[llvm-dev] RFC: Strong GC References in LLVM

Andrew Trick via llvm-dev llvm-dev at lists.llvm.org
Fri Jul 15 17:25:13 PDT 2016

> On Jul 15, 2016, at 4:48 PM, Hal Finkel <hfinkel at anl.gov> wrote:
> Why? A decision was made to give pointers types, and we've decided to change that. It is not clear to me that the decision to allow implicit early exits was, in retrospect, optimal. I think it is completely healthy for the project to reevaluate these kinds of decisions. We now have many years of experience, bug reports, and we should have a good ability to evaluate the compile-time impact of a potential change.

Let me rephrase: It didn’t seem to me like the fundamental problem we were up against in this discussion, and it’s definitely very difficult to change given the burden it would place on intrinsics.

FWIW, for a long time I was a very strong proponent of explicit control flow because I like making it easy to reason about CFG transforms and code motion. But I gradually came around to realize it’s a legitimate design either way. In some ways it works well not to have a CFG edge for exits where it’s illegal to insert code. I think LLVM passes have also been biased toward algorithms that scale in the number of blocks.

That’s all I really have to say about it.

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