[Lldb-commits] [lldb] Draft: [LLDB] Add scalar literal node (PR #147064)

[Ilia Kuklin via lldb-commits]

kuilpd wrote:

> say that values retain their width and signedness, but then get converted into the wider width using C-like rules. We already have this implemented inside the Scalar class (which wraps APInt), so this would be best in terms of code reuse, and it would produce few surprises to people used to C arithmetic. The Scalar class also supports floating point numbers (via APFloat), so this would automatically get us floating point support.

@labath 
I did an experimental implementation of this, basically relying on Scalar to do all arithmetics for me, including type conversions and promotions. It works, even when adding Scalar(APInt) and Scalar(APFloat), but a couple of things are weird:
1. Constant wrapping/unwrapping of Scalar(APInt). For literals, it goes: parse as APInt -> wrap to Scalar to create a node -> unwrap APInt to create ValueObjectSP -> wrap to Scalar to use arithmetic operation -> unwrap APInt to create ValueObjectSP. Not sure if it's a problem or not, but there's no functionality to store a Scalar in ValueObject.
2. Still not sure how to sensibly get a compiler type for a given number. I just did it by whatever size fits first. Also, it looks like bit size of APInt that comes from a ValueObject is not reliable, since even a variable of type `char` has an APInt with 32 bit size. The best I could come up with is to recreate APInt with the size taken from compiler type. After that, type promotion in Scalar works as expected.

https://github.com/llvm/llvm-project/pull/147064