[llvm] [SystemZ] Remove getInliningThresholdMultiplier() override (PR #94612)

[Jonas Paulsson via llvm-commits]

JonPsson1 wrote:

I don't think we can just disable this without a replacement: I see regressions on imagick (9%) and perl (5%) and probably others as well...


https://github.com/llvm/llvm-project/pull/94612