Constfold constrained variants of operations fadd, fsub, fmul, fdiv,
frem, fma and fmuladd.
The change also sets up some means to support for removal of unused
constrained intrinsics. They are declared as accessing memory to model
interaction with floating point environment, so they were not removed,
as they have side effect. Now constrained intrinsics that have
"fpexcept.ignore" as exception behavior are removed if they have no uses.
As for intrinsics that have exception behavior other than "fpexcept.ignore",
they can be removed if it is known that they do not raise floating point
exceptions. It happens when doing constant folding, attributes of such
intrinsic are changed so that the intrinsic is not claimed as accessing
memory.
Differential Revision: https://reviews.llvm.org/D102673
Currently InstructionSimplify.cpp knows how to simplify floating point
instructions that have a NaN operand. It does not know how to handle the
matching constrained FP intrinsic.
This patch teaches it how to simplify so long as the exception handling
is not "fpexcept.strict".
Differential Revision: https://reviews.llvm.org/D103169
