x86: Extend assembler to generate GNU property notes

Add -mx86-used-note=[yes|no] option to generate (or not) GNU property
notes with GNU_PROPERTY_X86_FEATURE_2_USED and GNU_PROPERTY_X86_ISA_1_USED
properties.  If the assembly input contains no instructions, set the
GNU_PROPERTY_X86_UINT32_VALID bit in GNU_PROPERTY_X86_FEATURE_2_USED
property.  Add a --enable-x86-used-note configure time option to set the
default behavior.  Set the default if the configure option is not used
to "no".

	* NEWS: Mention -mx86-used-note=[no|yes].
	* configure.ac: Add --enable-x86-used-note.  Define
	DEFAULT_X86_USED_NOTE.
	* config.in: Regenerated.
	* configure: Likewise.
	* config/tc-i386.c (x86_isa_1_used): New.
	(x86_feature_2_used): Likewise.
	(x86_used_note): Likewise.
	(_i386_insn): Add has_regmmx, has_regxmm, has_regymm and
	has_regzmm.
	(build_modrm_byte): Set i.has_regmmx, i.has_regzmm.
	i.has_regymm and i.has_regxmm.
	(x86_cleanup): New function.
	(output_insn): Update x86_isa_1_used and x86_feature_2_used.
	(OPTION_X86_USED_NOTE): New.
	(md_longopts): Add -mx86-used-note=.
	(md_parse_option): Handle OPTION_X86_USED_NOTE.
	(md_show_usage): Display -mx86-used-note=.
	* config/tc-i386.h (x86_cleanup): New prototype.
	(md_cleanup): New.
	* doc/c-i386.texi: Document -mx86-used-note=.

gas/ChangeLog

@@ -1,3 +1,27 @@
+2018-08-31  H.J. Lu  <hongjiu.lu@intel.com>
+
+	* NEWS: Mention -mx86-used-note=[no|yes].
+	* configure.ac: Add --enable-x86-used-note.  Define
+	DEFAULT_X86_USED_NOTE.
+	* config.in: Regenerated.
+	* configure: Likewise.
+	* config/tc-i386.c (x86_isa_1_used): New.
+	(x86_feature_2_used): Likewise.
+	(x86_used_note): Likewise.
+	(_i386_insn): Add has_regmmx, has_regxmm, has_regymm and
+	has_regzmm.
+	(build_modrm_byte): Set i.has_regmmx, i.has_regzmm.
+	i.has_regymm and i.has_regxmm.
+	(x86_cleanup): New function.
+	(output_insn): Update x86_isa_1_used and x86_feature_2_used.
+	(OPTION_X86_USED_NOTE): New.
+	(md_longopts): Add -mx86-used-note=.
+	(md_parse_option): Handle OPTION_X86_USED_NOTE.
+	(md_show_usage): Display -mx86-used-note=.
+	* config/tc-i386.h (x86_cleanup): New prototype.
+	(md_cleanup): New.
+	* doc/c-i386.texi: Document -mx86-used-note=.
+
 2018-08-30  Jose E. Marchesi  <jose.marchesi@oracle.com>
 
 	* testsuite/gas/sparc/leon.d: Disassemble v8 code also in sparc64

gas/NEWS

@@ -1,5 +1,10 @@
 -*- text -*-
 
+* Add -mx86-used-note=[yes|no] option to generate (or not) x86 GNU property
+  notes.  Add a --enable-x86-used-note configure time option to set the
+  default behavior.  Set the default if the configure option is not used
+  to "no".
+
 * Add support for the MIPS Loongson EXTensions R2 (EXT2) instructions.
 
 * Add support for the MIPS Loongson EXTensions (EXT) instructions.

gas/config.in

@@ -50,6 +50,10 @@
 /* Define to 1 if you want to generate x86 relax relocations by default. */
 #undef DEFAULT_GENERATE_X86_RELAX_RELOCATIONS
 
