PATCH: Pass -mtune=i686 to assembler when compiling for i686

["H.J. Lu" <hongjiu dot lu at intel dot com>]

Hi,

The newer x86 assembler takes -mtune=i686, which will generate
multi-byte nops, like

66 66 66 2e 0f 1f 84 00 00 00 00 00     data32 data32 nopw %cs:0x0(%eax,%eax,1)

This patch checks if assembler supports -mtune=i686 and uses it when
compiling for i686.

Thanks.


H.J.
--
2010-02-18  H.J. Lu  <hongjiu.lu@intel.com>

	* config.make.in (config-asflags-i686): New.

	* configure.in: Substitute libc_cv_as_i686.

	* sysdeps/i386/configure.in: Check if assembler supports
	-mtune=i686.

	* sysdeps/i386/i686/Makefile (CFLAGS-.oX): Add -Wa,-mtune=i686
	if assembler supports -mtune=i686.
	(ASFLAGS-.oX): Likewise.

diff --git a/config.make.in b/config.make.in
index d65706c..adfda9d 100644
--- a/config.make.in
+++ b/config.make.in
@@ -36,6 +36,7 @@ asflags-cpu = @libc_cv_cc_submachine@
 
 config-cflags-sse4 = @libc_cv_cc_sse4@
 config-cflags-avx = @libc_cv_cc_avx@
+config-asflags-i686 = @libc_cv_as_i686@
 
 defines = @DEFINES@
 sysincludes = @SYSINCLUDES@
diff --git a/configure b/configure
index 49ac30d..b6752d1 100755
--- a/configure
+++ b/configure
@@ -657,6 +657,7 @@ xcoff
 elf
 ldd_rewrite_script
 use_ldconfig
+libc_cv_as_i686
 libc_cv_cc_avx
 libc_cv_cc_sse4
 libc_cv_cpp_asm_debuginfo
@@ -8830,6 +8831,7 @@ fi
 
 
 
+
 if test $elf = yes; then
   cat >>confdefs.h <<\_ACEOF
 #define HAVE_ELF 1
diff --git a/configure.in b/configure.in
index 8e50602..56849df 100644
--- a/configure.in
+++ b/configure.in
@@ -2323,6 +2323,7 @@ dnl sysdeps/CPU/configure.in checks set this via arch-specific asm tests
 AC_SUBST(libc_cv_cpp_asm_debuginfo)
 AC_SUBST(libc_cv_cc_sse4)
 AC_SUBST(libc_cv_cc_avx)
+AC_SUBST(libc_cv_as_i686)
 
 AC_SUBST(use_ldconfig)
 AC_SUBST(ldd_rewrite_script)
diff --git a/sysdeps/i386/configure b/sysdeps/i386/configure
index f0c2758..7814b3b 100644
--- a/sysdeps/i386/configure
+++ b/sysdeps/i386/configure
@@ -637,3 +637,22 @@ if test $libc_cv_cc_sse4 = yes; then
 _ACEOF
 
 fi
+
+{ $as_echo "$as_me:$LINENO: checking for assembler -mtune=i686 support" >&5
+$as_echo_n "checking for assembler -mtune=i686 support... " >&6; }
+if test "${libc_cv_as_i686+set}" = set; then
+  $as_echo_n "(cached) " >&6
+else
+  if { ac_try='${CC-cc} -Wa,-mtune=i686 -xc /dev/null -S -o /dev/null'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  libc_cv_as_i686=yes
+else
+  libc_cv_as_i686=no
+fi
+fi
+{ $as_echo "$as_me:$LINENO: result: $libc_cv_as_i686" >&5
+$as_echo "$libc_cv_as_i686" >&6; }
diff --git a/sysdeps/i386/configure.in b/sysdeps/i386/configure.in
index 12dceaf..9fc7fa5 100644
--- a/sysdeps/i386/configure.in
+++ b/sysdeps/i386/configure.in
@@ -47,3 +47,11 @@ fi])
 if test $libc_cv_cc_sse4 = yes; then
   AC_DEFINE(HAVE_SSE4_SUPPORT)
 fi
+
+dnl Check if -Wa,-mtune=i686 works.
+AC_CACHE_CHECK(for assembler -mtune=i686 support, libc_cv_as_i686, [dnl
+if AC_TRY_COMMAND([${CC-cc} -Wa,-mtune=i686 -xc /dev/null -S -o /dev/null]); then
+  libc_cv_as_i686=yes
+else
+  libc_cv_as_i686=no
+fi])
diff --git a/sysdeps/i386/i686/Makefile b/sysdeps/i386/i686/Makefile
index dbcf1c3..e6b2924 100644
--- a/sysdeps/i386/i686/Makefile
+++ b/sysdeps/i386/i686/Makefile
@@ -9,3 +9,19 @@ stack-align-test-flags += -msse
 ifeq ($(subdir),string)
 sysdep_routines += cacheinfo
 endif
+
+ifeq (yes,$(config-asflags-i686))
+CFLAGS-.o += -Wa,-mtune=i686
+CFLAGS-.os += -Wa,-mtune=i686
+CFLAGS-.op += -Wa,-mtune=i686
+CFLAGS-.og += -Wa,-mtune=i686
+CFLAGS-.ob += -Wa,-mtune=i686
+CFLAGS-.oS += -Wa,-mtune=i686
+
+ASFLAGS-.o += -Wa,-mtune=i686
+ASFLAGS-.os += -Wa,-mtune=i686
+ASFLAGS-.op += -Wa,-mtune=i686
+ASFLAGS-.og += -Wa,-mtune=i686
+ASFLAGS-.ob += -Wa,-mtune=i686
+ASFLAGS-.oS += -Wa,-mtune=i686
+endif