From abc4fd372d476821448dfb949bea4e28ab82ac26 Mon Sep 17 00:00:00 2001 From: Sverker Eriksson Date: Wed, 12 Jul 2017 17:09:10 +0200 Subject: erts: Fix bug in bxor of a big negative number Wrong result for (X bsl WS) bxor Y. where X is any negative integer Y is any integer that does not require more words than X WS is erlang:system_info(wordsize) or larger Fix: The subtraction of 1 (for 2-complement conversion) must be carried along all the way to the last words. --- erts/emulator/beam/big.c | 11 ++++-- erts/emulator/test/big_SUITE.erl | 53 +++++++++++++++++++++++++++ erts/emulator/test/big_SUITE_data/borders.dat | 35 ++++++++++++++++++ 3 files changed, 96 insertions(+), 3 deletions(-) diff --git a/erts/emulator/beam/big.c b/erts/emulator/beam/big.c index d1e46e3063..323cd6c518 100644 --- a/erts/emulator/beam/big.c +++ b/erts/emulator/beam/big.c @@ -1273,8 +1273,11 @@ static dsize_t I_bxor(ErtsDigit* x, dsize_t xl, short xsgn, *r++ = ~c ^ *y++; x++; } - while(xl--) - *r++ = ~*x++; + while(xl--) { + DSUBb(*x,0,b,c); + *r++ = ~c; + x++; + } } else { ErtsDigit b1, b2; @@ -1292,7 +1295,9 @@ static dsize_t I_bxor(ErtsDigit* x, dsize_t xl, short xsgn, x++; y++; } while(xl--) { - *r++ = *x++; + DSUBb(*x,0,b1,c1); + *r++ = c1; + x++; } } } diff --git a/erts/emulator/test/big_SUITE.erl b/erts/emulator/test/big_SUITE.erl index 3193d56e2a..c5bb228bc3 100644 --- a/erts/emulator/test/big_SUITE.erl +++ b/erts/emulator/test/big_SUITE.erl @@ -23,6 +23,7 @@ init_per_group/2,end_per_group/2]). -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, shift_limit_1/1, powmod/1, system_limit/1, toobig/1, otp_6692/1]). %% Internal exports. @@ -40,6 +41,7 @@ suite() -> [{ct_hooks,[ts_install_cth]}]. all() -> [t_div, eq_28, eq_32, eq_big, eq_math, big_literals, borders, negative, {group, big_float}, shift_limit_1, + bxor_2pow, powmod, system_limit, toobig, otp_6692]. groups() -> @@ -423,3 +425,54 @@ loop2(X,Y,N,M) -> end, loop2(X,Y,N+1,M). + +%% ERL-450 +bxor_2pow(_Config) -> + IL = lists:seq(8*3, 8*16, 4), + JL = lists:seq(0, 64), + [bxor_2pow_1((1 bsl I), (1 bsl J)) + || I <- IL, J <- JL], + ok. + +bxor_2pow_1(A, B) -> + for(-1,1, fun(Ad) -> + for(-1,1, fun(Bd) -> + bxor_2pow_2(A+Ad, B+Bd), + bxor_2pow_2(-A+Ad, B+Bd), + bxor_2pow_2(A+Ad, -B+Bd), + bxor_2pow_2(-A+Ad, -B+Bd) + end) + end). + +for(From, To, _Fun) when From > To -> + ok; +for(From, To, Fun) -> + Fun(From), + for(From+1, To, Fun). + +bxor_2pow_2(A, B) -> + Correct = my_bxor(A, B), + case A bxor B of + Correct -> ok; + Wrong -> + io:format("~.16b bxor ~.16b\n", [A,B]), + io:format("Expected ~.16b\n", [Correct]), + io:format("Got ~.16b\n", [Wrong]), + ct:fail({failed, 'bxor'}) + + end. + +%% Implement bxor without bxor +my_bxor(A, B) -> + my_bxor(A, B, 0, 0). + +my_bxor(0, 0, _, Acc) -> Acc; +my_bxor(-1, -1, _, Acc) -> Acc; +my_bxor(-1, 0, N, Acc) -> (-1 bsl N) bor Acc; % sign extension +my_bxor(0, -1, N, Acc) -> (-1 bsl N) bor Acc; % sign extension +my_bxor(A, B, N, Acc0) -> + Acc1 = case (A band 1) =:= (B band 1) of + true -> Acc0; + false -> Acc0 bor (1 bsl N) + end, + my_bxor(A bsr 1, B bsr 1, N+1, Acc1). diff --git a/erts/emulator/test/big_SUITE_data/borders.dat b/erts/emulator/test/big_SUITE_data/borders.dat index 52e4f35861..c38ff93383 100644 --- a/erts/emulator/test/big_SUITE_data/borders.dat +++ b/erts/emulator/test/big_SUITE_data/borders.dat @@ -1114,3 +1114,38 @@ 1 = 16#800000000000001 rem (-16#800000000000000). 0 = 16#FFFFFFFFFFFFFFF800000000 rem 16#FFFFFFFFFFFFFFF80. +% ERL-450 bxor of big negative 2-pow +-(1 bsl 8) bxor -1 = 16#ff. +-(1 bsl 16) bxor -1 = 16#ffff. +-(1 bsl 24) bxor -1 = 16#ffffff. +-(1 bsl 32) bxor -1 = 16#ffffffff. +-(1 bsl 40) bxor -1 = 16#ffffffffff. +-(1 bsl 48) bxor -1 = 16#ffffffffffff. +-(1 bsl 56) bxor -1 = 16#ffffffffffffff. +-(1 bsl 64) bxor -1 = 16#ffffffffffffffff. +-(1 bsl 72) bxor -1 = 16#ffffffffffffffffff. +-(1 bsl 80) bxor -1 = 16#ffffffffffffffffffff. +-(1 bsl 88) bxor -1 = 16#ffffffffffffffffffffff. +-(1 bsl 96) bxor -1 = 16#ffffffffffffffffffffffff. +-(1 bsl 104) bxor -1 = 16#ffffffffffffffffffffffffff. +-(1 bsl 112) bxor -1 = 16#ffffffffffffffffffffffffffff. +-(1 bsl 120) bxor -1 = 16#ffffffffffffffffffffffffffffff. +-(1 bsl 128) bxor -1 = 16#ffffffffffffffffffffffffffffffff. +-(1 bsl 136) bxor -1 = 16#ffffffffffffffffffffffffffffffffff. +-(1 bsl 8) bxor 1 = -16#ff. +-(1 bsl 16) bxor 1 = -16#ffff. +-(1 bsl 24) bxor 1 = -16#ffffff. +-(1 bsl 32) bxor 1 = -16#ffffffff. +-(1 bsl 40) bxor 1 = -16#ffffffffff. +-(1 bsl 48) bxor 1 = -16#ffffffffffff. +-(1 bsl 56) bxor 1 = -16#ffffffffffffff. +-(1 bsl 64) bxor 1 = -16#ffffffffffffffff. +-(1 bsl 72) bxor 1 = -16#ffffffffffffffffff. +-(1 bsl 80) bxor 1 = -16#ffffffffffffffffffff. +-(1 bsl 88) bxor 1 = -16#ffffffffffffffffffffff. +-(1 bsl 96) bxor 1 = -16#ffffffffffffffffffffffff. +-(1 bsl 104) bxor 1 = -16#ffffffffffffffffffffffffff. +-(1 bsl 112) bxor 1 = -16#ffffffffffffffffffffffffffff. +-(1 bsl 120) bxor 1 = -16#ffffffffffffffffffffffffffffff. +-(1 bsl 128) bxor 1 = -16#ffffffffffffffffffffffffffffffff. +-(1 bsl 136) bxor 1 = -16#ffffffffffffffffffffffffffffffffff. -- cgit v1.2.1