+/* Define to 1 if you want to generate GNU x86 used ISA and feature properties
+   by default. */
+#undef DEFAULT_X86_USED_NOTE
+
 /* Supported emulations. */
 #undef EMULATIONS
 

gas/config/tc-i386.c

@@ -188,6 +188,13 @@ static void s_bss (int);
 #endif
 #if defined (OBJ_ELF) || defined (OBJ_MAYBE_ELF)
 static void handle_large_common (int small ATTRIBUTE_UNUSED);
+
+/* GNU_PROPERTY_X86_ISA_1_USED.  */
+static unsigned int x86_isa_1_used;
+/* GNU_PROPERTY_X86_FEATURE_2_USED.  */
+static unsigned int x86_feature_2_used;
+/* Generate x86 used ISA and feature properties.  */
+static unsigned int x86_used_note = DEFAULT_X86_USED_NOTE;
 #endif
 
 static const char *default_arch = DEFAULT_ARCH;
@@ -332,6 +339,18 @@ struct _i386_insn
     unsigned int prefixes;
     unsigned char prefix[MAX_PREFIXES];
 
+    /* Has MMX register operands.  */
+    bfd_boolean has_regmmx;
+
+    /* Has XMM register operands.  */
+    bfd_boolean has_regxmm;
+
+    /* Has YMM register operands.  */
+    bfd_boolean has_regymm;
+
+    /* Has ZMM register operands.  */
+    bfd_boolean has_regzmm;
+
     /* RM and SIB are the modrm byte and the sib byte where the
        addressing modes of this insn are encoded.  */
     modrm_byte rm;
@@ -7054,6 +7073,21 @@ build_modrm_byte (void)
 	{
 	  i.rm.reg = i.op[dest].regs->reg_num;
 	  i.rm.regmem = i.op[source].regs->reg_num;
+	  if (i.op[dest].regs->reg_type.bitfield.regmmx
+	       || i.op[source].regs->reg_type.bitfield.regmmx)
+	    i.has_regmmx = TRUE;
+	  else if (i.op[dest].regs->reg_type.bitfield.regsimd
+		   || i.op[source].regs->reg_type.bitfield.regsimd)
+	    {
+	      if (i.types[dest].bitfield.zmmword
+		  || i.types[source].bitfield.zmmword)
+		i.has_regzmm = TRUE;
+	      else if (i.types[dest].bitfield.ymmword
+		       || i.types[source].bitfield.ymmword)
+		i.has_regymm = TRUE;
+	      else
+		i.has_regxmm = TRUE;
+	    }
 	  if ((i.op[dest].regs->reg_flags & RegRex) != 0)
 	    i.rex |= REX_R;
 	  if ((i.op[dest].regs->reg_flags & RegVRex) != 0)
@@ -7393,17 +7427,32 @@ build_modrm_byte (void)
 	  unsigned int vex_reg = ~0;
 
 	  for (op = 0; op < i.operands; op++)
-	    if (i.types[op].bitfield.reg
+	    {
-		|| i.types[op].bitfield.regmmx
+	      if (i.types[op].bitfield.reg
-		|| i.types[op].bitfield.regsimd
+		  || i.types[op].bitfield.regbnd
-		|| i.types[op].bitfield.regbnd
+		  || i.types[op].bitfield.regmask
-		|| i.types[op].bitfield.regmask
+		  || i.types[op].bitfield.sreg2
-		|| i.types[op].bitfield.sreg2
+		  || i.types[op].bitfield.sreg3
-		|| i.types[op].bitfield.sreg3
+		  || i.types[op].bitfield.control
-		|| i.types[op].bitfield.control
+		  || i.types[op].bitfield.debug
-		|| i.types[op].bitfield.debug
+		  || i.types[op].bitfield.test)
-		|| i.types[op].bitfield.test)
+		break;
-	      break;
+	      if (i.types[op].bitfield.regsimd)
+		{
+		  if (i.types[op].bitfield.zmmword)
+		    i.has_regzmm = TRUE;
+		  else if (i.types[op].bitfield.ymmword)
+		    i.has_regymm = TRUE;
+		  else
+		    i.has_regxmm = TRUE;
+		  break;
+		}
+	      if (i.types[op].bitfield.regmmx)
+		{
+		  i.has_regmmx = TRUE;
+		  break;
+		}
+	    }
 
 	  if (vex_3_sources)
 	    op = dest;
@@ -7783,12 +7832,219 @@ output_interseg_jump (void)
   md_number_to_chars (p + size, (valueT) i.op[0].imms->X_add_number, 2);
 }
 
