Re: [PATCH 6/10, GAS/ARM] Rework Tag_CPU_arch build attribute value selection

["Richard Earnshaw (lists)" <Richard dot Earnshaw at arm dot com>]

On 21/06/17 11:12, Thomas Preudhomme wrote:
> Hi,
> 
> === Context ===
> 
> This patch is part of a patch series to add support for ARMv8-R
> architecture. Its purpose is to rework the Tag_CPU_arch build attribute
> value selection to (i) match architecture or CPU if specified by user
> without any need for hack and (ii) match an architecture with all the
> features used if in autodetection mode or return an error.
> 
> === Motivation ===
> 
> Currently, Tag_CPU_arch build attribute value selection assumes that an
> architecture is always a superset of architectures released earlier. As
> such, the logic is to browse architectures in chronological order of
> release and selecting the Tag_CPU_arch value of the last one to
> contribute a feature used[1]/requested[2] not contributed by earlier
> architectures.
> 
> [1] in case of autodetection mode
> [2] otherwise, ie. in case of -mcpu/-march or associated directives
> 
> This logic fails the two objectives mentionned in the Context section.
> First, due to the assumption it does an architecture can be selected
> while not having all the features used/requested which fails the second
> objective. Second, not doing an exact match when an architecture or CPU
> is selected by the user means the wrong value is chosen when a later
> architecture provides a subset of the feature bits of an earlier
> architecture. This is the case for the implementation of ARMv8-R (see
> later patch).
> 
> An added benefit of this patch is that it is possible to easily generate
> more consistent build attribute by setting the feature bits from the
> architecture matched in aeabi_set_public_attributes in autodetection
> mode. This is better done as a separate patch because lots of testcase'
> expected results must then be updated accordingly.
> 
> === Patch description ===
> 
> The patch changes the main logic for Tag_CPU_arch and Tag_CPU_arch_profile
> values selection to:
> - look for an exact match in case an architecture or CPU was specified
>   on the command line or in a directive
> - select the first released architecture that provides a superset of the
>   feature used in the autodetection case
> - select the most featureful architecture in case of -march=all
> The array cpu_arch_ver is updated to include all architectures in order
> to make the first point work.
> 
> Note that when looking for an exact match, the architecture with
> selected extension is tried first and then only the architecture. This
> is because some architectures are exactly equivalent to an earlier
> architecture with its extensions selected. ARMv6S-M (= ARMv6-M + OS
> extension) and ARMv6KZ (ARMv6K + security extension) are two such
> examples.
> 
> Other adjustments are also necessary in aeabi_set_public_attributes to
> make this change work.
> 
> 1) The logic to set Tag_ARM_ISA_use and Tag_THUMB_ISA_use must check the
> absence of feature bit used/requested to decide whether to give the
> default value for empty files (see EABI attribute defaults test). It was
> previously checking that arch == 0 which would only happen if no feature
> bit could be matched by any architecture, ie there is no feature bit to
> match.
> 
> 2) A fallback to a superset match must exist when no_cpu_selected ()
> returns true. This is because aeabi_set_public_attributes is called
> again after relaxation and at this point selected_cpu is set from the
> previous execution of that function. There is therefore no way to check
> whether the user specified an architecture or CPU.
> 
> ChangeLog entries are as follow:
> 
> *** gas/ChangeLog ***
> 
> 2017-06-13  Thomas Preud'homme  <thomas.preudhomme@arm.com>
> 
>     * config/tc-arm.c (fpu_any): Defined from FPU_ANY.
>     (cpu_arch_ver): Add all architectures and sort by release date.
>     (have_ext_for_needed_feat_p): New.
>     (get_aeabi_cpu_arch_from_fset): New.
>     (aeabi_set_public_attributes): Call above function to determine
>     Tag_CPU_arch and Tag_CPU_arch_profile values.  Adapt Tag_ARM_ISA_use
>     and Tag_THUMB_ISA_use selection logic to check absence of feature bit
>     accordingly.
>     * testsuite/gas/arm/attr-march-armv1.d: Fix expected Tag_CPU_arch build
>     attribute value.
>     * testsuite/gas/arm/attr-march-armv2.d: Likewise.
