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author | Björn Gustavsson <[email protected]> | 2018-09-01 10:57:33 +0200 |
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committer | Björn Gustavsson <[email protected]> | 2018-09-03 10:47:24 +0200 |
commit | 47a2ff39ac75c69b41f90f05a63fd9a2e6c0b36a (patch) | |
tree | f6ac446058b62541b7ec14dfc28a21a06c5cbc7e /lib/compiler/src/beam_ssa_pre_codegen.erl | |
parent | 31e7b5ab0b72acbbca649b99ade82bba145cc390 (diff) | |
download | otp-47a2ff39ac75c69b41f90f05a63fd9a2e6c0b36a.tar.gz otp-47a2ff39ac75c69b41f90f05a63fd9a2e6c0b36a.tar.bz2 otp-47a2ff39ac75c69b41f90f05a63fd9a2e6c0b36a.zip |
Introduce a put_tuple2 instruction
Sometimes when building a tuple, there is no way to avoid an
extra `move` instruction. Consider this code:
make_tuple(A) -> {ok,A}.
The corresponding BEAM code looks like this:
{test_heap,3,1}.
{put_tuple,2,{x,1}}.
{put,{atom,ok}}.
{put,{x,0}}.
{move,{x,1},{x,0}}.
return.
To avoid overwriting the source register `{x,0}`, a `move`
instruction is necessary.
The problem doesn't exist when building a list:
%% build_list(A) -> [A].
{test_heap,2,1}.
{put_list,{x,0},nil,{x,0}}.
return.
Introduce a new `put_tuple2` instruction that builds a tuple in a
single instruction, so that the `move` instruction can be eliminated:
%% make_tuple(A) -> {ok,A}.
{test_heap,3,1}.
{put_tuple2,{x,0},{list,[{atom,ok},{x,0}]}}.
return.
Note that the BEAM loader already combines `put_tuple` and `put`
instructions into an internal instruction similar to `put_tuple2`.
Therefore the introduction of the new instruction will not speed up
execution of tuple building itself, but it will be less work for
the loader to load the new instruction.
Diffstat (limited to 'lib/compiler/src/beam_ssa_pre_codegen.erl')
-rw-r--r-- | lib/compiler/src/beam_ssa_pre_codegen.erl | 23 |
1 files changed, 13 insertions, 10 deletions
diff --git a/lib/compiler/src/beam_ssa_pre_codegen.erl b/lib/compiler/src/beam_ssa_pre_codegen.erl index bbc3739eb5..54aa2efaf6 100644 --- a/lib/compiler/src/beam_ssa_pre_codegen.erl +++ b/lib/compiler/src/beam_ssa_pre_codegen.erl @@ -79,8 +79,9 @@ {'ok',beam_ssa:b_module()}. module(#b_module{body=Fs0}=Module, Opts) -> + FixTuples = proplists:get_bool(no_put_tuple2, Opts), ExtraAnnos = proplists:get_bool(dprecg, Opts), - Ps = passes(ExtraAnnos), + Ps = passes(FixTuples, ExtraAnnos), Fs = functions(Fs0, Ps), {ok,Module#b_module{body=Fs}}. @@ -113,13 +114,16 @@ functions([], _Ps) -> []. }). -define(PASS(N), {N,fun N/1}). -passes(ExtraAnnos) -> +passes(FixTuples, ExtraAnnos) -> Ps = [?PASS(assert_no_critical_edges), %% Preliminaries. ?PASS(fix_bs), ?PASS(sanitize), - ?PASS(fix_tuples), + case FixTuples of + false -> ignore; + true -> ?PASS(fix_tuples) + end, ?PASS(place_frames), ?PASS(fix_receives), @@ -151,10 +155,7 @@ passes(ExtraAnnos) -> ?PASS(fix_aliased_regs), ?PASS(frame_size), ?PASS(turn_yregs)], - case ExtraAnnos of - false -> [P || P <- Ps, P =/= ignore]; - true -> Ps - end. + [P || P <- Ps, P =/= ignore]. function(#b_function{anno=Anno,args=Args,bs=Blocks0,cnt=Count0}=F0, Ps) -> try @@ -693,9 +694,11 @@ prune_phi(#b_set{args=Args0}=Phi, Reachable) -> %%% %% fix_tuples(St0) -> St. -%% We must split tuple creation into two instruction to mirror the -%% the way tuples are created in BEAM. Each put_tuple instruction is -%% split into put_tuple_arity followed by put_tuple_elements. +%% If compatibility with a previous version of Erlang has been +%% requested, tuple creation must be split into two instruction to +%% mirror the the way tuples are created in BEAM prior to OTP 22. +%% Each put_tuple instruction is split into put_tuple_arity followed +%% by put_tuple_elements. fix_tuples(#st{ssa=Blocks0,cnt=Count0}=St) -> F = fun (#b_set{op=put_tuple,args=Args}=Put, C0) -> |