support inline asm

[dvc94ch]

Useful to run tests for unsafe code with miri

[bjorn3]

https://internals.rust-lang.org/t/should-we-ever-stabilize-inline-assembly/11211/125

https://github.com/CraneStation/cranelift/issues/444#issuecomment-531574394

tl;dr: inline asm is hard.

[dvc94ch]

Wouldn't telling llvm to jit the inline asm somehow work? That shouldn't require the inline asm to be stabilized or reimplementing it in cranelift.

Alternatively a way to use an external assembler and jitting a binary blob would also work for me.

[bjorn3]

Wouldn't telling llvm to jit the inline asm somehow work? That shouldn't require the inline asm to be stabilized or reimplementing it in cranelift.

For miri: that would require FFI support in miri.

For cg_clif (my cranelift based codegen backend): cg_clif doesnt have any dependency on LLVM, which I want to keep that way.

[dvc94ch]

I see, so it's a duplicate of #11. Thanks.