>     * testsuite/gas/arm/attr-march-armv2a.d: Likewise.
>     * testsuite/gas/arm/attr-march-armv2s.d: Likewise.
>     * testsuite/gas/arm/attr-march-armv3.d: Likewise.
>     * testsuite/gas/arm/attr-march-armv3m.d: Likewise.
>     * testsuite/gas/arm/pr12198-2.d: Likewise.
> 
> *** include/ChangeLog ***
> 
> 2017-01-26  Thomas Preud'homme  <thomas.preudhomme@arm.com>
> 
>     * opcode/arm.h (FPU_ANY): New macro.
> 
> === Testing ===
> 
> Testsuite shows no regression when run for arm-none-eabi targets.
> 
> Is this ok for master branch?
> 

I have two issues with this patch...

1)
> +/* Mapping from CPU features to EABI CPU arch values.  Table must be
sorted
> +   chronologically for architectures, with an exception for ARMv6-M and
> +   ARMv6S-M due to legacy reasons.  No new architecture should have a
> +   special case.  */

This comment warrants some justification.  We should explain that the
reason for maintaining chronological order is to avoid the build
attributes of object files changing as new variant architectures get added.

2)
>  File Attributes
>    Tag_CPU_name: "1"
> -  Tag_CPU_arch: v4
>    Tag_ARM_ISA_use: Yes

I think we should always emit a Tag_CPU_arch directive.  It's wrong to
assume that the consumer of an object file will be able to deduce the
base architecture from a simple CPU name - especially an odd-ball one
like '1' which isn't an official product name.

Tag_CPU_arch = v4 is probably the right thing to emit here - we don't
have tags for architectures older than that.

R.

> Best regards,
> 
> Thomas
> 
> 06_rework_Tag_CPU_arch_selection_logic.patch
> 
> 
> diff --git a/gas/config/tc-arm.c b/gas/config/tc-arm.c
> index 390698ef9272b96f5b4670ecdbd7c0a860658961..ae6c4ca6e4c9a1941ae148a5b1ba52339f2530d4 100644
> --- a/gas/config/tc-arm.c
> +++ b/gas/config/tc-arm.c
> @@ -240,6 +240,7 @@ static const arm_feature_set arm_ext_v8_3 =
>    ARM_FEATURE_CORE_HIGH (ARM_EXT2_V8_3A);
>  
>  static const arm_feature_set arm_arch_any = ARM_ANY;
> +static const arm_feature_set fpu_any = FPU_ANY;
>  static const arm_feature_set arm_arch_full ATTRIBUTE_UNUSED = ARM_FEATURE (-1, -1, -1);
>  static const arm_feature_set arm_arch_t2 = ARM_ARCH_THUMB2;
>  static const arm_feature_set arm_arch_none = ARM_ARCH_NONE;
> @@ -26528,30 +26529,60 @@ typedef struct
>    arm_feature_set flags;
>  } cpu_arch_ver_table;
>  
> -/* Mapping from CPU features to EABI CPU arch values.  As a general rule, table
> -   must be sorted least features first but some reordering is needed, eg. for
> -   Thumb-2 instructions to be detected as coming from ARMv6T2.  */
> +/* Mapping from CPU features to EABI CPU arch values.  Table must be sorted
> +   chronologically for architectures, with an exception for ARMv6-M and
> +   ARMv6S-M due to legacy reasons.  No new architecture should have a
> +   special case.  */
>  static const cpu_arch_ver_table cpu_arch_ver[] =
>  {
> +    {0, ARM_ARCH_V1},
> +    {0, ARM_ARCH_V2},
> +    {0, ARM_ARCH_V2S},
> +    {0, ARM_ARCH_V3},
> +    {0, ARM_ARCH_V3M},
> +    {1, ARM_ARCH_V4xM},
>      {1, ARM_ARCH_V4},
> +    {2, ARM_ARCH_V4TxM},
>      {2, ARM_ARCH_V4T},
> +    {3, ARM_ARCH_V5xM},
>      {3, ARM_ARCH_V5},
> +    {3, ARM_ARCH_V5TxM},
>      {3, ARM_ARCH_V5T},
> +    {4, ARM_ARCH_V5TExP},
>      {4, ARM_ARCH_V5TE},
>      {5, ARM_ARCH_V5TEJ},
>      {6, ARM_ARCH_V6},
> -    {9, ARM_ARCH_V6K},
>      {7, ARM_ARCH_V6Z},
> +    {7, ARM_ARCH_V6KZ},
> +    {9, ARM_ARCH_V6K},
> +    {8, ARM_ARCH_V6T2},
> +    {8, ARM_ARCH_V6KT2},
> +    {8, ARM_ARCH_V6ZT2},
> +    {8, ARM_ARCH_V6KZT2},
> +
> +    /* When assembling a file with only ARMv6-M or ARMv6S-M instruction, GNU as
> +       always selected build attributes to match those of ARMv6-M
> +       (resp. ARMv6S-M).  However, due to these architectures being a strict
> +       subset of ARMv7-M in terms of instructions available, ARMv7-M attributes
> +       would be selected when fully respecting chronology of architectures.
