[gcc r13-2946] aarch64: Tweak constness of option-related data

[Richard Sandiford <rsandifo@gcc.gnu.org>]

https://gcc.gnu.org/g:60dee638c8a7ae59c033868de7e7638c88b38ed2

commit r13-2946-g60dee638c8a7ae59c033868de7e7638c88b38ed2
Author: Richard Sandiford <richard.sandiford@arm.com>
Date:   Thu Sep 29 11:32:55 2022 +0100

    aarch64: Tweak constness of option-related data
    
    Some of the option structures have all-const member variables.
    That doesn't seem necessary: we can just use const on the objects
    that are supposed to be read-only.
    
    Also, with the new, more C++-heavy option handling, it seems
    better to use constexpr for the static data, to make sure that
    we're not adding unexpected overhead.
    
    gcc/
            * common/config/aarch64/aarch64-common.cc (aarch64_option_extension)
            (processor_name_to_arch, arch_to_arch_name): Remove const from
            member variables.
            (all_extensions, all_cores, all_architectures): Make a constexpr.
            * config/aarch64/aarch64.cc (processor): Remove const from
            member variables.
            (all_architectures): Make a constexpr.
            * config/aarch64/driver-aarch64.cc (aarch64_core_data)
            (aarch64_arch_driver_info): Remove const from member variables.
            (aarch64_cpu_data, aarch64_arches): Make a constexpr.
            (get_arch_from_id): Return a pointer to const.
            (host_detect_local_cpu): Update accordingly.

Diff:
---
 gcc/common/config/aarch64/aarch64-common.cc | 26 +++++++++++++-------------
 gcc/config/aarch64/aarch64.cc               | 14 +++++++-------
 gcc/config/aarch64/driver-aarch64.cc        | 15 +++++++--------
 3 files changed, 27 insertions(+), 28 deletions(-)

diff --git a/gcc/common/config/aarch64/aarch64-common.cc b/gcc/common/config/aarch64/aarch64-common.cc
index 8760e092064..918ac844dcf 100644
--- a/gcc/common/config/aarch64/aarch64-common.cc
+++ b/gcc/common/config/aarch64/aarch64-common.cc
@@ -127,14 +127,14 @@ aarch64_handle_option (struct gcc_options *opts,
 /* An ISA extension in the co-processor and main instruction set space.  */
 struct aarch64_option_extension
 {
-  const char *const name;
-  const uint64_t flag_canonical;
-  const uint64_t flags_on;
-  const uint64_t flags_off;
+  const char *name;
+  uint64_t flag_canonical;
+  uint64_t flags_on;
+  uint64_t flags_off;
 };
 
 /* ISA extensions in AArch64.  */
-static const struct aarch64_option_extension all_extensions[] =
+static constexpr aarch64_option_extension all_extensions[] =
 {
 #define AARCH64_OPT_EXTENSION(NAME, IDENT, C, D, E, F) \
   {NAME, AARCH64_FL_##IDENT, \
@@ -147,21 +147,21 @@ static const struct aarch64_option_extension all_extensions[] =
 
 struct processor_name_to_arch
 {
-  const char *const processor_name;
-  const enum aarch64_arch arch;
-  const uint64_t flags;
+  const char *processor_name;
+  aarch64_arch arch;
+  uint64_t flags;
 };
 
 struct arch_to_arch_name
 {
-  const enum aarch64_arch arch;
-  const char *const arch_name;
-  const uint64_t flags;
+  aarch64_arch arch;
+  const char *arch_name;
+  uint64_t flags;
 };
 
 /* Map processor names to the architecture revision they implement and
    the default set of architectural feature flags they support.  */
-static const struct processor_name_to_arch all_cores[] =
+static constexpr processor_name_to_arch all_cores[] =
 {
 #define AARCH64_CORE(NAME, CORE_IDENT, C, ARCH_IDENT, E, F, G, H, I) \
   {NAME, AARCH64_ARCH_##ARCH_IDENT, feature_deps::cpu_##CORE_IDENT},
@@ -171,7 +171,7 @@ static const struct processor_name_to_arch all_cores[] =
 };
 
