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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/genop.tab | |
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/genop.tab')
-rwxr-xr-x | lib/compiler/src/genop.tab | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/lib/compiler/src/genop.tab b/lib/compiler/src/genop.tab index f35ae09fe7..8e34e3e291 100755 --- a/lib/compiler/src/genop.tab +++ b/lib/compiler/src/genop.tab @@ -573,3 +573,8 @@ BEAM_FORMAT_NUMBER=0 ## @doc Get the tail (or cdr) part of a list (a cons cell) from Source and ## put it into the register Tail. 163: get_tl/2 + +## @spec put_tuple2 Destination Elements +## @doc Build a tuple with the elements in the list Elements and put it +## put into register Destination. +164: put_tuple2/2 |