> +       It is thus necessary to make a special case of ARMv6-M and ARMv6S-M and
> +       move them before ARMv7 architectures.  */
>      {11, ARM_ARCH_V6M},
>      {12, ARM_ARCH_V6SM},
> -    {8, ARM_ARCH_V6T2},
> -    {10, ARM_ARCH_V7VE},
> +
> +    {10, ARM_ARCH_V7},
> +    {10, ARM_ARCH_V7A},
>      {10, ARM_ARCH_V7R},
>      {10, ARM_ARCH_V7M},
> +    {10, ARM_ARCH_V7VE},
> +    {13, ARM_ARCH_V7EM},
>      {14, ARM_ARCH_V8A},
> +    {14, ARM_ARCH_V8_1A},
> +    {14, ARM_ARCH_V8_2A},
> +    {14, ARM_ARCH_V8_3A},
>      {16, ARM_ARCH_V8M_BASE},
>      {17, ARM_ARCH_V8M_MAIN},
> -    {0, ARM_ARCH_NONE}
> +    {-1, ARM_ARCH_NONE}
>  };
>  
>  /* Set an attribute if it has not already been set by the user.  */
> @@ -26573,18 +26604,161 @@ aeabi_set_attribute_string (int tag, const char *value)
>      bfd_elf_add_proc_attr_string (stdoutput, tag, value);
>  }
>  
> +/* Return whether features in the *NEEDED feature set are available via
> +   extensions for the architecture whose feature set is *ARCH_FSET.  */
> +static bfd_boolean
> +have_ext_for_needed_feat_p (const arm_feature_set *arch_fset,
> +			    const arm_feature_set *needed)
> +{
> +  int i, nb_allowed_archs;
> +  arm_feature_set ext_fset;
> +  const struct arm_option_extension_value_table *opt;
> +
> +  ext_fset = arm_arch_none;
> +  for (opt = arm_extensions; opt->name != NULL; opt++)
> +    {
> +      /* Extension does not provide any feature we need.  */
> +      if (!ARM_CPU_HAS_FEATURE (*needed, opt->merge_value))
> +	continue;
> +
> +      nb_allowed_archs =
> +	sizeof (opt->allowed_archs) / sizeof (opt->allowed_archs[0]);
> +      for (i = 0; i < nb_allowed_archs; i++)
> +	{
> +	  /* Empty entry.  */
> +	  if (ARM_FEATURE_EQUAL (opt->allowed_archs[i], arm_arch_any))
> +	    break;
> +
> +	  /* Extension is available, add it.  */
> +	  if (ARM_FSET_CPU_SUBSET (opt->allowed_archs[i], *arch_fset))
> +	    ARM_MERGE_FEATURE_SETS (ext_fset, ext_fset, opt->merge_value);
> +	}
> +    }
> +
> +  /* Can we enable all features in *needed?  */
> +  return ARM_FSET_CPU_SUBSET (*needed, ext_fset);
> +}
> +
> +/* Select value for Tag_CPU_arch and Tag_CPU_arch_profile build attributes for
> +   a given architecture feature set *ARCH_EXT_FSET including extension feature
> +   set *EXT_FSET.  Selection logic used depend on EXACT_MATCH:
> +   - if true, check for an exact match of the architecture modulo extensions;
> +   - otherwise, select build attribute value of the first superset
> +     architecture released.