+#if defined (OBJ_ELF) || defined (OBJ_MAYBE_ELF)
+void
+x86_cleanup (void)
+{
+  char *p;
+  asection *seg = now_seg;
+  subsegT subseg = now_subseg;
+  asection *sec;
+  unsigned int alignment, align_size_1;
+  unsigned int isa_1_descsz, feature_2_descsz, descsz;
+  unsigned int isa_1_descsz_raw, feature_2_descsz_raw;
+  unsigned int padding;
+
+  if (!IS_ELF || !x86_used_note)
+    return;
+
+  x86_isa_1_used |= GNU_PROPERTY_X86_UINT32_VALID;
+  x86_feature_2_used |= GNU_PROPERTY_X86_FEATURE_2_X86;
+
+  /* The .note.gnu.property section layout:
+
+     Field	Length		Contents
+     ----	----		----
+     n_namsz	4		4
+     n_descsz	4		The note descriptor size
+     n_type	4		NT_GNU_PROPERTY_TYPE_0
+     n_name	4		"GNU"
+     n_desc	n_descsz	The program property array
+     ....	....		....
+   */
+
+  /* Create the .note.gnu.property section.  */
+  sec = subseg_new (NOTE_GNU_PROPERTY_SECTION_NAME, 0);
+  bfd_set_section_flags (stdoutput, sec,
+			 (SEC_ALLOC
+			  | SEC_LOAD
+			  | SEC_DATA
+			  | SEC_HAS_CONTENTS
+			  | SEC_READONLY));
+
+  if (get_elf_backend_data (stdoutput)->s->elfclass == ELFCLASS64)
+    {
+      align_size_1 = 7;
+      alignment = 3;
+    }
+  else
+    {
+      align_size_1 = 3;
+      alignment = 2;
+    }
+
+  bfd_set_section_alignment (stdoutput, sec, alignment);
+  elf_section_type (sec) = SHT_NOTE;
+
+  /* GNU_PROPERTY_X86_ISA_1_USED: 4-byte type + 4-byte data size
+				  + 4-byte data  */
+  isa_1_descsz_raw = 4 + 4 + 4;
+  /* Align GNU_PROPERTY_X86_ISA_1_USED.  */
+  isa_1_descsz = (isa_1_descsz_raw + align_size_1) & ~align_size_1;
+
+  feature_2_descsz_raw = isa_1_descsz;
+  /* GNU_PROPERTY_X86_FEATURE_2_USED: 4-byte type + 4-byte data size
+				      + 4-byte data  */
+  feature_2_descsz_raw += 4 + 4 + 4;
+  /* Align GNU_PROPERTY_X86_FEATURE_2_USED.  */
+  feature_2_descsz = ((feature_2_descsz_raw + align_size_1)
+		      & ~align_size_1);
+
+  descsz = feature_2_descsz;
+  /* Section size: n_namsz + n_descsz + n_type + n_name + n_descsz.  */
+  p = frag_more (4 + 4 + 4 + 4 + descsz);
+
+  /* Write n_namsz.  */
+  md_number_to_chars (p, (valueT) 4, 4);
+
+  /* Write n_descsz.  */
+  md_number_to_chars (p + 4, (valueT) descsz, 4);
+
+  /* Write n_type.  */
+  md_number_to_chars (p + 4 * 2, (valueT) NT_GNU_PROPERTY_TYPE_0, 4);
+
+  /* Write n_name.  */
+  memcpy (p + 4 * 3, "GNU", 4);
+
+  /* Write 4-byte type.  */
+  md_number_to_chars (p + 4 * 4,
+		      (valueT) GNU_PROPERTY_X86_ISA_1_USED, 4);
+
+  /* Write 4-byte data size.  */
+  md_number_to_chars (p + 4 * 5, (valueT) 4, 4);
+
+  /* Write 4-byte data.  */
+  md_number_to_chars (p + 4 * 6, (valueT) x86_isa_1_used, 4);
+
+  /* Zero out paddings.  */
+  padding = isa_1_descsz - isa_1_descsz_raw;
+  if (padding)
+    memset (p + 4 * 7, 0, padding);
+
+  /* Write 4-byte type.  */
+  md_number_to_chars (p + isa_1_descsz + 4 * 4,
+		      (valueT) GNU_PROPERTY_X86_FEATURE_2_USED, 4);
+
+  /* Write 4-byte data size.  */
+  md_number_to_chars (p + isa_1_descsz + 4 * 5, (valueT) 4, 4);
+
+  /* Write 4-byte data.  */
+  md_number_to_chars (p + isa_1_descsz + 4 * 6,
+		      (valueT) x86_feature_2_used, 4);
+
+  /* Zero out paddings.  */
+  padding = feature_2_descsz - feature_2_descsz_raw;
+  if (padding)
+    memset (p + isa_1_descsz + 4 * 7, 0, padding);
+
+  /* We probably can't restore the current segment, for there likely
+     isn't one yet...  */
+  if (seg && subseg)
+    subseg_set (seg, subseg);
+}
+#endif
+
 static void
 output_insn (void)
 {
   fragS *insn_start_frag;
   offsetT insn_start_off;
 
