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cdisselkoen / llvm-ir

LLVM IR in natural Rust data structures
MIT License
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Feature: Type sizes #31

Open langston-barrett opened 1 year ago

langston-barrett commented 1 year ago

I have an analysis that could make use of information about the sizes of types, in particular, what LLVM calls DataLayout::getTypeAllocSize. LLVM has a whole variety of methods that calculate different sorts of sizes for various types, it looks to me like they're all fundamentally based on DataLayout::getTypeSizeInBits.

cdisselkoen commented 1 year ago

LLVM does have a lot of methods (for this and other things) but unfortunately only a subset of them are exposed in the LLVM C API, which is what all Rust bindings are based off of. As a practical matter, we (llvm-ir) can't really take advantage of any LLVM APIs that don't exist in our dependency llvm-sys. You sound like you're familiar with the LLVM methods you're looking for; is LLVMSizeOf() something we could use to get sizes of types?

langston-barrett commented 1 year ago

LLVM does have a lot of methods (for this and other things) but unfortunately only a subset of them are exposed in the LLVM C API, which is what all Rust bindings are based off of. As a practical matter, we (llvm-ir) can't really take advantage of any LLVM APIs that don't exist in our dependency llvm-sys.

Ah, I was picturing llvm-ir reimplementing these methods, rather than, say, calling the LLVM method and storing the result alongside the type (which could take up a lot of space).

You sound like you're familiar with the LLVM methods you're looking for; is LLVMSizeOf() something we could use to get sizes of types?

Unfortunately, I'm only familiar with the C++ interface...