[llvm] [GlobalIsel] Canonicalize G_FCMP (PR #108891)

[Thorsten Schütt via llvm-commits]

tschuett wrote:

I remember there was a discussion on this topic. IR is well formed and it should work as expected.

const(i128)  = G_ZEXT G_CONSTANT i64

We have an i64 G_CONSTANT and zext it into the i128 const register.

https://github.com/llvm/llvm-project/pull/108891