[PATCH] D29925: Implement intrinsic mangling for literal struct types.Fixes PR 31921

[Daniel Berlin via llvm-commits]

(Obviously they don't have to be literals, you can concot all sorts of sad
recursions where it's broken just with pointer, function, array, and struct
type involved)


On Tue, Feb 14, 2017 at 5:07 PM, Daniel Berlin via Phabricator <
reviews at reviews.llvm.org> wrote:

> dberlin added inline comments.
>
>
> ================
> Comment at: lib/IR/AutoUpgrade.cpp:492-493
>    }
> +  // Remangle our intrinsic since we upgrade the mangling
> +  auto Result = llvm::Intrinsic::remangleIntrinsicFunction(F);
> +  if (Result != None) {
> ----------------
> chandlerc wrote:
> > Scan the types to see if any are pointers to structs before doing this?
> Unfortunately, that won't work.
> In fact, that was my original workaround in predicateinfo that broke.
> There are two problems:
>
> 1. ssa_copy is anytype, so it can take a literal struct directly, which
> will still hit the assert.
>
> But hey, we could special case that one.
>
> There's a much worse problem though:
> 2. The mangling is recursive over array types, struct type, and function
> arguments/return types, so it's not enough to identify pointers to structs.
> They can be embedded *anywhere*.
>
> So, for example, a pointer to a function type that takes a literal struct
> as an argument would still hit the old assert (and still be changed in
> mangling)
> Or a pointer to function that has a return type of an array of pointers to
> functions that take literal structs ...
> ;(
>
>
> Essentially, the only way to avoid this check is either:
>
> A. We try to name match all the broken intrinsics and add any we missed
> over time.
> B. We give up and just use it like it is.
>
> I am happy to do A if we are concerned about the compile time cost
>
>
> https://reviews.llvm.org/D29925
>
>
>
>
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