[NVPTX] Fix NaN + overflow semantics of f2ll/d2i (#159530)

Fix the NaN-handling semantics of various NVVM intrinsics converting
from fp types to integer types.

Previously in ConstantFolding, NaN inputs would be constant-folded to 0.
However, v9.0 of the PTX spec states that:

In float-to-integer conversions, depending upon conversion types, NaN
input results in following value:
 * Zero if source is not `.f64` and destination is not `.s64`, .`u64`.
* Otherwise `1 << (BitWidth(dst) - 1)` corresponding to the value of
`(MAXINT >> 1) + 1` for unsigned type or `MININT` for signed type.

Also, support for constant-folding +/-Inf and values which
overflow/underflow the integer output type has been added (they clamp to
min/max int).

Because of this NaN-handling semantic difference, we also need to
disable transforming several intrinsics to FPToSI/FPToUI, as the LLVM
intstruction will return poison, but the intrinsics have defined
behaviour for these edge-cases like NaN/Inf/overflow.

0 files changed, 0 insertions, 0 deletions