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authorBjörn Gustavsson <[email protected]>2017-12-17 19:22:47 +0100
committerBjörn Gustavsson <[email protected]>2018-01-10 11:39:31 +0100
commitcb6fc15c35c7e588604cb9ee767b79b5e9627d46 (patch)
tree2c249e9cfefeee5febca6e0e375a121b3ab10954
parent161e67441cca56419fea70edf3ea790aff0f7b32 (diff)
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beam_block: Improve optimization of allocate_zero instructions
Turn more allocate_zero instructions into allocate instructions.
-rw-r--r--lib/compiler/src/beam_block.erl69
1 files changed, 40 insertions, 29 deletions
diff --git a/lib/compiler/src/beam_block.erl b/lib/compiler/src/beam_block.erl
index fe1ce6f60b..570fc05ae5 100644
--- a/lib/compiler/src/beam_block.erl
+++ b/lib/compiler/src/beam_block.erl
@@ -23,7 +23,7 @@
-module(beam_block).
-export([module/2]).
--import(lists, [reverse/1,reverse/2,foldl/3,member/2]).
+-import(lists, [reverse/1,reverse/2,member/2]).
-spec module(beam_utils:module_code(), [compile:option()]) ->
{'ok',beam_utils:module_code()}.
@@ -41,7 +41,8 @@ function({function,Name,Arity,CLabel,Is0}) ->
Is4 = move_allocates(Is3),
Is5 = beam_utils:live_opt(Is4),
Is6 = opt_blocks(Is5),
- Is = beam_utils:delete_live_annos(Is6),
+ Is7 = beam_utils:delete_live_annos(Is6),
+ Is = opt_allocs(Is7),
%% Done.
{function,Name,Arity,CLabel,Is}
@@ -143,10 +144,9 @@ opt_blocks([I|Is]) ->
opt_blocks([]) -> [].
opt_block(Is0) ->
- Is = find_fixpoint(fun(Is) ->
- opt_tuple_element(opt(Is))
- end, Is0),
- opt_alloc(Is).
+ find_fixpoint(fun(Is) ->
+ opt_tuple_element(opt(Is))
+ end, Is0).
find_fixpoint(OptFun, Is0) ->
case OptFun(Is0) of
@@ -411,31 +411,47 @@ eliminate_use_of_from_reg([I]=Is, From, _To, Acc) ->
no
end.
+%% opt_allocs(Instructions) -> Instructions. Optimize allocate
+%% instructions inside blocks. If safe, replace an allocate_zero
+%% instruction with the slightly cheaper allocate instruction.
+
+opt_allocs(Is) ->
+ D = beam_utils:index_labels(Is),
+ opt_allocs_1(Is, D).
+
+opt_allocs_1([{block,Bl0}|Is], D) ->
+ Bl = opt_alloc(Bl0, {D,Is}),
+ [{block,Bl}|opt_allocs_1(Is, D)];
+opt_allocs_1([I|Is], D) ->
+ [I|opt_allocs_1(Is, D)];
+opt_allocs_1([], _) -> [].
+
%% opt_alloc(Instructions) -> Instructions'
%% Optimises all allocate instructions.
opt_alloc([{set,[],[],{alloc,Live0,Info0}},
- {set,[],[],{alloc,Live,Info}}|Is]) ->
+ {set,[],[],{alloc,Live,Info}}|Is], D) ->
Live = Live0, %Assertion.
Alloc = combine_alloc(Info0, Info),
I = {set,[],[],{alloc,Live,Alloc}},
- opt_alloc([I|Is]);
-opt_alloc([{set,[],[],{alloc,R,{_,Ns,Nh,[]}}}|Is]) ->
- [{set,[],[],opt_alloc(Is, Ns, Nh, R)}|Is];
-opt_alloc([I|Is]) -> [I|opt_alloc(Is)];
-opt_alloc([]) -> [].
+ opt_alloc([I|Is], D);
+opt_alloc([{set,[],[],{alloc,R,{_,Ns,Nh,[]}}}|Is], D) ->
+ [{set,[],[],opt_alloc(Is, D, Ns, Nh, R)}|Is];
+opt_alloc([I|Is], D) -> [I|opt_alloc(Is, D)];
+opt_alloc([], _) -> [].
combine_alloc({_,Ns,Nh1,Init}, {_,nostack,Nh2,[]}) ->
{zero,Ns,beam_utils:combine_heap_needs(Nh1, Nh2),Init}.
-
+
%% opt_alloc(Instructions, FrameSize, HeapNeed, LivingRegs) -> [Instr]
%% Generates the optimal sequence of instructions for
%% allocating and initalizing the stack frame and needed heap.
-opt_alloc(_Is, nostack, Nh, LivingRegs) ->
+opt_alloc(_Is, _D, nostack, Nh, LivingRegs) ->
{alloc,LivingRegs,{nozero,nostack,Nh,[]}};
-opt_alloc(Is, Ns, Nh, LivingRegs) ->
- InitRegs = init_yreg(Is, 0),
+opt_alloc(Bl, {D,OuterIs}, Ns, Nh, LivingRegs) ->
+ Is = [{block,Bl}|OuterIs],
+ InitRegs = init_yregs(Ns, Is, D),
case count_ones(InitRegs) of
N when N*2 > Ns ->
{alloc,LivingRegs,{nozero,Ns,Nh,gen_init(Ns, InitRegs)}};
@@ -451,19 +467,14 @@ gen_init(Fs, Regs, Y, Acc) when Regs band 1 =:= 0 ->
gen_init(Fs, Regs, Y, Acc) ->
gen_init(Fs, Regs bsr 1, Y+1, Acc).
-%% init_yreg(Instructions, RegSet) -> RegSetInitialized
-%% Calculate the set of initialized y registers.
-
-init_yreg([{set,_,_,{bif,_,_}}|_], Reg) -> Reg;
-init_yreg([{set,_,_,{alloc,_,{gc_bif,_,_}}}|_], Reg) -> Reg;
-init_yreg([{set,_,_,{alloc,_,{put_map,_,_}}}|_], Reg) -> Reg;
-init_yreg([{set,Ds,_,_}|Is], Reg) -> init_yreg(Is, add_yregs(Ds, Reg));
-init_yreg(_Is, Reg) -> Reg.
-
-add_yregs(Ys, Reg) -> foldl(fun(Y, R0) -> add_yreg(Y, R0) end, Reg, Ys).
-
-add_yreg({y,Y}, Reg) -> Reg bor (1 bsl Y);
-add_yreg(_, Reg) -> Reg.
+init_yregs(Y, Is, D) when Y >= 0 ->
+ case beam_utils:is_killed({y,Y}, Is, D) of
+ true ->
+ (1 bsl Y) bor init_yregs(Y-1, Is, D);
+ false ->
+ init_yregs(Y-1, Is, D)
+ end;
+init_yregs(_, _, _) -> 0.
count_ones(Bits) -> count_ones(Bits, 0).
count_ones(0, Acc) -> Acc;