[SR-13871] "Fixed size array" codegen via unsafeBufferPointer is dramatically worse in 5.3 #56269
Labels
bug
A deviation from expected or documented behavior. Also: expected but undesirable behavior.
compiler
The Swift compiler in itself
performance
Additional Detail from JIRA
md5: 9b9937bfb81eafdddc433dcd972c423b
Issue Description:
https://swift.godbolt.org/z/KW81eE
The code generation for "testOptimization" in this example got dramatically worse sometime between 5.2 and 5.3. In 5.2 we see:
which is basically optimal, but in 5.3 we see the following instead:
This is probably not a Swift bug, but rather a break in the LLVM cost model, but it's worth tracking here because the performance and code size impact is severe.
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