compile.c: deduplicate inline constant caches #13060
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✅ All Tests passed!✖️no tests failed ✔️61916 tests passed(1 flake) |
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If a method reference the same constant twice or more, it can use a single constant cache for all the instructions. ```ruby puts RubyVM::InstructionSequence.compile(<<~RUBY).disasm Foo::Bar + Foo::Bar + Bar + Bar RUBY ``` Before ``` == disasm: #<ISeq:<compiled>@<compiled>:1 (1,0)-(1,31)> 0000 opt_getconstant_path <ic:0 Foo::Bar> ( 1)[Li] 0002 opt_getconstant_path <ic:1 Foo::Bar> 0004 opt_plus <calldata!mid:+, argc:1, ARGS_SIMPLE>[CcCr] 0006 opt_getconstant_path <ic:2 Bar> 0008 opt_plus <calldata!mid:+, argc:1, ARGS_SIMPLE>[CcCr] 0010 opt_getconstant_path <ic:3 Bar> 0012 opt_plus <calldata!mid:+, argc:1, ARGS_SIMPLE>[CcCr] 0014 leave ``` After: ``` == disasm: #<ISeq:<compiled>@<compiled>:1 (1,0)-(1,31)> 0000 opt_getconstant_path <ic:0 Foo::Bar> ( 1)[Li] 0002 opt_getconstant_path <ic:0 Foo::Bar> 0004 opt_plus <calldata!mid:+, argc:1, ARGS_SIMPLE>[CcCr] 0006 opt_getconstant_path <ic:1 Bar> 0008 opt_plus <calldata!mid:+, argc:1, ARGS_SIMPLE>[CcCr] 0010 opt_getconstant_path <ic:1 Bar> 0012 opt_plus <calldata!mid:+, argc:1, ARGS_SIMPLE>[CcCr] 0014 leave ```
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Tested on Shopify's monolith. Before: After: So the gain is relatively modest (0.6%). But if we were to do the same for other types of caches, it might add up. I also tried to graph these with a scatter plot. |
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If a method reference the same constant twice or more, it can use a single constant cache for all the instructions.
Before
After: