Minimal support of floating-point operand bundles
This is a lite version of https://github.com/llvm/llvm-project/pull/109798,
where code changes are minimized to facilitate discussion about the
implementation. The motivations and ideas behind the new floating-point
operation support are described in that PR and in the discussion
https://discourse.llvm.org/t/rfc-change-of-strict-fp-operation-representation-in-ir/85021.
There are concerns that the proposed changes are too invasive and a new
approach is required to make the transition smoother.
This implementation is essentially a subset of PR109798, where
everything beyond the minimum is removed. It tries to build eventually
the same implementation as that PR but in different steps.
The patch does not attempt to modify the existing implementation based
on the constrained intrinsics. Instead it introduces a new one using
operand bundles. This new implementation initially has very limited
functionality, which latter will be extended and finally can replace the
existing one.
This PR introduces the notion of floating-point operation, this is an
intrinsic, that is listed in the file "FloatingPointOps.def". These have
two additional properties:
1. In the strict environment (a function with strictfp attribute) calls
to these operations acquire side effect, now it is read/write access
to inaccessible memory, just as constrained intrinsics do.
2. Calls to these operations may have floating-point operand bundles.
There are two kinds of such bundles, tagged with "fp.control" and
"fp.except", which are used to carry additional information about
control modes and exception handling. Initially the set of control
modes consists of rounding mode only.
The set of operations enlisted in "FloatingPointOps.def" and in
"ConstrainedOps.def" are completely independent, an intrinsic may be in
one list or in both. The set of floating-point operations is expected to
grow and finally all FP intrinsics will be available in the new
implementation. In this patch set of intrinsics in
"FloatingPointOps.def" is minimum necessary for tests.