> +   For -march/-mcpu=all the build attribute value of the most featureful
> +   architecture is returned.  Tag_CPU_arch_profile result is returned in
> +   PROFILE.  */
> +static int
> +get_aeabi_cpu_arch_from_fset (const arm_feature_set *arch_ext_fset,
> +			      const arm_feature_set *ext_fset,
> +			      char *profile, int exact_match)
> +{
> +  arm_feature_set arch_fset;
> +  const cpu_arch_ver_table *p_ver, *p_ver_ret = NULL;
> +
> +  /* Select most featureful architecture with all its extensions if building
> +     for -march=all as the feature sets used to set build attributes.  */
> +  if (ARM_FEATURE_EQUAL (*arch_ext_fset, arm_arch_any))
> +    {
> +      /* Force revisiting of decision for each new architecture.  */
> +      gas_assert (MAX_TAG_CPU_ARCH <= TAG_CPU_ARCH_V8M_MAIN);
> +      *profile = 'A';
> +      return TAG_CPU_ARCH_V8;
> +    }
> +
> +  ARM_CLEAR_FEATURE (arch_fset, *arch_ext_fset, *ext_fset);
> +
> +  for (p_ver = cpu_arch_ver; p_ver->val != -1; p_ver++)
> +    {
> +      arm_feature_set known_arch_fset;
> +
> +      ARM_CLEAR_FEATURE (known_arch_fset, p_ver->flags, fpu_any);
> +      if (exact_match)
> +	{
> +	  /* Base architecture match user-specified architecture and
> +	     extensions, eg. ARMv6S-M matching -march=armv6-m+os.  */
> +	  if (ARM_FEATURE_EQUAL (*arch_ext_fset, known_arch_fset))
> +	    {
> +	      p_ver_ret = p_ver;
> +	      goto found;
> +	    }
> +	  /* Base architecture match user-specified architecture only
> +	     (eg. ARMv6-M in the same case as above).  Record it in case we
> +	     find a match with above condition.  */
> +	  else if (p_ver_ret == NULL
> +		   && ARM_FEATURE_EQUAL (arch_fset, known_arch_fset))
> +	    p_ver_ret = p_ver;
> +	}
> +      else
> +	{
> +
> +	  /* Architecture has all features wanted.  */
> +	  if (ARM_FSET_CPU_SUBSET (arch_fset, known_arch_fset))
> +	    {
> +	      arm_feature_set added_fset;
> +
> +	      /* Compute features added by this architecture over the one
> +		 recorded in p_ver_ret.  */
> +	      if (p_ver_ret != NULL)
> +		ARM_CLEAR_FEATURE (added_fset, known_arch_fset,
> +				   p_ver_ret->flags);
> +	      /* First architecture that match incl. with extensions, or the
> +		 only difference in features over the recorded match is
> +		 features that were optional and are now mandatory.  */
> +	      if (p_ver_ret == NULL
> +		  || ARM_FSET_CPU_SUBSET (added_fset, arch_fset))
> +		{
> +		  p_ver_ret = p_ver;
> +		  goto found;
> +		}
> +	    }
> +	  else if (p_ver_ret == NULL)
> +	    {
> +	      arm_feature_set needed_ext_fset;
> +
> +	      ARM_CLEAR_FEATURE (needed_ext_fset, arch_fset, known_arch_fset);
> +
> +	      /* Architecture has all features needed when using some
> +		 extensions.  Record it and continue searching in case there
> +		 exist an architecture providing all needed features without
> +		 the need for extensions (eg. ARMv6S-M Vs ARMv6-M with
> +		 OS extension).  */
> +	      if (have_ext_for_needed_feat_p (&known_arch_fset,
> +					      &needed_ext_fset))
> +		p_ver_ret = p_ver;
> +	    }
> +	}
> +    }
> +
> +  if (p_ver_ret == NULL)
> +    return -1;
> +
> +found:
> +  /* Tag_CPU_arch_profile.  */
> +  if (ARM_CPU_HAS_FEATURE (p_ver_ret->flags, arm_ext_v7a)
> +      || ARM_CPU_HAS_FEATURE (p_ver_ret->flags, arm_ext_v8)
> +      || (ARM_CPU_HAS_FEATURE (p_ver_ret->flags, arm_ext_atomics)