 /* Map architecture revisions to their string representation.  */
-static const struct arch_to_arch_name all_architectures[] =
+static constexpr arch_to_arch_name all_architectures[] =
 {
 #define AARCH64_ARCH(NAME, B, ARCH_IDENT, D, E)	\
   {AARCH64_ARCH_##ARCH_IDENT, NAME, feature_deps::ARCH_IDENT ().enable},
diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index 398232433ce..70371afd1c5 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -2671,16 +2671,16 @@ aarch64_tuning_override_functions[] =
 /* A processor implementing AArch64.  */
 struct processor
 {
-  const char *const name;
-  enum aarch64_processor ident;
-  enum aarch64_processor sched_core;
-  enum aarch64_arch arch;
-  const uint64_t flags;
-  const struct tune_params *const tune;
+  const char *name;
+  aarch64_processor ident;
+  aarch64_processor sched_core;
+  aarch64_arch arch;
+  uint64_t flags;
+  const tune_params *tune;
 };
 
 /* Architectures implementing AArch64.  */
-static const struct processor all_architectures[] =
+static constexpr processor all_architectures[] =
 {
 #define AARCH64_ARCH(NAME, CORE, ARCH_IDENT, D, E) \
   {NAME, CORE, CORE, AARCH64_ARCH_##ARCH_IDENT, \
diff --git a/gcc/config/aarch64/driver-aarch64.cc b/gcc/config/aarch64/driver-aarch64.cc
index 1c86d62ef80..be41e2923db 100644
--- a/gcc/config/aarch64/driver-aarch64.cc
+++ b/gcc/config/aarch64/driver-aarch64.cc
@@ -50,7 +50,7 @@ struct aarch64_core_data
   unsigned char implementer_id; /* Exactly 8 bits */
   unsigned int part_no; /* 12 bits + 12 bits */
   unsigned variant;
-  const uint64_t flags;
+  uint64_t flags;
 };
 
 #define AARCH64_BIG_LITTLE(BIG, LITTLE) \
@@ -64,7 +64,7 @@ struct aarch64_core_data
 #define AARCH64_CORE(CORE_NAME, CORE_IDENT, SCHED, ARCH, FLAGS, COSTS, IMP, PART, VARIANT) \
   { CORE_NAME, #ARCH, IMP, PART, VARIANT, feature_deps::cpu_##CORE_IDENT },
 
-static struct aarch64_core_data aarch64_cpu_data[] =
+static constexpr aarch64_core_data aarch64_cpu_data[] =
 {
 #include "aarch64-cores.def"
   { NULL, NULL, INVALID_IMP, INVALID_CORE, ALL_VARIANTS, 0 }
@@ -75,14 +75,14 @@ struct aarch64_arch_driver_info
 {
   const char* id;
   const char* name;
-  const uint64_t flags;
+  uint64_t flags;
 };
 
 /* Skip the leading "V" in the architecture name.  */
 #define AARCH64_ARCH(NAME, CORE, ARCH_IDENT, ARCH_REV, FLAGS) \
   { #ARCH_IDENT + 1, NAME, feature_deps::ARCH_IDENT ().enable },
 
-static struct aarch64_arch_driver_info aarch64_arches[] =
+static constexpr aarch64_arch_driver_info aarch64_arches[] =
 {
 #include "aarch64-arches.def"
   {NULL, NULL, 0}
@@ -92,7 +92,7 @@ static struct aarch64_arch_driver_info aarch64_arches[] =
 /* Return an aarch64_arch_driver_info for the architecture described
    by ID, or NULL if ID describes something we don't know about.  */
 
-static struct aarch64_arch_driver_info*
+static const aarch64_arch_driver_info *
 get_arch_from_id (const char* id)
 {
   unsigned int i = 0;
@@ -396,8 +396,7 @@ host_detect_local_cpu (int argc, const char **argv)
 
       if (aarch64_cpu_data[i].name == NULL)
 	{
-	  aarch64_arch_driver_info* arch_info
-	    = get_arch_from_id (DEFAULT_ARCH);
+	  auto arch_info = get_arch_from_id (DEFAULT_ARCH);
 
 	  gcc_assert (arch_info);
 
@@ -407,7 +406,7 @@ host_detect_local_cpu (int argc, const char **argv)
       else if (arch)
 	{
 	  const char *arch_id = aarch64_cpu_data[i].arch;
-	  aarch64_arch_driver_info* arch_info = get_arch_from_id (arch_id);
+	  auto arch_info = get_arch_from_id (arch_id);
 
 	  /* We got some arch indentifier that's not in aarch64-arches.def?  */
 	  if (!arch_info)