[llvm] [X86][MC] Report error when the instruction length exceeds 15 bytes (PR #83708)

[Phoebe Wang via llvm-commits]

phoebewang wrote:

> > Does it crash too if you compile it to object file? https://godbolt.org/z/3aqd497xG
> > @phoebewang Yes, it crashes. @e-kud is asking if we could report the error earlier (before encoding)

We usually don't verify the inline asemble in codegen, because we assume user should be responsible for their mistakes in inline asemble.
But the thing is a bit complicated here. If user uses "m" constrain, they cannot forsee compiler will generate a SIB addressing or using x87 mode for it. Compiler need to take this responsibility to emit error or never generate SIB addressing in this case.

https://github.com/llvm/llvm-project/pull/83708