Matthieu Longo <matthieu.longo@arm.com> writes:
> The previous implementation to emit AEABI build attributes did not
> support string values (asciz) in aeabi_subsection, and was not
> emitting values associated to tags in the assembly comments.
>
> This new approach provides a more user-friendly interface relying on
> typing, and improves the emitted assembly comments:
> * aeabi_attribute:
> ** Adds the interpreted value next to the tag in the assembly
> comment.
> ** Supports asciz values.
> * aeabi_subsection:
> ** Adds debug information for its parameters.
> ** Auto-detects the attribute types when declaring the subsection.
>
> Additionally, it is also interesting to note that the code was moved
> to a separate file to improve modularity and "releave" the 1000-lines
I think you dropped a 0. I wish it was only 1000 :-)
> long aarch64.cc file from a few lines. Finally, it introduces a new
> namespace "aarch64::" for AArch64 backend which reduce the length of
> function names by not prepending 'aarch64_' to each of them.
> [...]
> diff --git a/gcc/config/aarch64/aarch64-dwarf-metadata.h b/gcc/config/aarch64/aarch64-dwarf-metadata.h
> new file mode 100644
> index 00000000000..01f08ad073e
> --- /dev/null
> +++ b/gcc/config/aarch64/aarch64-dwarf-metadata.h
> @@ -0,0 +1,226 @@
> +/* DWARF metadata for AArch64 architecture.
> + Copyright (C) 2024 Free Software Foundation, Inc.
> + Contributed by ARM Ltd.
> +
> + This file is part of GCC.
> +
> + GCC is free software; you can redistribute it and/or modify it
> + under the terms of the GNU General Public License as published by
> + the Free Software Foundation; either version 3, or (at your option)
> + any later version.
> +
> + GCC is distributed in the hope that it will be useful, but
> + WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + General Public License for more details.
> +
> + You should have received a copy of the GNU General Public License
> + along with GCC; see the file COPYING3. If not see
> + <http://www.gnu.org/licenses/>. */
> +
> +#ifndef GCC_AARCH64_DWARF_METADATA_H
> +#define GCC_AARCH64_DWARF_METADATA_H
> +
> +#include "system.h"
We should drop this line. It's the .cc file's responsibility to
include system.h.
> +#include "vec.h"
> +
> +namespace aarch64 {
> +
> +enum attr_val_type : uint8_t
> +{
> + uleb128 = 0x0,
> + asciz = 0x1,
> +};
> +
> +enum BA_TagFeature_t : uint8_t
> +{
> + Tag_Feature_BTI = 1,
> + Tag_Feature_PAC = 2,
> + Tag_Feature_GCS = 3,
> +};
> +
> +template <typename T_tag, typename T_val>
> +struct aeabi_attribute
> +{
> + T_tag tag;
> + T_val value;
> +};
> +
> +template <typename T_tag, typename T_val>
> +aeabi_attribute<T_tag, T_val>
> +make_aeabi_attribute (T_tag tag, T_val val)
> +{
> + return aeabi_attribute<T_tag, T_val>{tag, val};
> +}
> +
> +namespace details {
> +
> +constexpr const char *
> +to_c_str (bool b)
> +{
> + return b ? "true" : "false";
> +}
> +
> +constexpr const char *
> +to_c_str (const char *s)
> +{
> + return s;
> +}
> +
> +constexpr const char *
> +to_c_str (attr_val_type t)
> +{
> + return (t == uleb128 ? "ULEB128"
> + : t == asciz ? "asciz"
> + : nullptr);
> +}
> +
> +constexpr const char *
> +to_c_str (BA_TagFeature_t feature)
> +{
> + return (feature == Tag_Feature_BTI ? "Tag_Feature_BTI"
> + : feature == Tag_Feature_PAC ? "Tag_Feature_PAC"
> + : feature == Tag_Feature_GCS ? "Tag_Feature_GCS"
> + : nullptr);
> +}
> +
> +template <
> + typename T,
> + typename = typename std::enable_if<std::is_unsigned<T>::value, T>::type
> +>
> +constexpr const char *
> +aeabi_attr_str_fmt (T phantom __attribute__((unused)))
FWIW, it would be ok to drop the parameter name and the attribute.
But it's ok as-is too, if you think it makes the intention clearer.
