[PATCH] D152766: AMDGPU: Use correct lowering for llvm.log2.f32

Thu Jun 22 01:45:12 PDT 2023

rampitec added inline comments.

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Comment at: llvm/docs/AMDGPUUsage.rst:963
+                                             half). Not implemented for double. Hardware provides
+                                             1ULP accuracy for float, and 0.51ULP for half. Float
+                                             instruction does not natively support denormal
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rampitec wrote:
> arsenm wrote:
> > rampitec wrote:
> > > Typo 0.51ULP?
> > That's what the last 3 public ISA docs say
> For what I know this does not make any sense. Someones finger must be mistyped. @b-sumner can you comment please?
I.e. I understand 0.5ULP. This is half of a bit, when you do not known how to round it: up or down. But what is 1/100 of a bit? Is that like your computation is 100 bits more accurate, but you do not know how to round it?

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D152766/new/

https://reviews.llvm.org/D152766