compiler: Change some bifs to guard bifs in try/catch #9042
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CT Test ResultsNo tests were run for this PR. This is either because the build failed, or the PR is based on a branch without GH actions tests configured. Results for commit ad10c97 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 |
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lib/compiler/test/beam_ssa_check_SUITE_data/non_throwing_bifs.erl
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lib/compiler/src/beam_ssa_opt.erl
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| arity=A}=R0|Args0]}=I0|Is], | ||
| Acc) -> | ||
| %% Rewrite binary_to_atom/1 call to binary_to_atom/2. | ||
| {I1, Args1} = if {M, F, A} =:= {erlang, binary_to_atom, 1} -> |
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Should the same be done for binary_to_existing_atom?
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Yes, thanks for pointing out!
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What's the criteria to tell if a BIF can or cannot be optimised in this way? |
A BIF can be optimized this way if it's pure (i.e. does not change the state). If it's not pure, it's not always safe to remove the try/catch around it. Edit: Apparently I failed to count for |
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When put in a try, calling a guard bif with no side-effects is already
optimized to remove the try/catch. However, there are bifs with side-effects
that can be safely optimized in the same way in order to gain performance.
Example code:
try binary_to_atom(A, utf8)
catch _:_ -> []
end.
Before, SSA for the bif call after optimizations:
_6 = call (`erlang`:`binary_to_atom`/2), _0, `utf8`
_14 = succeeded:body _6
Now, SSA for the bif call after optimizations:
_6 = bif:binary_to_atom _0, `utf8`
_14 = succeeded:guard _6
Bifs that are optimized for try/catch in this change: `binary_to_atom/1`,
`binary_to_atom/2`, `binary_to_existing_atom/1`, `binary_to_existing_atom/2`,
`list_to_atom/1`, `list_to_existing_atom/1`.
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When put in a try, calling a guard bif with no side-effects and 6 other bifs ([PR-9042](erlang#9042)) are optimized to remove the try/catch. However, most pure bifs can be safely optimized in the same way in order to gain performance. This PR introduces a new internal instruction `call_pseudo_guard_bif` that enables the compiler to remove the try/catch around the bif. The instruction is designed to call the bif in the same way, but having more optimized error-handling in the runtime system. Example code: try float_to_list(A, utf8) catch _:_ -> error end. Before, assembly for the bif call after optimizations: {label,2}. {allocate,1,1}. {'try',{y,0},{f,3}}. {line,[{location,"zlc.erl",23}]}. {call_ext,1,{extfunc,erlang,float_to_list,1}}. {try_end,{y,0}}. {deallocate,1}. return. Now, assembly for the bif call after optimizations: {label,2}. {allocate,0,1}. {line,[{location,"zlc.erl",23}]}. {call_pseudo_guard_bif,1,{extfunc,erlang,float_to_list,1},{f,3}}. {deallocate,0}. return. Bifs that are optimized for try/catch in this change are listed in `pbif.tab`.
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This is a fix for [PR-9042](erlang#9042). `binary_to_atom/1` and `binary_to_existing_atom/1` now use the correct optimization. Tests for SSA in `non_throwing_bifs.erl` are fixed and added to the correct suite.
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When put in a try, calling a guard bif with no side-effects is already optimized to remove the try/catch. However, there are bifs with side-effects that can be safely optimized in the same way in order to gain performance.
Example code:
Before, SSA for the bif call after optimizations:
Now, SSA for the bif call after optimizations:
Bifs that are optimized for try/catch in this change:
binary_to_atom/1,binary_to_atom/2,binary_to_existing_atom/1,binary_to_existing_atom/2,list_to_atom/1,list_to_existing_atom/1.