Re: [off list] Re: [PATCH] x86: use 'rep bsf' syntax when assembler supports it

[Roland McGrath]

On Sun, Jul 1, 2012 at 1:08 AM, Uros Bizjak <ubiz...@gmail.com> wrote:
> Based on the observation above, the patch is OK for mainline, but
> please also handle "rep nop" case.

Here's the new version of the patch that does that.  Note that someone
needs to commit this for me, since I am not empowered to do it myself.


Thanks,
Roland


gcc/
2012-07-02  Roland McGrath  <mcgra...@google.com>

        * configure.ac (HAVE_AS_IX86_REP_LOCK_PREFIX): Also require that the
        assembler accept 'rep bsf ...', 'rep bsr ...', 'rep ret', and 'rep nop'.
        * configure: Regenerated.
        * config/i386/i386.md (simple_return_internal_long): Use %;
        (ctz<mode>2): Likewise.
        (*pause): Likewise.


diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index 60aa65a..f23c13c 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -11904,7 +11904,7 @@
   [(simple_return)
    (unspec [(const_int 0)] UNSPEC_REP)]
   "reload_completed"
-  "rep\;ret"
+  "rep%; ret"
   [(set_attr "length" "2")
    (set_attr "atom_unit" "jeu")
    (set_attr "length_immediate" "0")
@@ -12236,8 +12236,8 @@
   else if (optimize_function_for_size_p (cfun))
     ;
   else if (TARGET_GENERIC)
-    /* tzcnt expands to rep;bsf and we can use it even if !TARGET_BMI.  */
-    return "rep; bsf{<imodesuffix>}\t{%1, %0|%0, %1}";
+    /* tzcnt expands to 'rep bsf' and we can use it even if !TARGET_BMI.  */
+    return "rep%; bsf{<imodesuffix>}\t{%1, %0|%0, %1}";

   return "bsf{<imodesuffix>}\t{%1, %0|%0, %1}";
 }
@@ -18131,7 +18131,7 @@
   [(set (match_operand:BLK 0)
        (unspec:BLK [(match_dup 0)] UNSPEC_PAUSE))]
   ""
-  "rep; nop"
+  "rep%; nop"
   [(set_attr "length" "2")
    (set_attr "memory" "unknown")])

diff --git a/gcc/configure b/gcc/configure
index fd3be52..db81441 100755
--- a/gcc/configure
+++ b/gcc/configure
@@ -24791,7 +24791,11 @@ else
   if test x$gcc_cv_as != x; then
     $as_echo 'rep movsl
         lock addl %edi, (%eax,%esi)
-        lock orl $0, (%esp)' > conftest.s
+        lock orl $0, (%esp)
+        rep bsf %ecx, %eax
+        rep bsr %ecx, %eax
+        rep ret
+        rep nop' > conftest.s
     if { ac_try='$gcc_cv_as $gcc_cv_as_flags  -o conftest.o conftest.s >&5'
   { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
   (eval $ac_try) 2>&5
@@ -28693,4 +28697,3 @@ if test -n "$ac_unrecognized_opts" && test
"$enable_option_checking" != no; then
 $as_echo "$as_me: WARNING: unrecognized options: $ac_unrecognized_opts" >&2;}
 fi

-
diff --git a/gcc/configure.ac b/gcc/configure.ac
index 89644e2..3bc523d 100644
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -3642,7 +3642,11 @@ foo:     nop
         gcc_cv_as_ix86_rep_lock_prefix,,,
        [rep movsl
         lock addl %edi, (%eax,%esi)
-        lock orl $0, (%esp)],,
+        lock orl $0, (%esp)
+        rep bsf %ecx, %eax
+        rep bsr %ecx, %eax
+        rep ret
+        rep nop],,
         [AC_DEFINE(HAVE_AS_IX86_REP_LOCK_PREFIX, 1,
           [Define if the assembler supports 'rep <insn>, lock <insn>'.])])

@@ -5158,4 +5162,3 @@ done
 ],
 [subdirs='$subdirs'])
 AC_OUTPUT
-