When the math goes double and comes back single
Promote your f32 operands to f64 and the whole expression changes flavor. The arithmetic drops its s suffix and becomes the plain double forms, fmul and fadd and friends, while any constant arrives as a double through lfd instead of lfs. A single-precision value can step straight into a double op, no widening instruction required, because it is already exactly representable. The catch comes at the end. Hand back an f32 from double math and the result has to be rounded down with frsp first.
Take avg2(p, q), which averages two values in double precision and then narrows:
fadd f0, f1, f2 # double add: (double)p + (double)q
lfd f1, ... # load 0.5 as a *double* (lfd, not lfs)
fmul f1, f1, f0 # double multiply by 0.5
frsp f1, f1 # round the f64 result back to f32 for return
blr
Double math leaves fingerprints all over this. fadd and fmul with no s, an lfd rather than lfs for the constant, and that frsp at the close. The frsp is the giveaway for double-computed, single-returned code. Write the same thing in straight f32 and you would see fadds/fmuls/lfs with no frsp anywhere. So whenever a frsp shows up next to suffix-less ops, the original C cast its operands up to double.
Your target runs a different double-precision computation that still finishes on frsp. Read the suffix-less ops, the lfd constant, and that closing frsp, and you can locate where the cast to f64 happens and what the final narrowing does.
Your task
Write mix, taking two f32s, to reproduce the assembly above. Cast as needed so the arithmetic happens in f64 and is narrowed back on return.