> +{
> + return "\t.aeabi_attribute %u, %u";
> +}
> +
> +constexpr const char *
> +aeabi_attr_str_fmt (const char *phantom __attribute__((unused)))
> +{
> + return "\t.aeabi_attribute %u, \"%s\"";
> +}
> [...]
> @@ -24834,17 +24808,21 @@ aarch64_start_file (void)
> asm_fprintf (asm_out_file, "\t.arch %s\n",
> aarch64_last_printed_arch_string.c_str ());
>
> - /* Check whether the current assembly supports gcs build attributes, if not
> - fallback to .note.gnu.property section. */
> + /* Check whether the current assembler supports AEABI build attributes, if
> + not fallback to .note.gnu.property section. */
> #if (HAVE_AS_AEABI_BUILD_ATTRIBUTES)
Just to note that, as with patch 2, I hope this could be:
if (HAVE_AS_AEABI_BUILD_ATTRIBUTES)
{
...
}
instead.
OK with those changes, thanks.
Richard
new file mode 100644
@@ -0,0 +1,226 @@
+/* DWARF metadata for AArch64 architecture.
+ Copyright (C) 2024 Free Software Foundation, Inc.
+ Contributed by ARM Ltd.
+
+ This file is part of GCC.
+
+ GCC is free software; you can redistribute it and/or modify it
+ under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3, or (at your option)
+ any later version.
+
+ GCC is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with GCC; see the file COPYING3. If not see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef GCC_AARCH64_DWARF_METADATA_H
+#define GCC_AARCH64_DWARF_METADATA_H
+
+#include "system.h"
+#include "vec.h"
+
+namespace aarch64 {
+
+enum attr_val_type : uint8_t
+{
+ uleb128 = 0x0,
+ asciz = 0x1,
+};
+
+enum BA_TagFeature_t : uint8_t
+{
+ Tag_Feature_BTI = 1,
+ Tag_Feature_PAC = 2,
+ Tag_Feature_GCS = 3,
+};
+
+template <typename T_tag, typename T_val>
+struct aeabi_attribute
+{
+ T_tag tag;
+ T_val value;
+};
+
+template <typename T_tag, typename T_val>
+aeabi_attribute<T_tag, T_val>
+make_aeabi_attribute (T_tag tag, T_val val)
+{
+ return aeabi_attribute<T_tag, T_val>{tag, val};
+}
+
+namespace details {
+
+constexpr const char *
+to_c_str (bool b)
+{
+ return b ? "true" : "false";
+}
+
+constexpr const char *
+to_c_str (const char *s)
+{
+ return s;
+}
+
+constexpr const char *
+to_c_str (attr_val_type t)
+{
+ return (t == uleb128 ? "ULEB128"
+ : t == asciz ? "asciz"
+ : nullptr);
+}
+
+constexpr const char *
+to_c_str (BA_TagFeature_t feature)
+{
+ return (feature == Tag_Feature_BTI ? "Tag_Feature_BTI"
+ : feature == Tag_Feature_PAC ? "Tag_Feature_PAC"
+ : feature == Tag_Feature_GCS ? "Tag_Feature_GCS"
+ : nullptr);
+}
+
+template <
+ typename T,
+ typename = typename std::enable_if<std::is_unsigned<T>::value, T>::type
+>
+constexpr const char *
+aeabi_attr_str_fmt (T phantom __attribute__((unused)))
+{
+ return "\t.aeabi_attribute %u, %u";
+}
+
+constexpr const char *
+aeabi_attr_str_fmt (const char *phantom __attribute__((unused)))
+{
+ return "\t.aeabi_attribute %u, \"%s\"";
+}
+
+template <
+ typename T,
+ typename = typename std::enable_if<std::is_unsigned<T>::value, T>::type
+>
+constexpr uint8_t
+aeabi_attr_val_for_fmt (T value)
+{
+ return static_cast<uint8_t>(value);
+}
+
+constexpr const char *
+aeabi_attr_val_for_fmt (const char *s)
+{
+ return s;
+}
+
+template <typename T_tag, typename T_val>
+void
+write (FILE *out_file, aeabi_attribute<T_tag, T_val> const &attr)
+{
+ asm_fprintf (out_file, aeabi_attr_str_fmt (T_val{}),
+ attr.tag, aeabi_attr_val_for_fmt (attr.value));
+ if (flag_debug_asm)
+ asm_fprintf (out_file, "\t%s %s: %s", ASM_COMMENT_START,
+ to_c_str (attr.tag), to_c_str (attr.value));
+ asm_fprintf (out_file, "\n");
+}
+
+template <
+ typename T,
+ typename = typename std::enable_if<std::is_unsigned<T>::value, T>::type
+>
+constexpr attr_val_type
+deduce_attr_av_type (T value __attribute__((unused)))
+{
+ return attr_val_type::uleb128;
+}
+
+constexpr attr_val_type
+deduce_attr_av_type (const char *value __attribute__((unused)))
+{
+ return attr_val_type::asciz;
+}
+
+} // namespace details
+
+/* AEABI subsections can be public or private. A subsection is public if it is
+ prefixed with "aeabi", private otherwise. The header of an AEABI subsection
+ is composed of a name (usually a vendor name), a status whether it is
+ optional or not, and the expected type of its associated attributes (ULEB128
+ or asciz). Note: The attributes in the same subsection have all the same
+ type. An attribute is composed of a tag identifier (ULEB128), and its value
+ (ULEB128 or asciz).