> +	  && !ARM_CPU_HAS_FEATURE (p_ver_ret->flags, arm_ext_v8m_m_only)))
> +    *profile = 'A';
> +  else if (ARM_CPU_HAS_FEATURE (p_ver_ret->flags, arm_ext_v7r))
> +    *profile = 'R';
> +  else if (ARM_CPU_HAS_FEATURE (p_ver_ret->flags, arm_ext_m))
> +    *profile = 'M';
> +  else
> +    *profile = '\0';
> +  return p_ver_ret->val;
> +}
> +
>  /* Set the public EABI object attributes.  */
>  static void
>  aeabi_set_public_attributes (void)
>  {
> -  int arch;
>    char profile;
> +  int arch = -1;
>    int virt_sec = 0;
>    int fp16_optional = 0;
> -  arm_feature_set flags;
> -  arm_feature_set tmp;
> -  arm_feature_set arm_arch_v8m_base = ARM_ARCH_V8M_BASE;
> -  const cpu_arch_ver_table *p;
> +  int skip_exact_match = 0;
> +  arm_feature_set flags, flags_arch, flags_ext;
>  
>    /* Autodetection mode, choose the architecture based the instructions
>       actually used.  */
> @@ -26617,45 +26791,29 @@ aeabi_set_public_attributes (void)
>    /* Allow the user to override the reported architecture.  */
>    if (object_arch)
>      {
> -      ARM_CLEAR_FEATURE (flags, flags, arm_arch_any);
> -      ARM_MERGE_FEATURE_SETS (flags, flags, *object_arch);
> +      ARM_CLEAR_FEATURE (flags_arch, *object_arch, fpu_any);
> +      flags_ext = arm_arch_none;
>      }
> -
> -  tmp = flags;
> -  arch = 0;
> -  for (p = cpu_arch_ver; p->val; p++)
> +  else
>      {
> -      if (ARM_CPU_HAS_FEATURE (tmp, p->flags))
> -	{
> -	  arch = p->val;
> -	  ARM_CLEAR_FEATURE (tmp, tmp, p->flags);
> -	}
> -    }
> -
> -  /* The table lookup above finds the last architecture to contribute
> -     a new feature.  Unfortunately, Tag13 is a subset of the union of
> -     v6T2 and v7-M, so it is never seen as contributing a new feature.
> -     We can not search for the last entry which is entirely used,
> -     because if no CPU is specified we build up only those flags
> -     actually used.  Perhaps we should separate out the specified
> -     and implicit cases.  Avoid taking this path for -march=all by
> -     checking for contradictory v7-A / v7-M features.  */
> -  if (arch == TAG_CPU_ARCH_V7
> -      && !ARM_CPU_HAS_FEATURE (flags, arm_ext_v7a)
> -      && ARM_CPU_HAS_FEATURE (flags, arm_ext_v7m)
> -      && ARM_CPU_HAS_FEATURE (flags, arm_ext_v6_dsp))
> -    arch = TAG_CPU_ARCH_V7E_M;
> -
> -  ARM_CLEAR_FEATURE (tmp, flags, arm_arch_v8m_base);
> -  if (arch == TAG_CPU_ARCH_V8M_BASE && ARM_CPU_HAS_FEATURE (tmp, arm_arch_any))
> -    arch = TAG_CPU_ARCH_V8M_MAIN;
> -
> -  /* In cpu_arch_ver ARMv8-A is before ARMv8-M for atomics to be detected as
> -     coming from ARMv8-A.  However, since ARMv8-A has more instructions than
> -     ARMv8-M, -march=all must be detected as ARMv8-A.  */
> -  if (arch == TAG_CPU_ARCH_V8M_MAIN
> -      && ARM_FEATURE_CORE_EQUAL (selected_cpu, arm_arch_any))
> -    arch = TAG_CPU_ARCH_V8;
> +      ARM_CLEAR_FEATURE (flags_arch, flags, fpu_any);
> +      flags_ext = dyn_mcpu_ext_opt ? *dyn_mcpu_ext_opt : arm_arch_none;
> +      skip_exact_match = ARM_FEATURE_EQUAL (selected_cpu, arm_arch_any);
> +    }
> +
> +  /* When this function is run again after relaxation has happened there is no
> +     way to determine whether an architecture or CPU was specified by the user:
> +     - selected_cpu is set above for relaxation to work;
> +     - march_cpu_opt is not set if only -mcpu or .cpu is used;
> +     - mcpu_cpu_opt is set to arm_arch_any for autodetection.
