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authorBjörn Gustavsson <[email protected]>2015-04-26 07:12:26 +0200
committerBjörn Gustavsson <[email protected]>2015-04-29 12:25:06 +0200
commitc64199f4fce6c47323014b29623f78d0b3aad24f (patch)
tree3d28cb822a3c105e4ced0c3c4ced9aea6b058ca4
parent31779e0772006d822bb35b3f3fe0f0623d021aff (diff)
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beam_asm: Speed up encoding of large numbers
The misc_SUITE:integer_encoding/1 test case is annoyingly slow. Rewrite the encoding of integers in beam_asm to use the binary:encode_unsigned/1 BIF. Also tweak the test case itself. Scale the down the maximum size of the numbers being generated, but also add test of numbers around boundaries of power of two (which are the numbers most likely to expose bugs in the encoding).
-rw-r--r--lib/compiler/src/beam_asm.erl44
-rw-r--r--lib/compiler/test/misc_SUITE.erl20
2 files changed, 30 insertions, 34 deletions
diff --git a/lib/compiler/src/beam_asm.erl b/lib/compiler/src/beam_asm.erl
index 084686def7..73694b96ce 100644
--- a/lib/compiler/src/beam_asm.erl
+++ b/lib/compiler/src/beam_asm.erl
@@ -431,45 +431,35 @@ encode_alloc_list_1([], Dict, Acc) ->
{iolist_to_binary(Acc),Dict}.
encode(Tag, N) when N < 0 ->
- encode1(Tag, negative_to_bytes(N, []));
+ encode1(Tag, negative_to_bytes(N));
encode(Tag, N) when N < 16 ->
(N bsl 4) bor Tag;
encode(Tag, N) when N < 16#800 ->
[((N bsr 3) band 2#11100000) bor Tag bor 2#00001000, N band 16#ff];
encode(Tag, N) ->
- encode1(Tag, to_bytes(N, [])).
+ encode1(Tag, to_bytes(N)).
encode1(Tag, Bytes) ->
- case length(Bytes) of
+ case iolist_size(Bytes) of
Num when 2 =< Num, Num =< 8 ->
[((Num-2) bsl 5) bor 2#00011000 bor Tag| Bytes];
Num when 8 < Num ->
[2#11111000 bor Tag, encode(?tag_u, Num-9)| Bytes]
end.
-
-to_bytes(N0, Acc) ->
- Bits = 3*128,
- case N0 bsr Bits of
- 0 ->
- to_bytes_1(N0, Acc);
- N ->
- to_bytes(N, binary_to_list(<<N0:Bits>>) ++ Acc)
- end.
-
-to_bytes_1(0, [B|_]=Done) when B < 128 -> Done;
-to_bytes_1(N, Acc) -> to_bytes(N bsr 8, [N band 16#ff|Acc]).
-
-negative_to_bytes(N0, Acc) ->
- Bits = 3*128,
- case N0 bsr Bits of
- -1 ->
- negative_to_bytes_1(N0, Acc);
- N ->
- negative_to_bytes_1(N, binary_to_list(<<N0:Bits>>) ++ Acc)
+to_bytes(N) ->
+ Bin = binary:encode_unsigned(N),
+ case Bin of
+ <<0:1,_/bits>> -> Bin;
+ <<1:1,_/bits>> -> [0,Bin]
end.
-negative_to_bytes_1(-1, [B1,_B2|_]=Done) when B1 > 127 ->
- Done;
-negative_to_bytes_1(N, Acc) ->
- negative_to_bytes_1(N bsr 8, [N band 16#ff|Acc]).
+negative_to_bytes(N) when N >= -16#8000 ->
+ <<N:16>>;
+negative_to_bytes(N) ->
+ Bytes = byte_size(binary:encode_unsigned(-N)),
+ Bin = <<N:Bytes/unit:8>>,
+ case Bin of
+ <<0:1,_/bits>> -> [16#ff,Bin];
+ <<1:1,_/bits>> -> Bin
+ end.
diff --git a/lib/compiler/test/misc_SUITE.erl b/lib/compiler/test/misc_SUITE.erl
index 68a31f14d5..f3b92aad5b 100644
--- a/lib/compiler/test/misc_SUITE.erl
+++ b/lib/compiler/test/misc_SUITE.erl
@@ -338,8 +338,16 @@ integer_encoding_1(Config) ->
?line do_integer_encoding(-(id(1) bsl 10000), Src, Data),
?line do_integer_encoding(id(1) bsl 10000, Src, Data),
- ?line do_integer_encoding(2048, 0, Src, Data),
-
+ do_integer_encoding(1024, 0, Src, Data),
+ _ = [begin
+ B = 1 bsl I,
+ do_integer_encoding(-B-1, Src, Data),
+ do_integer_encoding(-B, Src, Data),
+ do_integer_encoding(-B+1, Src, Data),
+ do_integer_encoding(B-1, Src, Data),
+ do_integer_encoding(B, Src, Data),
+ do_integer_encoding(B+1, Src, Data)
+ end || I <- lists:seq(1, 128)],
io:put_chars(Src, "Last].\n\n"),
?line ok = file:close(Src),
io:put_chars(Data, "0].\n\n"),
@@ -372,11 +380,9 @@ do_integer_encoding(N, I0, Src, Data) ->
do_integer_encoding(I, Src, Data) ->
Str = integer_to_list(I),
- io:put_chars(Src, Str),
- io:put_chars(Src, ", \n"),
- io:put_chars(Data, Str),
- io:put_chars(Data, ", \n").
-
+ io:put_chars(Src, [Str,",\n"]),
+ io:put_chars(Data, [Str,",\n"]).
+
id(I) -> I.