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authorMagnus Lång <[email protected]>2016-11-21 17:39:56 +0100
committerMagnus Lång <[email protected]>2017-03-06 18:18:22 +0100
commit3abba595d91506f32aba47ecc39e9b6b3a08f645 (patch)
tree8d03f48040f168af0ef7ec288192d2259d4fa6a2
parent0b27cf500e4904bde9c8e2d82d3a74e0a74b30d0 (diff)
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hipe_beam_to_icode: Omit redtest in some closures
This is useful to generate shorter code for closures generated by (fun F/A).
-rw-r--r--lib/hipe/icode/hipe_beam_to_icode.erl31
1 files changed, 20 insertions, 11 deletions
diff --git a/lib/hipe/icode/hipe_beam_to_icode.erl b/lib/hipe/icode/hipe_beam_to_icode.erl
index 100bc0b0e2..610578dfbc 100644
--- a/lib/hipe/icode/hipe_beam_to_icode.erl
+++ b/lib/hipe/icode/hipe_beam_to_icode.erl
@@ -148,7 +148,8 @@ trans_mfa_code(M,F,A, FunBeamCode, ClosureInfo) ->
{Code3,_Env3} = mk_debug_calltrace(MFA, Env1, Code2),
{Code3,_Env3} = {Code2,Env1}),
%% For stack optimization
- Leafness = leafness(Code3),
+ IsClosure = get_closure_info(MFA, ClosureInfo) =/= not_a_closure,
+ Leafness = leafness(Code3, IsClosure),
IsLeaf = is_leaf_code(Leafness),
Code4 =
[FunLbl |
@@ -156,7 +157,6 @@ trans_mfa_code(M,F,A, FunBeamCode, ClosureInfo) ->
false -> Code3;
true -> [mk_redtest()|Code3]
end],
- IsClosure = get_closure_info(MFA, ClosureInfo) =/= not_a_closure,
Code5 = hipe_icode:mk_icode(MFA, FunArgs, IsClosure, IsLeaf,
remove_dead_code(Code4),
hipe_gensym:var_range(icode),
@@ -173,12 +173,12 @@ trans_mfa_code(M,F,A, FunBeamCode, ClosureInfo) ->
mk_redtest() -> hipe_icode:mk_primop([], redtest, []).
-leafness(Is) -> % -> true, selfrec, or false
- leafness(Is, true).
+leafness(Is, IsClosure) -> % -> true, selfrec, closure, or false
+ leafness(Is, IsClosure, true).
-leafness([], Leafness) ->
+leafness([], _IsClosure, Leafness) ->
Leafness;
-leafness([I|Is], Leafness) ->
+leafness([I|Is], IsClosure, Leafness) ->
case I of
#icode_comment{} ->
%% BEAM self-tailcalls become gotos, but they leave
@@ -191,7 +191,7 @@ leafness([I|Is], Leafness) ->
'self_tail_recursive' -> selfrec; % call_only to selfrec
_ -> Leafness
end,
- leafness(Is, NewLeafness);
+ leafness(Is, IsClosure, NewLeafness);
#icode_call{} ->
case hipe_icode:call_type(I) of
'primop' ->
@@ -199,12 +199,12 @@ leafness([I|Is], Leafness) ->
call_fun -> false; % Calls closure
enter_fun -> false; % Calls closure
#apply_N{} -> false;
- _ -> leafness(Is, Leafness) % Other primop calls are ok
+ _ -> leafness(Is, IsClosure, Leafness) % Other primop calls are ok
end;
T when T =:= 'local' orelse T =:= 'remote' ->
{M,F,A} = hipe_icode:call_fun(I),
case erlang:is_builtin(M, F, A) of
- true -> leafness(Is, Leafness);
+ true -> leafness(Is, IsClosure, Leafness);
false -> false
end
end;
@@ -223,11 +223,12 @@ leafness([I|Is], Leafness) ->
T when T =:= 'local' orelse T =:= 'remote' ->
{M,F,A} = hipe_icode:enter_fun(I),
case erlang:is_builtin(M, F, A) of
- true -> leafness(Is, Leafness);
+ true -> leafness(Is, IsClosure, Leafness);
+ _ when IsClosure -> leafness(Is, IsClosure, closure);
_ -> false
end
end;
- _ -> leafness(Is, Leafness)
+ _ -> leafness(Is, IsClosure, Leafness)
end.
%% XXX: this old stuff is passed around but essentially unused
@@ -235,12 +236,20 @@ is_leaf_code(Leafness) ->
case Leafness of
true -> true;
selfrec -> true;
+ closure -> false;
false -> false
end.
needs_redtest(Leafness) ->
case Leafness of
true -> false;
+ %% A "leaf" closure may contain tailcalls to non-closures in addition to
+ %% what other leaves may contain. Omitting the redtest is useful to generate
+ %% shorter code for closures generated by (fun F/A), and is safe since
+ %% control flow cannot return to a "leaf" closure again without a reduction
+ %% being consumed. This is true since no function that can call a closure
+ %% will ever have its redtest omitted.
+ closure -> false;
selfrec -> true;
false -> true
end.