> +     Therefore, if not in -march=all case we first try an exact match and fall
> +     back to autodetection.  */
> +  if (!skip_exact_match)
> +    arch = get_aeabi_cpu_arch_from_fset (&flags_arch, &flags_ext, &profile, 1);
> +  if (arch == -1)
> +    arch = get_aeabi_cpu_arch_from_fset (&flags_arch, &flags_ext, &profile, 0);
> +  if (arch == -1)
> +    as_bad (_("no architecture contains all the instructions used\n"));
>  
>    /* Tag_CPU_name.  */
>    if (selected_cpu_name[0])
> @@ -26678,18 +26836,6 @@ aeabi_set_public_attributes (void)
>    aeabi_set_attribute_int (Tag_CPU_arch, arch);
>  
>    /* Tag_CPU_arch_profile.  */
> -  if (ARM_CPU_HAS_FEATURE (flags, arm_ext_v7a)
> -      || ARM_CPU_HAS_FEATURE (flags, arm_ext_v8)
> -      || (ARM_CPU_HAS_FEATURE (flags, arm_ext_atomics)
> -	  && !ARM_CPU_HAS_FEATURE (flags, arm_ext_v8m_m_only)))
> -    profile = 'A';
> -  else if (ARM_CPU_HAS_FEATURE (flags, arm_ext_v7r))
> -    profile = 'R';
> -  else if (ARM_CPU_HAS_FEATURE (flags, arm_ext_m))
> -    profile = 'M';
> -  else
> -    profile = '\0';
> -
>    if (profile != '\0')
>      aeabi_set_attribute_int (Tag_CPU_arch_profile, profile);
>  
> @@ -26697,14 +26843,15 @@ aeabi_set_public_attributes (void)
>    if (dyn_mcpu_ext_opt && ARM_CPU_HAS_FEATURE (*dyn_mcpu_ext_opt, arm_ext_dsp))
>      aeabi_set_attribute_int (Tag_DSP_extension, 1);
>  
> +  ARM_CLEAR_FEATURE (flags_arch, flags, fpu_any);
>    /* Tag_ARM_ISA_use.  */
>    if (ARM_CPU_HAS_FEATURE (flags, arm_ext_v1)
> -      || arch == 0)
> +      || ARM_FEATURE_ZERO (flags_arch))
>      aeabi_set_attribute_int (Tag_ARM_ISA_use, 1);
>  
>    /* Tag_THUMB_ISA_use.  */
>    if (ARM_CPU_HAS_FEATURE (flags, arm_ext_v4t)
> -      || arch == 0)
> +      || ARM_FEATURE_ZERO (flags_arch))
>      {
>        int thumb_isa_use;
>  
> diff --git a/gas/testsuite/gas/arm/attr-march-armv1.d b/gas/testsuite/gas/arm/attr-march-armv1.d
> index ac6597743ea4c9e408f656d0b264052a17ae0a66..d9730b5d58bd50c69293926c67f0340dd95e4a02 100644
> --- a/gas/testsuite/gas/arm/attr-march-armv1.d
> +++ b/gas/testsuite/gas/arm/attr-march-armv1.d
> @@ -8,5 +8,4 @@
>  Attribute Section: aeabi
>  File Attributes
>    Tag_CPU_name: "1"
> -  Tag_CPU_arch: v4
>    Tag_ARM_ISA_use: Yes
> diff --git a/gas/testsuite/gas/arm/attr-march-armv2.d b/gas/testsuite/gas/arm/attr-march-armv2.d
> index 0b574efbbbc59d111232000ddb2e8003419cd6d5..39e337192957a82718da5bbd137ee3fe546a3fe0 100644
> --- a/gas/testsuite/gas/arm/attr-march-armv2.d
> +++ b/gas/testsuite/gas/arm/attr-march-armv2.d
> @@ -8,5 +8,4 @@
