[PATCH] D83550: [PATCH 1/4][Sema][AArch64] Add parsing support for arm_sve_vector_bits attribute

[Cullen Rhodes via Phabricator via cfe-commits]

c-rhodes created this revision.
c-rhodes added reviewers: sdesmalen, rsandifo-arm, efriedma, ctetreau, cameron.mcinally.
Herald added subscribers: danielkiss, kristof.beyls, tschuett.
Herald added a reviewer: rengolin.
Herald added a reviewer: aaron.ballman.
Herald added a project: clang.

This patch implements parsing support for the 'arm_sve_vector_bits' type
attribute, defined by the Arm C Language Extensions (ACLE, version 00bet5,
section 3.7.3) for SVE [1].

The purpose of this attribute is to define fixed-length (VLST) versions
of existing sizeless types (VLAT). For example:

  #if __ARM_FEATURE_SVE_BITS==512
  typedef svint32_t fixed_svint32_t __attribute__((arm_sve_vector_bits(512)));
  #endif

Creates a type 'fixed_svint32_t' that is a fixed-length version of
'svint32_t' that is normal-sized (rather than sizeless) and contains
exactly 512 bits. Unlike 'svint32_t', this type can be used in places
such as structs and arrays where sizeless types can't.

Implemented in this patch is the following:

- Defined and tested attribute taking single argument.
- Checks the argument is an integer constant expression.
- Attribute can only be attached to a single SVE vector or predicate type, excluding tuple types such as svint32x4_t.
- Validates N == __ARM_FEATURE_SVE_BITS, where N is the number of bits passed to the attribute.
- Basic validation of the __ARM_FEATURE_SVE_BITS macro.

The __ARM_FEATURE_SVE_BITS macro will be enabled by the
-msve-vector-bits=<bits> flag in the final patch of the series.

[1] https://developer.arm.com/documentation/100987/latest


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D83550

Files:
  clang/include/clang/AST/Type.h
  clang/include/clang/Basic/Attr.td
  clang/include/clang/Basic/DiagnosticSemaKinds.td
  clang/lib/AST/Type.cpp
  clang/lib/AST/TypePrinter.cpp
  clang/lib/Sema/SemaType.cpp
  clang/test/Sema/arm-feature-sve-bits-macro.c
  clang/test/Sema/attr-arm-sve-vector-bits.c

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