[RFC] Syncing Asm Goto with Outputs with GCC

[nickdesaulniers]

I’ve been working on this for a while now; I think I’ve come to the same conclusion as @rnk did years ago that a new landingpad-like instruction would be helpful.

[RFC] ASM Goto With Output Constraints

Generally, I’d prefer if we didn’t keep designing new features that assume the programmer knows what they’re doing. Personally, I had been considering reworking LLVM’s Windows EH representation to eliminate the catchswith instruction, which just exists to multiplex invoke unwind edges to multiple catch blocks. Instead, we’d use callbr, and I had been assuming it would have the normal behavior of producing the return value only along the normal path. Do you think landingpad offers alternative in…

Via lots of iteration, I think I now have this all coded up and working. I did write up an RFC to accompany the patches. I’m going to spend a little more time polishing the series, then will publish the patches and RFC soon.