+
+ Syntax:
+ .aeabi_subsection NameOfTheSubsection: string (=asciz),
+ Optional: boolean (=ULEB128),
+ AttributeValueType: enum{ULEB128, asciz} (=ULEB128)
+ [
+ .aeabi_attribute TagIdentifier: ULEB128,
+ TagValue: Variant[ULEB128|asciz]
+ ]*
+
+ Example:
+ .aeabi_subsection .aeabi-feature-and-bits, 1, 0
+ // Optional: true, AttrValType: ULEB128
+ .aeabi_attribute 3, 1 // Tag_Feature_GCS: true
+
+ Note: The textual representations of the tag and its value are emitted as a
+ comment along their numerical representations to annotate the assembler
+ output when the developer flag '-dA' is provided. */
+template <
+ typename T_tag, /* The type of a tag. */
+ typename T_val, /* The type of a value. */
+ size_t N = 0 /* The number of expected attributes if we know it. */
+>
+class aeabi_subsection
+{
+ public:
+ aeabi_subsection (const char *name, bool optional)
+ : m_name (name),
+ m_optional (optional),
+ m_avtype (details::deduce_attr_av_type (T_val{}))
+ {}
+
+ /* Append an attribute to the subsection. */
+ void append (aeabi_attribute<T_tag, T_val> &&attr)
+ {
+ m_attributes.quick_push (std::move (attr));
+ }
+
+ /* Write the data to the assembly file. */
+ void write (FILE *out_file) const
+ {
+ asm_fprintf (out_file, "\t.aeabi_subsection %s, %u, %u",
+ m_name, static_cast<uint8_t> (m_optional),
+ static_cast<uint8_t> (m_avtype));
+ if (flag_debug_asm)
+ asm_fprintf (out_file, "\t%s Optional: %s, AttrValType: %s",
+ ASM_COMMENT_START,
+ details::to_c_str (m_optional),
+ details::to_c_str (m_avtype));
+ asm_fprintf (out_file, "\n");
+
+ for (auto const &attr : m_attributes)
+ details::write (out_file, attr);
+ }
+
+ /* Indicate if the subsection is empty. */
+ bool empty () const
+ {
+ return m_attributes.is_empty ();
+ }
+
+ private:
+ const char *m_name;
+ bool m_optional;
+ attr_val_type m_avtype;
+ auto_vec<aeabi_attribute<T_tag, T_val>, N> m_attributes;
+};
+
+} // namespace aarch64
+
+#endif /* GCC_AARCH64_DWARF_METADATA_H */
\ No newline at end of file
@@ -84,6 +84,7 @@
#include "rtlanal.h"
#include "tree-dfa.h"
#include "asan.h"
+#include "aarch64-dwarf-metadata.h"
#include "aarch64-feature-deps.h"
#include "config/arm/aarch-common.h"
#include "config/arm/aarch-common-protos.h"
@@ -24787,33 +24788,6 @@ aarch64_post_cfi_startproc (FILE *f, tree ignored ATTRIBUTE_UNUSED)
asm_fprintf (f, "\t.cfi_b_key_frame\n");
}
-/* This function is used to emit an AEABI attribute with tag and its associated
- value. We emit the numerical value of the tag and the textual tags as
- comment so that anyone reading the assembler output will know which tag is
- being set.