+#if defined (OBJ_ELF) || defined (OBJ_MAYBE_ELF)
+  if (IS_ELF && x86_used_note)
+    {
+      if (i.tm.cpu_flags.bitfield.cpucmov)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_CMOV;
+      if (i.tm.cpu_flags.bitfield.cpusse)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_SSE;
+      if (i.tm.cpu_flags.bitfield.cpusse2)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_SSE2;
+      if (i.tm.cpu_flags.bitfield.cpusse3)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_SSE3;
+      if (i.tm.cpu_flags.bitfield.cpussse3)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_SSSE3;
+      if (i.tm.cpu_flags.bitfield.cpusse4_1)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_SSE4_1;
+      if (i.tm.cpu_flags.bitfield.cpusse4_2)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_SSE4_2;
+      if (i.tm.cpu_flags.bitfield.cpuavx)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_AVX;
+      if (i.tm.cpu_flags.bitfield.cpuavx2)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_AVX2;
+      if (i.tm.cpu_flags.bitfield.cpufma)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_FMA;
+      if (i.tm.cpu_flags.bitfield.cpuavx512f)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_AVX512F;
+      if (i.tm.cpu_flags.bitfield.cpuavx512cd)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_AVX512CD;
+      if (i.tm.cpu_flags.bitfield.cpuavx512er)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_AVX512ER;
+      if (i.tm.cpu_flags.bitfield.cpuavx512pf)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_AVX512PF;
+      if (i.tm.cpu_flags.bitfield.cpuavx512vl)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_AVX512VL;
+      if (i.tm.cpu_flags.bitfield.cpuavx512dq)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_AVX512DQ;
+      if (i.tm.cpu_flags.bitfield.cpuavx512bw)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_AVX512BW;
+      if (i.tm.cpu_flags.bitfield.cpuavx512_4fmaps)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_AVX512_4FMAPS;
+      if (i.tm.cpu_flags.bitfield.cpuavx512_4vnniw)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_AVX512_4VNNIW;
+      if (i.tm.cpu_flags.bitfield.cpuavx512_bitalg)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_AVX512_BITALG;
+      if (i.tm.cpu_flags.bitfield.cpuavx512ifma)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_AVX512_IFMA;
+      if (i.tm.cpu_flags.bitfield.cpuavx512vbmi)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_AVX512_VBMI;
+      if (i.tm.cpu_flags.bitfield.cpuavx512_vbmi2)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_AVX512_VBMI2;
+      if (i.tm.cpu_flags.bitfield.cpuavx512_vnni)
+	x86_isa_1_used |= GNU_PROPERTY_X86_ISA_1_AVX512_VNNI;
+
+      if (i.tm.cpu_flags.bitfield.cpu8087
+	  || i.tm.cpu_flags.bitfield.cpu287
+	  || i.tm.cpu_flags.bitfield.cpu387
+	  || i.tm.cpu_flags.bitfield.cpu687
+	  || i.tm.cpu_flags.bitfield.cpufisttp)
+	x86_feature_2_used |= GNU_PROPERTY_X86_FEATURE_2_X87;
+      /* Don't set GNU_PROPERTY_X86_FEATURE_2_MMX for prefetchtXXX nor
+	 Xfence instructions.  */
+      if (i.tm.base_opcode != 0xf18
+	  && i.tm.base_opcode != 0xf0d
+	  && i.tm.base_opcode != 0xfae
+	  && (i.has_regmmx
+	      || i.tm.cpu_flags.bitfield.cpummx
+	      || i.tm.cpu_flags.bitfield.cpua3dnow
+	      || i.tm.cpu_flags.bitfield.cpua3dnowa))
+	x86_feature_2_used |= GNU_PROPERTY_X86_FEATURE_2_MMX;
+      if (i.has_regxmm)
+	x86_feature_2_used |= GNU_PROPERTY_X86_FEATURE_2_XMM;
+      if (i.has_regymm)
+	x86_feature_2_used |= GNU_PROPERTY_X86_FEATURE_2_YMM;
+      if (i.has_regzmm)
+	x86_feature_2_used |= GNU_PROPERTY_X86_FEATURE_2_ZMM;
+      if (i.tm.cpu_flags.bitfield.cpufxsr)
+	x86_feature_2_used |= GNU_PROPERTY_X86_FEATURE_2_FXSR;
+      if (i.tm.cpu_flags.bitfield.cpuxsave)
+	x86_feature_2_used |= GNU_PROPERTY_X86_FEATURE_2_XSAVE;
+      if (i.tm.cpu_flags.bitfield.cpuxsaveopt)
+	x86_feature_2_used |= GNU_PROPERTY_X86_FEATURE_2_XSAVEOPT;
+      if (i.tm.cpu_flags.bitfield.cpuxsavec)
+	x86_feature_2_used |= GNU_PROPERTY_X86_FEATURE_2_XSAVEC;
+    }
+#endif
+
   /* Tie dwarf2 debug info to the address at the start of the insn.
      We can't do this after the insn has been output as the current
      frag may have been closed off.  eg. by frag_var.  */
@@ -10581,6 +10837,7 @@ const char *md_shortopts = "qnO::";
 #define OPTION_MAMD64 (OPTION_MD_BASE + 22)
 #define OPTION_MINTEL64 (OPTION_MD_BASE + 23)
 #define OPTION_MFENCE_AS_LOCK_ADD (OPTION_MD_BASE + 24)
+#define OPTION_X86_USED_NOTE (OPTION_MD_BASE + 25)
 
