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The following method call: ```ruby a(*nil) ``` A method call such as `a(*nil)` previously allocated an array, because it calls `nil.to_a`, but I have determined this array allocation is unnecessary. The instructions in this case are: ``` 0000 putself ( 1)[Li] 0001 putnil 0002 splatarray false 0004 opt_send_without_block <calldata!mid:a, argc:1, ARGS_SPLAT|FCALL> 0006 leave ``` The method call uses `ARGS_SPLAT` without `ARGS_SPLAT_MUT`, so the returned array doesn't need to be mutable. I believe all cases where `splatarray false` are used allow the returned object to be frozen, since the `false` means to not duplicate the array. The optimization in this case is to have `splatarray false` push a shared empty frozen array, instead of calling `nil.to_a` to return a newly allocated array. There is a slightly backwards incompatibility with this optimization, in that `nil.to_a` is not called. However, I believe the new behavior of `*nil` not calling `nil.to_a` is more consistent with how `**nil` does not call `nil.to_hash`. Also, so much Ruby code would break if `nil.to_a` returned something different from the empty hash, that it's difficult to imagine anyone actually doing that in real code, though we have a few tests/specs for that. I think it would be bad for consistency if `*nil` called `nil.to_a` in some cases and not others, so this changes other cases to not call `nil.to_a`: For `[*nil]`, this uses `splatarray true`, which now allocates a new array for a `nil` argument without calling `nil.to_a`. For `[1, *nil]`, this uses `concattoarray`, which now returns the first array if the second array is `nil`. This updates the allocation tests to check that the array allocations are avoided where possible. Implements [Feature #21047]
10 lines
124 B
YAML
10 lines
124 B
YAML
prelude: |
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def a = nil
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benchmark:
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to_i: |
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nil.to_i
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to_f: |
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nil.to_f
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splat: |
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a(*nil)
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loop_count: 100000
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