build: add Meson support

I was trying to package Vixl, but the SCons build system does not
provide an install target, so I would've had to add it. It seemed too
difficult, so I directly created a quite basic Meson build script.

It provides most features of the SCons script, except for tests and
benchmarks, while adding a rich install target, with library soname
versioning and a pkg-config file.

Meson is a simple yet powerful build system, and you're interested in
using it as your main build system I could add tests and benchmarks :)

meson.build

@@ -0,0 +1,142 @@
+# SPDX-FileCopyrightText: 2021 Andrea Pappacoda
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+project(
+  'vixl',
+  'cpp',
+  version: '5.1.0',
+  license: 'BSD-3-Clause',
+  meson_version: '>=0.49.0',
+  default_options: [
+    'cpp_std=c++14',
+    'buildtype=release',
+    'warning_level=3',
+    'werror=true',
+    'd_ndebug=if-release',
+    'b_lto=true'
+  ]
+)
+
+if get_option('debug')
+  add_project_arguments('-DVIXL_DEBUG', language: 'cpp')
+endif
+
+hosts_32bit = ['arc', 'arm', 'c2000', 'csky', 'mips', 'ppc', 'riscv32', 'rx', 'sparc', 'wasm32', 'x86']
+can_target_aarch64 = not (host_machine.cpu_family() in hosts_32bit)
+
+build_a32 = false
+build_t32 = false
+build_a64 = false
+
+targets = get_option('target')
+if 'auto' in targets or 'all' in targets
+  if can_target_aarch64 or 'all' in targets
+    add_project_arguments(
+      '-DVIXL_INCLUDE_TARGET_A32',
+      '-DVIXL_INCLUDE_TARGET_T32',
+      '-DVIXL_INCLUDE_TARGET_A64',
+      language: 'cpp'
+    )
+    build_a32 = true
+    build_t32 = true
+    build_a64 = true
+  else
+    add_project_arguments(
+      '-DVIXL_INCLUDE_TARGET_A32',
+      '-DVIXL_INCLUDE_TARGET_T32',
+      language: 'cpp'
+    )
+    build_a32 = true
+    build_t32 = true
+  endif
+else
+  if 'a32' in targets or 'aarch32' in targets
+    add_project_arguments(
+      '-DVIXL_INCLUDE_TARGET_A32',
+      language: 'cpp'
+    )
+    build_a32 = true
+  endif
+  if 't32' in targets or 'aarch32' in targets
+    add_project_arguments(
+      '-DVIXL_INCLUDE_TARGET_T32',
+      language: 'cpp'
+    )
+    build_t32 = true
+  endif
+  if 'a64' in targets or 'aarch64' in targets
+    add_project_arguments(
+      '-DVIXL_INCLUDE_TARGET_A64',
+      language: 'cpp'
+    )
+    build_a64 = true
+  endif
+endif
+
+target_sources = []
+if build_a32 or build_t32
+  subdir('src'/'aarch32')
+endif
+if build_a64
+  subdir('src'/'aarch64')
+endif
+
+if get_option('simulator') == 'auto'
+  if not (host_machine.cpu_family() == 'aarch64') and can_target_aarch64
+    add_project_arguments('-DVIXL_INCLUDE_SIMULATOR_AARCH64', language: 'cpp')
+  endif
+elif get_option('simulator') == 'aarch64'
+  if can_target_aarch64 and build_a64
+    add_project_arguments('-DVIXL_INCLUDE_SIMULATOR_AARCH64', language: 'cpp')
+  else
+    error('Building an AArch64 simulator implies that VIXL targets AArch64. Set `target` to include `aarch64` or `a64`.')
+  endif
+endif
+
+allocator = get_option('code_buffer_allocator')
+if (allocator == 'auto' and host_machine.system() == 'linux') or allocator == 'mmap'
+  add_project_arguments('-DVIXL_CODE_BUFFER_MMAP', language: 'cpp')
+else
+  add_project_arguments('-DVIXL_CODE_BUFFER_MALLOC', language: 'cpp')
+endif
+
+libvixl = library(
+  'vixl',
+  'src'/'code-buffer-vixl.cc',
+  'src'/'compiler-intrinsics-vixl.cc',
+  'src'/'cpu-features.cc',
+  'src'/'utils-vixl.cc',
+  sources: target_sources,
+  include_directories: 'src',
+  version: meson.project_version(),
+  install: true
+)
+
+vixl_dep = declare_dependency(link_with: libvixl, include_directories: 'src')
+
+if meson.version().version_compare('>=0.54.0')
+  meson.override_dependency('vixl', vixl_dep)
+endif
+
+install_headers(
+  'src'/'assembler-base-vixl.h',
+  'src'/'code-buffer-vixl.h',
+  'src'/'code-generation-scopes-vixl.h',
+  'src'/'compiler-intrinsics-vixl.h',
+  'src'/'cpu-features.h',
+  'src'/'globals-vixl.h',
+  'src'/'invalset-vixl.h',
+  'src'/'macro-assembler-interface.h',
+  'src'/'platform-vixl.h',
+  'src'/'pool-manager-impl.h',
+  'src'/'pool-manager.h',
+  'src'/'utils-vixl.h',
+  subdir: 'vixl'
+)
+
+import('pkgconfig').generate(
+  libvixl,
+  description: 'ARMv8 Runtime Code Generation Library',
+  url: 'https://github.com/Linaro/vixl'
+)

