compile.c: statically resolve swap instructions when possible - #18538
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byroot
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Aug 27, 2026
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| type == BIN(putobject) || | ||
| type == BIN(putspecialobject) || | ||
| type == BIN(putnil) || | ||
| type == BIN(putself) || | ||
| type == BIN(duphash) || | ||
| type == BIN(getinstancevariable) || | ||
| type == BIN(getlocal) |
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Would be worth analyzing some real world code to see if there's some more common cases.
If the two preceeding instructions are known not to be dependent
on the state of the stack, then we can eliminate the `swap` and inverse
the two previous instructions.
This mostly eliminate instruction in two cases:
```ruby
Object.new
```
```
0000 opt_getconstant_path <ic:0 Object> ( 1)[Li]
0002 putnil
0003 swap
0004 opt_new <calldata!mid:new, argc:0, ARGS_SIMPLE>, 11
```
And:
```ruby
{**@A, b: 2}
```
```
0000 getinstancevariable :@A, <is:0> ( 1)[Li]
0003 putspecialobject 1
0005 swap
0006 putobject :b
0008 putobject 2
0010 opt_send_without_block <calldata!mid:core#hash_merge_ptr, argc:3, ARGS_SIMPLE>
```
Co-Authored-By: John Hawthorn <john@hawthorn.email>
eregon
reviewed
Sep 8, 2026
| ruby/parser_test.rb | ||
| ruby/ripper_test.rb | ||
| ruby/ruby_parser_test.rb | ||
| ruby/parameters_signature_test.rb |
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This actually found that this PR causes 2 :line events on the second line for
return unless x
Foo.newSee https://bugs.ruby-lang.org/issues/22299
I'm aiming to remove all skips in ruby/prism#4223 so it's clear new skips should not be added but are actual regressions for :line events.
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Sorry about that, I'll have to dig into tracepoint to see if that's possible to fix, or if I have to revert that optimization.
byroot
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Sep 9, 2026
[Bug #22299] Followup: ruby#18538
byroot
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Sep 9, 2026
[Bug #22299] Followup: ruby#18538
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If the two preceeding instructions are known not to be dependent on the state of the stack, then we can eliminate the
swapand inverse the two previous instructions.This mostly eliminate instruction in two cases:
And: