[llvm-dev] How to optimize store of constant arrays

[via llvm-dev]

Hi all, I have this problem:

I'm using LLVM's C++ API, mostly `IRBuilder<>` to generate code. Some of 
the generated code is just storing constant data to a location provided as 
a function argument. Something like 
`ir_builder.CreateStore(get_default_data(), ptrValue)` where 
`get_default_data()` may return a `ConstantArray` of `i8` and `ptrValue` 
is a function argument. Looking at the generated assembly, it seems 
inefficient, it generates a separate instruction for storing each byte 
relative to the pointer. Each instruction takes several bytes, and I am 
trying to optimize for code size.

The Q: What should I do to make the generated code more size-efficient 
(think `-Os`)?

Current ideas, which may not include the best answer:
- Store the data as-is in the IR, and use the `MemCpyInst` instead of the 
store when `get_default_data()` returns something big?
- Add a custom -- or any available built-in -- pass to the output to 
transform the store instns to memcpy when appropriate?

Thanks for any help,
Boldizsar
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