The SVE ACLE doesn't allow arrays of sizeless types. At the moment
clang accepts the TU:
__SVInt8_t x[2];
but trying to code-generate it triggers the LLVM assertion:
llvm/lib/IR/Type.cpp:588: static llvm::ArrayType* llvm::ArrayType::get(llvm::Type*, uint64_t): Assertion `isValidElementType(ElementType) && "Invalid type for array element!"' failed.
This patch reports an appropriate error instead.
The rules are slightly more restrictive than for general incomplete types.
For example:
struct s;
typedef struct s arr[2];
is valid as far as it goes, whereas arrays of sizeless types are
invalid in all contexts. BuildArrayType therefore needs a specific
check for isSizelessType in addition to the usual handling of
incomplete types.
Differential Revision: https://reviews.llvm.org/D76082
The SVE ACLE doesn't allow fields to have sizeless type. At the moment
clang accepts things like:
struct s { __SVInt8_t x; } y;
but trying to code-generate it leads to LLVM asserts like:
llvm/include/llvm/Support/TypeSize.h:126: uint64_t llvm::TypeSize::getFixedSize() const: Assertion `!IsScalable && "Request for a fixed size on a scalable object"' failed.
This patch adds an associated clang diagnostic.
Differential Revision: https://reviews.llvm.org/D75737
clang accepts a TU containing just:
__SVInt8_t x;
However, sizeless types are not allowed to have static or thread-local
storage duration and trying to code-generate the TU triggers an LLVM
fatal error:
Globals cannot contain scalable vectors
<vscale x 16 x i8>* @x
fatal error: error in backend: Broken module found, compilation aborted!
This patch adds an associated clang diagnostic.
Differential Revision: https://reviews.llvm.org/D75736
It would be difficult to guarantee atomicity for sizeless types,
so the SVE ACLE makes atomic sizeless types invalid. As it happens,
we already rejected them before the patch, but for the wrong reason:
error: _Atomic cannot be applied to type 'svint8_t' (aka '__SVInt8_t')
which is not trivially copyable
The SVE types should be treated as trivially copyable; a later
patch fixes that.
Differential Revision: https://reviews.llvm.org/D75734
A previous patch rejected alignof for sizeless types. This patch
extends that to cover the "aligned" attribute and _Alignas. Since
sizeless types are not meant to be used for long-term data, cannot
be used in aggregates, and cannot have static storage duration,
there shouldn't be any need to fiddle with their alignment.
Like with alignof, this is a conservative position that can be
relaxed in future if it turns out to be too restrictive.
Differential Revision: https://reviews.llvm.org/D75573
clang current accepts:
void foo1(__SVInt8_t *x, __SVInt8_t *y) { *x = *y; }
void foo2(__SVInt8_t *x, __SVInt8_t *y) {
memcpy(y, x, sizeof(__SVInt8_t));
}
The first function is valid ACLE code and generates correct LLVM IR.
However, the second function is invalid ACLE code and generates a
zero-length memcpy. The point of this patch is to reject the use
of sizeof in the second case instead.
There's no similar wrong-code bug for alignof. However, the SVE ACLE
conservatively treats alignof in the same way as sizeof, just as the
C++ standard does for incomplete types. The idea is that layout of
sizeless types is an implementation property and isn't defined at
the language level.
Implementation-wise, the patch adds a new CompleteTypeKind enum
that controls whether RequireCompleteType & friends accept sizeless
built-in types. For now the default is to maintain the status quo
and accept sizeless types. However, the end of the series will flip
the default and remove the Default enum value.
The patch also adds new ...CompleteSized... wrappers that callers can
use if they explicitly want to reject sizeless types. The callers then
use diagnostics that have an extra 0/1 parameter to indicats whether
the type is sizeless or not.
The idea is to have three cases:
1. calls that explicitly reject sizeless types, with a tweaked diagnostic
for the sizeless case
2. calls that explicitly allow sizeless types
3. normal/old-style calls that don't make an explicit choice either way
Once the default is flipped, the 3. calls will conservatively reject
sizeless types, using the same diagnostic as for other incomplete types.
Differential Revision: https://reviews.llvm.org/D75572
This patch adds C and C++ tests for various uses of SVE types.
The tests cover valid uses that are already (correctly) accepted and
invalid uses that are already (correctly) rejected. Later patches
will expand the tests as they fix other cases.[*]
Some of the tests for invalid uses aren't obviously related to
scalable vectors. Part of the reason for having them is to make
sure that the quality of the error message doesn't regress once/if
the types are treated as incomplete types.
[*] These later patches all fix invalid uses that are being incorrectly
accepted. I don't know of any cases in which valid uses are being
incorrectly rejected. In other words, this series is all about
diagnosing invalid code rather than enabling something new.
Differential Revision: https://reviews.llvm.org/D75571
Richard Sandiford