[erlang-patches] Use a set to store ref registers in beam_receive
Fredrik
fredrik@REDACTED
Wed Apr 10 10:02:05 CEST 2013
On 04/10/2013 12:19 AM, Anthony Ramine wrote:
> Hello,
>
> In some circumstances, as when inlining code, when some optimization passes are disabled or with hand-written but semantically correct Core Erlang or BEAM assembly, a fresh reference may be live in more than one register:
>
> ...
> {allocate_zero,2,2}.
> ...
> {call_ext,0,{extfunc,erlang,make_ref,0}}. % Ref in [x0]
> ...
> {move,{x,0},{y,0}}. % Ref in [x0,y0]
> {move,{y,1},{x,0}}. % Ref in [y0]
> ...
> {move,{y,0},{x,0}}. % Ref in [x0,y0]
> {move,{x,0},{y,1}}. % Ref in [x0,y0,y1]
> {label,5}.
> {loop_rec,{f,6},{x,0}}. % Ref in [y0,y1]
> ...
> {loop_rec_end,{f,5}}.
> {label,6}.
> {wait,{f,5}}.
> ...
>
> Pass beam_receive expects a single live register for the ref when it encounters the loop_rec instruction and crashes with the following reason:
>
> $ erlc t.S
> ...
> crash reason: {{case_clause,
> {'EXIT',
> {{case_clause,[{y,1},{y,0}]},
> [{beam_receive,opt_recv,5,
> [{file,"beam_receive.erl"},{line,154}]},
> ...]}}},
> ...}
>
> This patch teaches beam_receive how to use a set of registers instead of a single one when tracking fresh references, thus avoiding the crash.
>
> git fetch https://github.com/nox/otp.git fix-multiple-ref-regs
>
> https://github.com/nox/otp/compare/erlang:maint...fix-multiple-ref-regs
> https://github.com/nox/otp/compare/erlang:maint...fix-multiple-ref-regs.patch
>
> This is yet again something that I encountered while working on the file optimization branch file-receive-optim:
>
> https://gist.github.com/nox/2e33fe9a85e035caadda#file-t-codegen
>
> Regards,
>
Hello Anthony,
Fetched your branch. Currently in the review state and in 'pu' branch.
--
BR Fredrik Gustafsson
Erlang OTP Team
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