>  Attribute Section: aeabi
>  File Attributes
>    Tag_CPU_name: "2"
> -  Tag_CPU_arch: v4
>    Tag_ARM_ISA_use: Yes
> diff --git a/gas/testsuite/gas/arm/attr-march-armv2a.d b/gas/testsuite/gas/arm/attr-march-armv2a.d
> index 387e4a318041428cb07c914a9980ee4fe5604d80..2c4dd620d3d690474ebb862b1ac340f24d3500de 100644
> --- a/gas/testsuite/gas/arm/attr-march-armv2a.d
> +++ b/gas/testsuite/gas/arm/attr-march-armv2a.d
> @@ -8,5 +8,4 @@
>  Attribute Section: aeabi
>  File Attributes
>    Tag_CPU_name: "2A"
> -  Tag_CPU_arch: v4
>    Tag_ARM_ISA_use: Yes
> diff --git a/gas/testsuite/gas/arm/attr-march-armv2s.d b/gas/testsuite/gas/arm/attr-march-armv2s.d
> index 3bd06e62f070e1433671bbf2e7a3b6ab0cbf9ce3..dfd17d2b37716ac2d5d167020e0fb957b81b2f85 100644
> --- a/gas/testsuite/gas/arm/attr-march-armv2s.d
> +++ b/gas/testsuite/gas/arm/attr-march-armv2s.d
> @@ -8,5 +8,4 @@
>  Attribute Section: aeabi
>  File Attributes
>    Tag_CPU_name: "2S"
> -  Tag_CPU_arch: v4
>    Tag_ARM_ISA_use: Yes
> diff --git a/gas/testsuite/gas/arm/attr-march-armv3.d b/gas/testsuite/gas/arm/attr-march-armv3.d
> index 13d5d183946d099a10d3f026d2f1d4aae878cea9..988f896529370f353e2f64d1f56f703c12408eed 100644
> --- a/gas/testsuite/gas/arm/attr-march-armv3.d
> +++ b/gas/testsuite/gas/arm/attr-march-armv3.d
> @@ -8,5 +8,4 @@
>  Attribute Section: aeabi
>  File Attributes
>    Tag_CPU_name: "3"
> -  Tag_CPU_arch: v4
>    Tag_ARM_ISA_use: Yes
> diff --git a/gas/testsuite/gas/arm/attr-march-armv3m.d b/gas/testsuite/gas/arm/attr-march-armv3m.d
> index 4e2439972d84ea0e385f1b6d1fc24326505eacf0..c946b37177a91bdbae616094cb5671bdc26bd8cf 100644
> --- a/gas/testsuite/gas/arm/attr-march-armv3m.d
> +++ b/gas/testsuite/gas/arm/attr-march-armv3m.d
> @@ -8,5 +8,4 @@
>  Attribute Section: aeabi
>  File Attributes
>    Tag_CPU_name: "3M"
> -  Tag_CPU_arch: v4
>    Tag_ARM_ISA_use: Yes
> diff --git a/include/opcode/arm.h b/include/opcode/arm.h
> index bb68a78154a41d577ffa293b19b951dcd7085247..5691a85545cf924383f9c73d9ce9a97a3a835cdf 100644
> --- a/include/opcode/arm.h
> +++ b/include/opcode/arm.h
> @@ -285,6 +285,7 @@
>  #define ARM_ARCH_NONE	ARM_FEATURE_LOW (0, 0)
>  #define FPU_NONE	ARM_FEATURE_LOW (0, 0)
>  #define ARM_ANY		ARM_FEATURE (-1, -1, 0)	/* Any basic core.  */
> +#define FPU_ANY		ARM_FEATURE_COPROC (-1) /* Any FPU.  */
>  #define ARM_FEATURE_ALL	ARM_FEATURE (-1, -1, -1)/* All CPU and FPU features.  */
>  #define FPU_ANY_HARD	ARM_FEATURE_COPROC (FPU_FPA | FPU_VFP_HARD | FPU_MAVERICK)
>  /* Extensions containing some Thumb-2 instructions.  If any is present, Thumb
>