[PATCH] D84044: [AArch64][SVE] Add missing unwind info for SVE registers.

[Sander de Smalen via Phabricator via llvm-commits]

sdesmalen added a comment.

In D84044#2172957 <https://reviews.llvm.org/D84044#2172957>, @efriedma wrote:

> > No changes are needed in Clang to support this AFAIK.
>
> (I meant loosely a change to clang and/or LLVM.)
>
> Consider the following testcase:
>
>   #include <arm_sve.h>
>   void g1(svuint8_t);
>   void g2(svuint8_t);
>   struct Z { svuint8_t *x; ~Z() { g2(*x); } };
>   svuint8_t f(svuint8_t a, svuint8_t b) {
>     Z z{&a};
>     g1(b);
>     return b;
>   }
>
>
> If unwind doesn't preserve SVE registers, we need a spill here.  clang currently doesn't generate one at -O2.


Yes, great spot! The caller should assume that all SVE registers are clobbered by the unwinder if the function _may_ throw an exception. I think I'll create a separate patch to fix this, as it's not necessarily something to do with how LLVM emits the unwind info, but rather a bug where the caller doesn't honour the right CC.


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