diff options
| -rw-r--r-- | lib/compiler/src/beam_ssa_type.erl | 49 |
1 files changed, 34 insertions, 15 deletions
diff --git a/lib/compiler/src/beam_ssa_type.erl b/lib/compiler/src/beam_ssa_type.erl index da73dc26f7..c163d544ce 100644 --- a/lib/compiler/src/beam_ssa_type.erl +++ b/lib/compiler/src/beam_ssa_type.erl @@ -1242,22 +1242,41 @@ band_type([Other,#b_literal{val=Int}], Ts) when is_integer(Int) -> band_type([_,_], _) -> t_integer(). band_type_1(Int, OtherSrc, Ts) -> - Type = band_type_2(Int, 0), OtherType = get_type(OtherSrc, Ts), - meet(Type, OtherType). - -band_type_2(N, Bits) when Bits < 64 -> - case 1 bsl Bits of - P when P =:= N + 1 -> - t_integer(0, N); - P when P > N + 1 -> - t_integer(); - _ -> - band_type_2(N, Bits+1) - end; -band_type_2(_, _) -> - %% Negative or large positive number. Give up. - t_integer(). + case OtherType of + #t_integer{elements={Min0,Max0}} when Max0 - Min0 < 1 bsl 256 -> + {Intersection, Union} = range_masks(Min0, Max0), + + Min = Intersection band Int, + Max = min(Max0, Union band Int), + + #t_integer{elements={Min,Max}}; + _ when Int >= 0 -> + %% The range is either unknown or too wide, conservatively assume + %% that the new range is 0 .. Int. + #t_integer{elements={0,Int}}; + _ when Int < 0 -> + %% We can't infer boundaries when the range is unknown and the + %% other operand is a negative number, as the latter sign-extends + %% to infinity and we can't express an inverted range at the + %% moment (cf. X band -8; either less than 7 or greater than 7). + #t_integer{} + end. + +%% Returns two bitmasks describing all possible values between From and To. +%% +%% The first contains the bits that are common to all values, and the second +%% contains the bits that are set by any value in the range. +range_masks(From, To) when From =< To -> + range_masks_1(From, To, 0, -1, 0). + +range_masks_1(From, To, BitPos, Intersection, Union) when From < To -> + range_masks_1(From + (1 bsl BitPos), To, BitPos + 1, + Intersection band From, Union bor From); +range_masks_1(_From, To, _BitPos, Intersection0, Union0) -> + Intersection = To band Intersection0, + Union = To bor Union0, + {Intersection, Union}. bs_match_type([#b_literal{val=Type}|Args]) -> bs_match_type(Type, Args). |