 struct option md_longopts[] =
 {
@@ -10592,6 +10849,7 @@ struct option md_longopts[] =
 #if defined (OBJ_ELF) || defined (OBJ_MAYBE_ELF)
   {"x32", no_argument, NULL, OPTION_X32},
   {"mshared", no_argument, NULL, OPTION_MSHARED},
+  {"mx86-used-note", required_argument, NULL, OPTION_X86_USED_NOTE},
 #endif
   {"divide", no_argument, NULL, OPTION_DIVIDE},
   {"march", required_argument, NULL, OPTION_MARCH},
@@ -10659,6 +10917,17 @@ md_parse_option (int c, const char *arg)
     case OPTION_MSHARED:
       shared = 1;
       break;
+
+    case OPTION_X86_USED_NOTE:
+      if (strcasecmp (arg, "yes") == 0)
+        x86_used_note = 1;
+      else if (strcasecmp (arg, "no") == 0)
+        x86_used_note = 0;
+      else
+        as_fatal (_("invalid -mx86-used-note= option: `%s'"), arg);
+      break;
+
+
 #endif
 #if (defined (OBJ_ELF) || defined (OBJ_MAYBE_ELF) \
      || defined (TE_PE) || defined (TE_PEP) || defined (OBJ_MACH_O))
@@ -11196,9 +11465,19 @@ md_show_usage (FILE *stream)
   -mnaked-reg             don't require `%%' prefix for registers\n"));
   fprintf (stream, _("\
   -madd-bnd-prefix        add BND prefix for all valid branches\n"));
+#if defined (OBJ_ELF) || defined (OBJ_MAYBE_ELF)
   fprintf (stream, _("\
   -mshared                disable branch optimization for shared code\n"));
-# if defined (TE_PE) || defined (TE_PEP)
+  fprintf (stream, _("\
+  -mx86-used-note=[no|yes] "));
+  if (DEFAULT_X86_USED_NOTE)
+    fprintf (stream, _("(default: yes)\n"));
+  else
+    fprintf (stream, _("(default: no)\n"));
+  fprintf (stream, _("\
+                          generate x86 used ISA and feature properties\n"));
+#endif
+#if defined (TE_PE) || defined (TE_PEP)
   fprintf (stream, _("\
   -mbig-obj               generate big object files\n"));
 #endif

gas/config/tc-i386.h

@@ -316,6 +316,11 @@ extern bfd_vma x86_64_section_letter (int, const char **);
 #define md_elf_section_letter(LETTER, PTR_MSG)	x86_64_section_letter (LETTER, PTR_MSG)
 #define md_elf_section_word(STR, LEN)		x86_64_section_word (STR, LEN)
 
+#if defined (OBJ_ELF) || defined (OBJ_MAYBE_ELF)
+extern void x86_cleanup (void);
+#define md_cleanup() x86_cleanup ()
+#endif
+
 #ifdef TE_PE
 
