diff options
Diffstat (limited to 'lib/compiler/src/v3_kernel.erl')
| -rw-r--r-- | lib/compiler/src/v3_kernel.erl | 41 |
1 files changed, 38 insertions, 3 deletions
diff --git a/lib/compiler/src/v3_kernel.erl b/lib/compiler/src/v3_kernel.erl index b184987625..b69ad416db 100644 --- a/lib/compiler/src/v3_kernel.erl +++ b/lib/compiler/src/v3_kernel.erl @@ -81,7 +81,7 @@ -export([module/2,format_error/1]). -import(lists, [map/2,foldl/3,foldr/3,mapfoldl/3,splitwith/2,member/2, - keymember/3,keyfind/3]). + keymember/3,keyfind/3,partition/2]). -import(ordsets, [add_element/2,del_element/2,union/2,union/1,subtract/2]). -import(cerl, [c_tuple/1]). @@ -1081,9 +1081,44 @@ select_bin_con(Cs0) -> end, Cs0), select_bin_con_1(Cs1). + select_bin_con_1(Cs) -> try - select_bin_int(Cs) + %% The usual way to match literals is to first extract the + %% value to a register, and then compare the register to the + %% literal value. Extracting the value is good if we need + %% compare it more than once. + %% + %% But we would like to combine the extracting and the + %% comparing into a single instruction if we know that + %% a binary segment must contain specific integer value + %% or the matching will fail, like in this example: + %% + %% <<42:8,...>> -> + %% <<42:8,...>> -> + %% . + %% . + %% . + %% <<42:8,...>> -> + %% <<>> -> + %% + %% The first segment must either contain the integer 42 + %% or the binary must end for the match to succeed. + %% + %% The way we do is to replace the generic #k_bin_seg{} + %% record with a #k_bin_int{} record if all clauses will + %% select the same literal integer (except for one or more + %% clauses that will end the binary). + + {BinSegs0,BinEnd} = + partition(fun (C) -> + clause_con(C) =:= k_bin_seg + end, Cs), + BinSegs = select_bin_int(BinSegs0), + case BinEnd of + [] -> BinSegs; + [_|_] -> BinSegs ++ [{k_bin_end,BinEnd}] + end catch throw:not_possible -> select_bin_con_2(Cs) @@ -1097,7 +1132,7 @@ select_bin_con_2([]) -> []. %% select_bin_int([Clause]) -> {k_bin_int,[Clause]} %% If the first pattern in each clause selects the same integer, -%% rewrite all clauses to use #k_bin_int{} (which will later to +%% rewrite all clauses to use #k_bin_int{} (which will later be %% translated to a bs_match_string/4 instruction). %% %% If it is not possible to do this rewrite, a 'not_possible' |