[llvm] [RISCV][CostModel] Estimate cost of llvm.vector.reduce.fmaximum/fminimum (PR #80697)
Craig Topper via llvm-commits
llvm-commits at lists.llvm.org
Wed Mar 13 14:52:41 PDT 2024
topperc wrote:
> Not by any means an FP expert, but isn't there a massively better lowering available here?
>
> Written as a vector pseudo language:
>
> ```
> masknan = foreach lane in input, isnan(lane)
> masknegzero = foreach lane in input, isnegzero(lane)
> scalar = reduce.fmin(input)
> if anyof(masknan)
> scalar = v[clz(masknan);
> if scalar == 0.0 and anyof(masknegzero)
> scalar = 0.0
> ```
>
> If so, I'd be tempted to fix that before worrying about the costing in TTI.
negzero shouldn't be an issue. I think our instructions respect the order of -0.0 and 0.0.
https://github.com/llvm/llvm-project/pull/80697
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