llvm dev - Oct 2018 - InstCombineCasts and fastmath flags

Hi,
In llvm InstCombine pass, it is transforming FDiv(32bit for example)+FPTrunc
into FPTruncLHS+FPTruncRHS+FDiv(16bit)
This is in InstCombineCasts.cpp, InstCombiner::visitFPTrunc function.
During this transformation, it is also copying over the Fastmath flags (that
includes allowReciprocal flag) to FDiv(16bit).
There are some value ranges for denominator which might not overflow when
reciprocal is done on a 32 bit, but might overflow on a 16bit. In which case
allowReciprocal set on a 32 bit FDiv before transformation need not be
applicable to 16bit FDiv after transformation.
Shouldn't this llvm transformation not set allowReciprocal flag on FDiv(16)
when such transformation is done?

Thanks,
Srividya

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