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author | Björn Gustavsson <[email protected]> | 2018-01-22 16:27:33 +0100 |
---|---|---|
committer | Björn Gustavsson <[email protected]> | 2018-01-24 05:49:35 +0100 |
commit | ab6ac37e0c40331a2debd90f753ec2f4531e4701 (patch) | |
tree | 0dbe34e7630116c9874934d1f1013ba0571e1f8b /otp_patch_apply | |
parent | 25fa1aadc987f4c3abb8b39ae5fa090a9a103daa (diff) | |
download | otp-ab6ac37e0c40331a2debd90f753ec2f4531e4701.tar.gz otp-ab6ac37e0c40331a2debd90f753ec2f4531e4701.tar.bz2 otp-ab6ac37e0c40331a2debd90f753ec2f4531e4701.zip |
Correct unsafe optimizations in beam_block
When attempting to eliminate the move/2 instruction in the following
code:
{bif,self,{f,0},[],{x,0}}.
{move,{x,0},{x,1}}.
.
.
.
{put_tuple,2,{x,1}}.
{put,{atom,ok}}.
{put,{x,0}}.
beam_block would produce the following unsafe code:
{bif,self,{f,0},[],{x,1}}.
.
.
.
{put_tuple,2,{x,1}}.
{put,{atom,ok}}.
{put,{x,1}}.
It is unsafe because the tuple is self-referential.
The following code:
{put_list,{y,6},nil,{x,4}}.
{move,{x,4},{x,5}}.
{put_list,{y,1},{x,5},{x,5}}.
.
.
.
{put_tuple,2,{x,6}}.
{put,{x,4}}.
{put,{x,5}}.
would be incorrectly transformed to:
{put_list,{y,6},nil,{x,5}}.
{put_list,{y,1},{x,5},{x,5}}.
.
.
.
{put_tuple,2,{x,6}}.
{put,{x,5}}.
{put,{x,5}}.
(Both elements in the built tuple get the same value.)
Diffstat (limited to 'otp_patch_apply')
0 files changed, 0 insertions, 0 deletions