sdesmalen added inline comments.
================
Comment at: clang/lib/Driver/ToolChains/Arch/AArch64.cpp:369
+ if (llvm::is_contained(Features, "+v8.6a")) {
+ if (!llvm::is_contained(Features, "-i8mm") &&
+ !llvm::is_contained(Features, "+noi8mm"))
----------------
fpetrogalli wrote:
> sdesmalen wrote:
> > Is this correct and/or necessary? I would expect LLVM to just handle
> > features in the order they're passed, and the architecture version is
> > always processed first, e.g. `-march=armv8.6-a+noi8mm` will always first
> > process `armv8.6a` before processing features like `noi8mm`.
> I was expecting that too, but in in this place the `+i8mm` is added after
> whatever the user have passed to -march, which means that without this extra
> check the user input `-mattr=armv8.6a+sve+noimm8` becomes broken because we
> are adding `-target-feature=+i8mm` after `-i8mm`. This behavior is guarded
> by a regression tests that starts failing if I don't use these extra checks.
> This was not needed in the original place were I added the functionality
> because the `+i8mm` was being added right after `+v8.6a` and before splitting
> up the `+sve+noi8mm`, so that the user input was the one (un)setting the
> feature.
As you said, we end up with a Feature list as follows:
parsing(-march=armv8.6-a+noi8mm)
=> Features = [ v8.6a ]
parsing(+noi8mm)
=> Features = [ v8.6a, -i8mm ]
Then going through the feature list again:
=> Features = [ v8.6a, -i8mm, +i8mm ]
^^^^^ ^^^^
\_____________/
adds +i8mm
To fix that, you can insert these features into the list straight after
"+v8.6a", instead of appending at the end of the Features list. Either that, or
calling `llvm::AArch64::getDefaultExtensions() +
llvm::AArch64::getExtensionFeatures()` in `getAArch64ArchFeaturesFromMarch`
like is done in `DecodeAArch64Mcpu`, which should do all this for free. That
seems like a more invasive change though that you shouldn't try to do in this
patch.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D83079/new/
https://reviews.llvm.org/D83079
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