Fix bug in private-append transform #7207
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Fix a bug in the SSA-checker where it trashes the environment after matching a literal bitstring.
This change stops the compiler from generating invalid code when
bs_create_bin is given a literal <<>> as its first fragment. As the
type analyzer considers a literal <<>> an appendable bitstring, code
sequences such as:
_6 = bs_create_bin `append`, `[8,{segment,1}]`, `<<>>`, `all`
...
_14 = bs_create_bin `append`, `[8,{segment,1}]`, _6, `all`
would be rewritten to:
_6 = bs_create_bin `private_append`, `[8,{segment,1}]`, `<<>>`, `all`
...
_14 = bs_create_bin `private_append`, `[8,{segment,1}]`, _6, `all`
which is not legal, as private_append on a literal will crash the
runtime system.
By inserting a bs_init_writable in front of bs_create_bin instructions
with a literal <<>> as the first fragment, and then using the freshly
created writable binary instead of the literal, the code sequence
becomes valid:
_1 = bs_init_writable `256`
_6 = bs_create_bin `private_append`, `[8,{segment,1}]`, _1, `all`
...
_14 = bs_create_bin `private_append`, `[8,{segment,1}]`, _6, `all`
CT Test Results 2 files 296 suites 11m 39s ⏱️ Results for commit 5277d99. ♻️ This comment has been updated with latest results. To speed up review, make sure that you have read Contributing to Erlang/OTP and that all checks pass. See the TESTING and DEVELOPMENT HowTo guides for details about how to run test locally. Artifacts// Erlang/OTP Github Action Bot |
bjorng
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Thanks! Added to our daily builds. |
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