[clang] [llvm] [Driver] Default -msmall-data-limit= to 0 and clean up code (PR #83093)

[Michael Maitland via cfe-commits]

michaelmaitland wrote:

Adding a data point here: changing the small data limit to 0 is causing significant regressions on dhrystone, spec2006, spec2017, and geekbench5 on the sifive-x280 and sifive-p470.

Separate from this data point, a default of 8 bytes may be justified because most scalar primitives are 8 bytes or smaller on most architectures (boolean, char, int, unsigned, long, float, double, half). Data larger than this is likely something like arrays or structs.

https://github.com/llvm/llvm-project/pull/83093