[llvm] [DA] Fix overflows when calculating Delta in the Weak Zero SIV tests (PR #184997)

[Sjoerd Meijer via llvm-commits]

sjoerdmeijer wrote:

The change in itself looks good to me. 

But just an observation and a style question: it is the same change applied to 2 different functions `weakZeroSrcSIVtest` and `weakZeroDstSIVtest` that look very very similar. These two functions looks like a copy-paste job, with some minor differences in e.g. the Direction. This isn't a very good SW engineering practise, illustrated by the need to apply the same fix in different places. Would this be a good moment to refactor this code, and apply this fix in one place? What do you think?

https://github.com/llvm/llvm-project/pull/184997