- example: .aeabi_attribute 3, 1 // Tag_Feature_GCS */
-
-void
-aarch64_emit_aeabi_attribute (const char *name, uint8_t num, uint8_t val)
-{
- asm_fprintf (asm_out_file, "\t.aeabi_attribute %u, %u", num, val);
- if (flag_debug_asm)
- asm_fprintf (asm_out_file, "\t%s %s", ASM_COMMENT_START, name);
- asm_fprintf (asm_out_file, "\n");
-}
-
-/* This function is used to emit an AEABI subsection with vendor name,
- optional status and value type.
- example: .aeabi_subsection .aeabi-feature-and-bits, 1, 0 */
-
-void
-aarch64_emit_aeabi_subsection (const char *name, uint8_t num, uint8_t val)
-{
- asm_fprintf (asm_out_file, "\t.aeabi_subsection %s, %u, %u\n",
- name, num, val);
-}
-
-
/* Implements TARGET_ASM_FILE_START. Output the assembly header. */
static void
@@ -24834,17 +24808,21 @@ aarch64_start_file (void)
asm_fprintf (asm_out_file, "\t.arch %s\n",
aarch64_last_printed_arch_string.c_str ());
- /* Check whether the current assembly supports gcs build attributes, if not
- fallback to .note.gnu.property section. */
+ /* Check whether the current assembler supports AEABI build attributes, if
+ not fallback to .note.gnu.property section. */
#if (HAVE_AS_AEABI_BUILD_ATTRIBUTES)
- if (aarch64_gcs_enabled ())
- {
- aarch64_emit_aeabi_subsection (".aeabi-feature-and-bits", 1, 0);
- aarch64_emit_aeabi_attribute ("Tag_Feature_GCS", 3, 1);
- }
+ using namespace aarch64;
+ aeabi_subsection<BA_TagFeature_t, bool, 3>
+ aeabi_subsec (".aeabi-feature-and-bits", true);
+
+ aeabi_subsec.append (
+ make_aeabi_attribute (Tag_Feature_GCS, aarch64_gcs_enabled ()));
+
+ if (!aeabi_subsec.empty ())
+ aeabi_subsec.write (asm_out_file);
#endif
- default_file_start ();
+ default_file_start ();
}
/* Emit load exclusive. */
@@ -6,7 +6,7 @@ int main()
return 0;
}
-/* { dg-final { scan-assembler "\.aeabi_subsection \.aeabi-feature-and-bits, 1, 0" } } */
-/* { dg-final { scan-assembler "\.aeabi_attribute 3, 1\t\/\/ Tag_Feature_GCS" } } */
+/* { dg-final { scan-assembler "\.aeabi_subsection \.aeabi-feature-and-bits, 1, 0\t\/\/ Optional: true, AttrValType: ULEB128" } } */
+/* { dg-final { scan-assembler "\.aeabi_attribute 3, 1\t\/\/ Tag_Feature_GCS: true" } } */
/* { dg-final { scan-assembler "\.section\t\.note\.gnu\.property" } } */
/* { dg-final { scan-assembler "\.word\t0x4\t\/\/ GNU_PROPERTY_AARCH64_FEATURE_1_AND \\(GCS\\)" } } */
\ No newline at end of file
@@ -6,7 +6,7 @@ int main()
return 0;
}
-/* { dg-final { scan-assembler "\.aeabi_subsection \.aeabi-feature-and-bits, 1, 0" } } */
-/* { dg-final { scan-assembler "\.aeabi_attribute 3, 1\t\/\/ Tag_Feature_GCS" } } */
+/* { dg-final { scan-assembler "\.aeabi_subsection \.aeabi-feature-and-bits, 1, 0\t\/\/ Optional: true, AttrValType: ULEB128" } } */
+/* { dg-final { scan-assembler "\.aeabi_attribute 3, 1\t\/\/ Tag_Feature_GCS: true" } } */
/* { dg-final { scan-assembler "\.section\t\.note\.gnu\.property" } } */
/* { dg-final { scan-assembler "\.word\t0x7\t\/\/ GNU_PROPERTY_AARCH64_FEATURE_1_AND \\(BTI, PAC, GCS\\)" } } */
\ No newline at end of file