[llvm-commits] [PATCH] Teach DAG combine to fold (trunc (fptoXi x)) to smaller (fptoXi x)

[Michael Liao]

Hi

Here is the patch teaching DAG combine to fold (trunc (fptoXi x)) to
smaller (fptoXi x). This trick is to tell backend the exact significant
bits to be preserved after FP conversion. As some backend has costy f32
to u32 conversion, f32 -> u32 -> u8 should be simplified as f32 -> u8
and mapped onto f32 -> i32 in code generation finally.

Thanks for your review.

Yours
- Michael

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