 #define O_secrel O_md1

gas/configure

@@ -808,6 +808,7 @@ enable_compressed_debug_sections
 enable_x86_relax_relocations
 enable_elf_stt_common
 enable_generate_build_notes
+enable_x86_used_note
 enable_werror
 enable_build_warnings
 with_cpu
@@ -1469,6 +1470,7 @@ Optional Features:
   --enable-generate-build-notes
                           generate GNU Build notes if none are provided by the
                           input
+  --enable-x86-used-note  generate GNU x86 used ISA and feature properties
   --enable-werror         treat compile warnings as errors
   --enable-build-warnings enable build-time compiler warnings
   --disable-nls           do not use Native Language Support
@@ -11335,7 +11337,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11338 "configure"
+#line 11340 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -11441,7 +11443,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11444 "configure"
+#line 11446 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -12111,6 +12113,19 @@ esac
 fi
 
 
+# Decide if the x86 ELF assembler should default to generating GNU x86
+# used ISA and feature properties.
+ac_default_generate_x86_used_note=unset
+# Provide a configuration option to override the default.
+# Check whether --enable-x86-used-note was given.
+if test "${enable_x86_used_note+set}" = set; then :
+  enableval=$enable_x86_used_note; case "${enableval}" in
+  yes)  ac_default_generate_x86_used_note=1 ;;
+  no)   ac_default_generate_x86_used_note=0 ;;
+esac
+fi
+
+
 using_cgen=no
 
 
@@ -13039,6 +13054,15 @@ cat >>confdefs.h <<_ACEOF
 _ACEOF
 
 
+if test ${ac_default_generate_x86_used_note} = unset; then
+  ac_default_generate_x86_used_note=0
+fi
+
+cat >>confdefs.h <<_ACEOF
+#define DEFAULT_X86_USED_NOTE $ac_default_generate_x86_used_note
+_ACEOF
+
+
 if test x$ac_default_compressed_debug_sections = xyes ; then
 
 $as_echo "#define DEFAULT_FLAG_COMPRESS_DEBUG 1" >>confdefs.h

gas/configure.ac

@@ -113,6 +113,19 @@ AC_ARG_ENABLE(generate_build_notes,
 esac])dnl
 
 
+# Decide if the x86 ELF assembler should default to generating GNU x86
+# used ISA and feature properties.
+ac_default_generate_x86_used_note=unset
+# Provide a configuration option to override the default.
+AC_ARG_ENABLE(x86-used-note,
+	      AS_HELP_STRING([--enable-x86-used-note],
+	      [generate GNU x86 used ISA and feature properties]),
+[case "${enableval}" in
+  yes)  ac_default_generate_x86_used_note=1 ;;
+  no)   ac_default_generate_x86_used_note=0 ;;
+esac])dnl
+
+
 using_cgen=no
 
 AM_BINUTILS_WARNINGS
@@ -613,6 +626,14 @@ AC_DEFINE_UNQUOTED(DEFAULT_GENERATE_BUILD_NOTES,
   [Define to 1 if you want to generate GNU Build attribute notes
    by default, if none are contained in the input.])
 
+if test ${ac_default_generate_x86_used_note} = unset; then
+  ac_default_generate_x86_used_note=0
+fi
+AC_DEFINE_UNQUOTED(DEFAULT_X86_USED_NOTE,
+  $ac_default_generate_x86_used_note,
+  [Define to 1 if you want to generate GNU x86 used ISA and feature
+   properties by default.])
+
 if test x$ac_default_compressed_debug_sections = xyes ; then
   AC_DEFINE(DEFAULT_FLAG_COMPRESS_DEBUG, 1, [Define if you want compressed debug sections by default.])
 fi

gas/doc/c-i386.texi

@@ -400,6 +400,15 @@ R_X86_64_REX_GOTPCRELX, in 64-bit mode.
 relocations.  The default can be controlled by a configure option
 @option{--enable-x86-relax-relocations}.
 
+@cindex @samp{-mx86-used-note=} option, i386
+@cindex @samp{-mx86-used-note=} option, x86-64
+@item -mx86-used-note=@var{no}
+@itemx -mx86-used-note=@var{yes}
+These options control whether the assembler should generate
+GNU_PROPERTY_X86_ISA_1_USED and GNU_PROPERTY_X86_FEATURE_2_USED
+GNU property notes.  The default can be controlled by the
+@option{--enable-x86-used-note} configure option.
+
 @cindex @samp{-mevexrcig=} option, i386
 @cindex @samp{-mevexrcig=} option, x86-64
 @item -mevexrcig=@var{rne}