[PATCH] x86: Use ud2 assembly mnemonic when available.

[Roland McGrath]

Non-ancient assemblers support the "ud2" mnemonic, so there is no need
to emit the literal opcode as data.

OK for trunk and 4.8?


Thanks,
Roland


gcc/
2014-02-13  Roland McGrath  <mcgra...@google.com>

        * configure.ac (HAVE_AS_IX86_UD2): New test for 'ud2' mnemonic.
        * configure: Regenerated.
        * config.in: Regenerated.
        * config/i386/i386.md (trap) [HAVE_AS_IX86_UD2]: Use the mnemonic
        instead of ASM_SHORT.

--- a/gcc/config.in
+++ b/gcc/config.in
@@ -375,6 +375,12 @@
 #endif


+/* Define if your assembler supports the 'ud2' mnemonic. */
+#ifndef USED_FOR_TARGET
+#undef HAVE_AS_IX86_UD2
+#endif
+
+
 /* Define if your assembler supports the lituse_jsrdirect relocation. */
 #ifndef USED_FOR_TARGET
 #undef HAVE_AS_JSRDIRECT_RELOCS
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -17843,7 +17843,13 @@
 (define_insn "trap"
   [(trap_if (const_int 1) (const_int 6))]
   ""
-  { return ASM_SHORT "0x0b0f"; }
+{
+#ifdef HAVE_AS_IX86_UD2
+  return "ud2";
+#else
+  return ASM_SHORT "0x0b0f";
+#endif
+}
   [(set_attr "length" "2")])

 (define_expand "prefetch"
--- a/gcc/configure
+++ b/gcc/configure
@@ -25109,6 +25109,37 @@ $as_echo "#define
HAVE_AS_IX86_REP_LOCK_PREFIX 1" >>confdefs.h

 fi

+    { $as_echo "$as_me:${as_lineno-$LINENO}: checking assembler for
ud2 mnemonic" >&5
+$as_echo_n "checking assembler for ud2 mnemonic... " >&6; }
+if test "${gcc_cv_as_ix86_ud2+set}" = set; then :
+  $as_echo_n "(cached) " >&6
+else
+  gcc_cv_as_ix86_ud2=no
+  if test x$gcc_cv_as != x; then
+    $as_echo 'ud2' > conftest.s
+    if { ac_try='$gcc_cv_as $gcc_cv_as_flags  -o conftest.o conftest.s >&5'
+  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; }
+    then
+       gcc_cv_as_ix86_ud2=yes
+    else
+      echo "configure: failed program was" >&5
+      cat conftest.s >&5
+    fi
+    rm -f conftest.o conftest.s
+  fi
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $gcc_cv_as_ix86_ud2" >&5
+$as_echo "$gcc_cv_as_ix86_ud2" >&6; }
+if test $gcc_cv_as_ix86_ud2 = yes; then
+
+$as_echo "#define HAVE_AS_IX86_UD2 1" >>confdefs.h
+
+fi
+
     { $as_echo "$as_me:${as_lineno-$LINENO}: checking assembler for
R_386_TLS_GD_PLT reloc" >&5
 $as_echo_n "checking assembler for R_386_TLS_GD_PLT reloc... " >&6; }
 if test "${gcc_cv_as_ix86_tlsgdplt+set}" = set; then :
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -3895,6 +3895,12 @@ foo:     nop
         [AC_DEFINE(HAVE_AS_IX86_REP_LOCK_PREFIX, 1,
           [Define if the assembler supports 'rep <insn>, lock <insn>'.])])

+    gcc_GAS_CHECK_FEATURE([ud2 mnemonic],
+       gcc_cv_as_ix86_ud2,,,
+       [ud2],,
+      [AC_DEFINE(HAVE_AS_IX86_UD2, 1,
+       [Define if your assembler supports the 'ud2' mnemonic.])])
+
     gcc_GAS_CHECK_FEATURE([R_386_TLS_GD_PLT reloc],
         gcc_cv_as_ix86_tlsgdplt,,,
        [call    tls_gd@tlsgdplt],