Scala.js: Emit js.NewArray IR nodes when possible.
#22446
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Although there is a *correct* implementation of `sr.Arrays.newArray`, it is not efficient when creating 1-dimensional arrays. The JVM backend special-cases it to emit `newarray` bytecode instructions. We now also special-case it in the JS backend. In the Scala.js IR however, `js.NewArray` only accepts a single dimension. For multiple dimensions, the right thing to do is to emit a direct call to `jlr.Array.newInstance`.
smarter
approved these changes
Jan 27, 2025
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Does make sense backporting it to LTS, which doesn't update the Scala JS versions? |
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Probably. The LTS uses an older version of Scala.js that had builtin support for If you backport this one, you also need to backport #22797 . |
This was referenced Apr 3, 2025
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Although there is a correct implementation of
sr.Arrays.newArray, it is not efficient when creating 1-dimensional arrays. The JVM backend special-cases it to emitnewarraybytecode instructions.We now also special-case it in the JS backend. In the Scala.js IR however,
js.NewArrayonly accepts a single dimension. For multiple dimensions, the right thing to do is to emit a direct call tojlr.Array.newInstance.