Cleanup handling of the denormal-fp-math attribute. Consolidate places
checking the allowed names in one place. Also begin migrating towards
the current IEEE-754's standard's preferred terminology of subnormal
This is in preparation for introducing FP type specific variants of
the denorm-fp-mode attribute. AMDGPU will switch to using this in
place of the current hacky use of subtarget features for the denormal
Introduce a new header for dealing with FP modes. The constrained
intrinsic classes define related enums that should also be moved into
this header for uses in other contexts.
The verifier could use a check to make sure the denorm-fp-mode
attribute is sane, but there currently isn't one.
There is a problem with this patch as is. The one place currently
checking this attribute in buildSqrtEstimateImpl (added by D42323)
oddly doesn't assume the ieee behavior if the attribute isn't
specified as I would expect. The question of why this behaves this way
needs to be resolved to proceed as tests fail due to assuming IEEE
behavior on undecorated functions.