[llvm] Use DIExpression::foldConstantMath at the result of a Salvaged expression (PR #71721)

[Stephen Tozer via llvm-commits]

SLTozer wrote:

> @SLTozer Just pinging again in case you missed the updates,

Hi - just letting you know that I've been preoccupied by other work, but I'm looking at this now; the improvements in compile time LGTM. Outside of that my specific approval to land isn't necessary as long as the patches receive general approval, but otherwise I'll work my way through the patches that haven't yet got the green tick.

https://github.com/llvm/llvm-project/pull/71721