[llvm] [SLP]Initial support for copyables in fmuladd intrinsic (PR #211245)

[Martin Storsjö via llvm-commits]

mstorsjo wrote:

This ends up triggers assertions in a lot of projects, when building for ARM.

Reduced reproducer:
```c
float a, b, e;
int c, d;
void f() { e = c * b + d + a; }
```
```console
$ clang -target armv7-linux-gnueabihf -c -O2 repro.c
clang: ../lib/IR/Instruction.cpp:673: bool llvm::Instruction::isFast() const
: Assertion `isa<FPMathOperator>(this) && "getting fast-math flag on invalid
 op"' failed.
```

https://github.com/llvm/llvm-project/pull/211245