diff options
Diffstat (limited to 'lib/compiler/src')
-rw-r--r-- | lib/compiler/src/beam_ssa_dead.erl | 59 |
1 files changed, 31 insertions, 28 deletions
diff --git a/lib/compiler/src/beam_ssa_dead.erl b/lib/compiler/src/beam_ssa_dead.erl index c20652580d..067d9a6741 100644 --- a/lib/compiler/src/beam_ssa_dead.erl +++ b/lib/compiler/src/beam_ssa_dead.erl @@ -135,7 +135,8 @@ shortcut_terminator(Last, _Is, _Bs, _St) -> Last. shortcut_switch([{Lit,L0}|T], Bool, Bs, St0) -> - St = St0#st{rel_op=normalize_op({bif,'=:='}, [Bool,Lit])}, + RelOp = {'=:=',Bool,Lit}, + St = St0#st{rel_op=RelOp}, #b_br{bool=#b_literal{val=true},succ=L} = shortcut(L0, bind_var(Bool, Lit, Bs), St#st{target=one_way}), [{Lit,L}|shortcut_switch(T, Bool, Bs, St0)]; @@ -388,41 +389,43 @@ eval_terminator(#b_switch{arg=Arg,fail=Fail,list=List}=Sw, Bs, St) -> %% Literal argument. Simplify to a `br`. beam_ssa:normalize(Sw#b_switch{arg=Val}); #b_var{} -> - case St of - #st{rel_op=none} -> - %% No previous relational operator is stored. - %% Give up. + %% Try optimizing the switch. + case eval_switch(List, Arg, St, Fail) of + none -> none; - #st{} -> - %% There is a previous relational operator stored. - %% Try optimizing the switch. - case eval_switch(List, Arg, St, Fail) of - none -> - none; - To when is_integer(To) -> - %% Either one of the values in the switch - %% matched a previous value in a '=:=' test, or - %% none of the values matched a previous test. - #b_br{bool=#b_literal{val=true},succ=To,fail=To} - end + To when is_integer(To) -> + %% Either one of the values in the switch + %% matched a previous value in a '=:=' test, or + %% none of the values matched a previous test. + #b_br{bool=#b_literal{val=true},succ=To,fail=To} end end; eval_terminator(#b_ret{}, _Bs, _St) -> none. -eval_switch([{Lit,Lbl}|T], Arg, St, Fail) -> - case eval_rel_op({bif,'=:='}, [Arg,Lit], St) of - none -> - %% This label could be reached. - eval_switch(T, Arg, St, none); - #b_literal{val=false} -> - %% This branch will never be taken. - eval_switch(T, Arg, St, Fail); - #b_literal{val=true} -> +eval_switch(List, Arg, #st{rel_op={_,Arg,_}=PrevOp}, Fail) -> + %% There is a previous relational operator testing the same variable. + %% Optimization may be possible. + eval_switch_1(List, Arg, PrevOp, Fail); +eval_switch(_, _, _, _) -> + %% There is either no previous relational operator, or it tests + %% a different variable. Nothing to optimize. + none. + +eval_switch_1([{Lit,Lbl}|T], Arg, PrevOp, Fail) -> + RelOp = {'=:=',Arg,Lit}, + case will_succeed(PrevOp, RelOp) of + yes -> %% Success. This branch will always be taken. - Lbl + Lbl; + no -> + %% This branch will never be taken. + eval_switch_1(T, Arg, PrevOp, Fail); + maybe -> + %% This label could be reached. + eval_switch_1(T, Arg, PrevOp, none) end; -eval_switch([], _Arg, _St, Fail) -> +eval_switch_1([], _Arg, _PrevOp, Fail) -> %% Fail is now either the failure label or 'none'. Fail. |