meson_options.txt

@@ -0,0 +1,27 @@
+# SPDX-FileCopyrightText: 2021 Andrea Pappacoda
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+option(
+  'target',
+  type: 'array',
+  choices: ['auto', 'all', 'aarch32', 'a32', 't32', 'aarch64', 'a64'],
+  value: ['auto'],
+  description: 'Target ISA/Architecture'
+)
+
+option(
+  'simulator',
+  type: 'combo',
+  choices: ['auto', 'aarch64', 'none'],
+  value: 'auto',
+  description: 'Simulators to include'
+)
+
+option(
+  'code_buffer_allocator',
+  type: 'combo',
+  choices: ['auto', 'malloc', 'mmap'],
+  value: 'auto',
+  description: 'Configure the allocation mechanism in the CodeBuffer'
+)

src/aarch32/meson.build

@@ -0,0 +1,31 @@
+# SPDX-FileCopyrightText: 2021 Andrea Pappacoda
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+# Need to wrap the filenames in files() otherwise this array would be treated
+# as a simple array of strings, and when used in the master meson.build they
+# would refer to nonexistent paths. Wrapping in files() ensures that the
+# filenames will be always relative to this directory, even if referenced in
+# a different one. As a general rule, when I need to refer to a file from a
+# different build directory I should wrap it in files().
+
+target_sources += [
+  files('assembler-aarch32.cc'),
+  files('constants-aarch32.cc'),
+  files('disasm-aarch32.cc'),
+  files('instructions-aarch32.cc'),
+  files('location-aarch32.cc'),
+  files('macro-assembler-aarch32.cc'),
+  files('operands-aarch32.cc'),
+]
+
+install_headers(
+  'assembler-aarch32.h',
+  'constants-aarch32.h',
+  'disasm-aarch32.h',
+  'instructions-aarch32.h',
+  'location-aarch32.h',
+  'macro-assembler-aarch32.h',
+  'operands-aarch32.h',
+  subdir: 'vixl'/'aarch32'
+)

src/aarch64/meson.build

@@ -0,0 +1,46 @@
+# SPDX-FileCopyrightText: 2021 Andrea Pappacoda
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+# Need to wrap the filenames in files() otherwise this array would be treated
+# as a simple array of strings, and when used in the master meson.build they
+# would refer to nonexistent paths. Wrapping in files() ensures that the
+# filenames will be always relative to this directory, even if referenced in
+# a different one. As a general rule, when I need to refer to a file from a
+# different build directory I should wrap it in files().
+
+target_sources += [
+  files('assembler-aarch64.cc'),
+  files('assembler-sve-aarch64.cc'),
+  files('cpu-aarch64.cc'),
+  files('cpu-features-auditor-aarch64.cc'),
+  files('decoder-aarch64.cc'),
+  files('disasm-aarch64.cc'),
+  files('instructions-aarch64.cc'),
+  files('logic-aarch64.cc'),
+  files('macro-assembler-aarch64.cc'),
+  files('macro-assembler-sve-aarch64.cc'),
+  files('operands-aarch64.cc'),
+  files('pointer-auth-aarch64.cc'),
+  files('registers-aarch64.cc'),
+  files('simulator-aarch64.cc'),
+]
+
+install_headers(
+  'abi-aarch64.h',
+  'assembler-aarch64.h',
+  'constants-aarch64.h',
+  'cpu-aarch64.h',
+  'cpu-features-auditor-aarch64.h',
+  'decoder-aarch64.h',
+  'decoder-constants-aarch64.h',
+  'decoder-visitor-map-aarch64.h',
+  'disasm-aarch64.h',
+  'instructions-aarch64.h',
+  'macro-assembler-aarch64.h',
+  'operands-aarch64.h',
+  'registers-aarch64.h',
+  'simulator-aarch64.h',
+  'simulator-constants-aarch64.h',
+  subdir: 'vixl'/'aarch64'
+)