diff options
author | Björn Gustavsson <[email protected]> | 2015-01-23 13:12:09 +0100 |
---|---|---|
committer | Björn Gustavsson <[email protected]> | 2015-02-03 09:39:32 +0100 |
commit | 4babd738633953a09ce3314ed89d0933063b4ef7 (patch) | |
tree | 4975109d3d64e76fdc4ba5a7e7e3ecdef586ef11 /lib/compiler/test/core_fold_SUITE.erl | |
parent | cd1eaf0116190ab72f3a792b74be99eda5dd31eb (diff) | |
download | otp-4babd738633953a09ce3314ed89d0933063b4ef7.tar.gz otp-4babd738633953a09ce3314ed89d0933063b4ef7.tar.bz2 otp-4babd738633953a09ce3314ed89d0933063b4ef7.zip |
Teach case_opt/3 to avoid unnecessary building
Given this code:
f(S) ->
F0 = F1 = {S,S},
[F0,F1].
case_opt/3 would "optimize" it like this:
f(S) ->
F1 = {S,S},
F0 = {S,S},
[F0,F1].
Similarly, this code:
g({a,_,_}=T) ->
{b,
[_,_] = [T,none],
x}.
would be rewritten to:
g({a,Tmp1,Tmp2}=T) ->
Tmp3 = {a,Tmp1,Tmp2},
{b,
[Tmp3,none],
x}.
where the tuple is rebuilt instead of using the T variable.
Rewrite case_opt/3 to be more careful while optimizing.
Diffstat (limited to 'lib/compiler/test/core_fold_SUITE.erl')
-rw-r--r-- | lib/compiler/test/core_fold_SUITE.erl | 31 |
1 files changed, 29 insertions, 2 deletions
diff --git a/lib/compiler/test/core_fold_SUITE.erl b/lib/compiler/test/core_fold_SUITE.erl index bca8afb1b0..b45874433c 100644 --- a/lib/compiler/test/core_fold_SUITE.erl +++ b/lib/compiler/test/core_fold_SUITE.erl @@ -23,7 +23,8 @@ t_element/1,setelement/1,t_length/1,append/1,t_apply/1,bifs/1, eq/1,nested_call_in_case/1,guard_try_catch/1,coverage/1, unused_multiple_values_error/1,unused_multiple_values/1, - multiple_aliases/1,redundant_boolean_clauses/1,mixed_matching_clauses/1]). + multiple_aliases/1,redundant_boolean_clauses/1, + mixed_matching_clauses/1,unnecessary_building/1]). -export([foo/0,foo/1,foo/2,foo/3]). @@ -40,7 +41,8 @@ groups() -> [t_element,setelement,t_length,append,t_apply,bifs, eq,nested_call_in_case,guard_try_catch,coverage, unused_multiple_values_error,unused_multiple_values, - multiple_aliases,redundant_boolean_clauses,mixed_matching_clauses]}]. + multiple_aliases,redundant_boolean_clauses, + mixed_matching_clauses,unnecessary_building]}]. init_per_suite(Config) -> @@ -403,4 +405,29 @@ mixed_matching_clauses(Config) when is_list(Config) -> end, ok. +unnecessary_building(Config) when is_list(Config) -> + Term1 = do_unnecessary_building_1(test_lib:id(a)), + [{a,a},{a,a}] = Term1, + 7 = erts_debug:size(Term1), + + %% The Input term should not be rebuilt (thus, it should + %% only be counted once in the size of the combined term). + Input = test_lib:id({a,b,c}), + Term2 = test_lib:id(do_unnecessary_building_2(Input)), + {b,[{a,b,c},none],x} = Term2, + 4+4+4+2 = erts_debug:size([Term2|Input]), + + ok. + +do_unnecessary_building_1(S) -> + %% The tuple must only be built once. + F0 = F1 = {S,S}, + [F0,F1]. + +do_unnecessary_building_2({a,_,_}=T) -> + %% The T term should not be rebuilt. + {b, + [_,_] = [T,none], + x}. + id(I) -> I. |