[PATCH] D119301: [AArch64][ARM] add -Wunaligned-access only for clang

Wed Feb 9 14:55:49 PST 2022

ychen added a comment.

In D119301#3309253 <https://reviews.llvm.org/D119301#3309253>, @ychen wrote:

> In D119301#3309140 <https://reviews.llvm.org/D119301#3309140>, @lenary wrote:
>
>> I don't fully understand the reasoning for the patch, and you haven't really explained it. I think what you are saying is that the `IsAux` argument to `getTargetFeatures` should be considered because it's `true` for offloading to another compiler, but I don't understand why we think the offload compiler is not clang-compatible, as the features added in `getAArch64TargetFeatures` and `getARMTargetFeatures` (and passed to the offloaded compiler) use the LLVM-specific internal names. I would like you to explain this further, and to document what `IsAux` implies in the code.
>
> Apologies for the lack of explanation. My point is that `getAArch64TargetFeatures` / `getARMTargetFeatures` should only get the TargetFeatures, not adding compiler flags as a side effect, which belongs to clang's job construction. This makes code reuse harder.
>
>> That all said code given here is not equivalent to the feature as originally landed, because you've only re-added the `-Wunaligned-access` flag for the AArch64 target - please make the same addition in `Clang::AddARMTargetArgs` as we want the warning on both. I think this also makes `CmdArgs` unused in both `aarch64::getAArch64TargetFeatures` and `arm::getARMTargetFeatures` as I think that you don't actually want us adding to `CmdArgs` in those functions (again, I hope the full reasoning behind this will be explained when you explain why the whole patch is necessary).
>
> Will do the same thing for `Clang::AddARMTargetArgs`. Thanks. I've tested this patch but not sure why the original test still passing without a `Clang::AddARMTargetArgs` change.

NVM. I see why: there were no driver tests. I'll add those.

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https://reviews.llvm.org/D119301