-A+Ad, -B+Bd)
+                                end)
+              end).
+
+band_2pow_2(A, B) ->
+    Correct = my_band(A, B),
+    case A band B of
+        Correct -> ok;
+        Wrong ->
+            io:format("~.16# band ~.16#\n", [A,B]),
+            io:format("Expected ~.16#\n", [Correct]),
+            io:format("Got      ~.16#\n", [Wrong]),
+            ct:fail({failed, 'band'})
+
+    end.
+
+%% Implement band without band
+my_band(A, B) ->
+    bnot ((bnot A) bor (bnot B)).