[ARM] Rework Tag_CPU_arch build attribute value selection

=== 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.

3) Tag_CPU_arch lines are removed from expected output when the
detected architecture should be pre-ARMv4, since 0 is the Tag_CPU_arch
value for pre-ARMv4 architectures and default value for an absent entry
is 0.

2017-06-21  Thomas Preud'homme  <thomas.preudhomme@arm.com>

gas/
	* 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/
	* opcode/arm.h (FPU_ANY): New macro.

8 files changed, 231 insertions, 69 deletions

diff --git a/gas/ChangeLog b/gas/ChangeLog
index 16f0c4b..87eea61 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,22 @@
+2017-06-21  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.
+
 2017-06-21  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* testsuite/gas/i386/cet-intel.d: Updated.
diff --git a/gas/config/tc-arm.c b/gas/config/tc-arm.c
index a62c5f2..7767aa6 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;
@@ -26558,30 +26559,61 @@ 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.  This allows for build attribute selection results to be
+   stable when new architectures are added.  */
 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.  */
@@ -26603,18 +26635,162 @@ 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 so that results remains stable when new architectures
+     are added.
+   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.  */
@@ -26647,45 +26823,29 @@ 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])
@@ -26708,18 +26868,6 @@ 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);
 
@@ -26727,14 +26875,15 @@ 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 ac65977..d9730b5 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 0b574ef..39e3371 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 387e4a3..2c4dd62 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 3bd06e6..dfd17d2 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 13d5d18..988f896 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 4e24399..c946b37 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