[PATCH][AArch64][4.8] Add --enable-fix-cortex-a53-835769 configure option

[Kyrill Tkachov <kyrylo dot tkachov at arm dot com>]

Hi all,

This is the 4.8 backport of the configure option 
--enable-fix-cortex-a53-835769 to enable the workaround
for the Cortex-A53 erratum 835769 by default. The patch is very similar 
to the trunk version, just some
differences in the placement of the relevant sections.

Bootstrapped and tested on aarch64-none-linux-gnu.

Ok for the 4.8 branch together with the -mfix-cortex-a53-835769 option 
backport?

Thanks,
Kyrill

2014-10-17  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

    * config.gcc (aarch64*-*-*): Define TARGET_FIX_ERR_A53_835769_DEFAULT
    if asked.
    * configure.ac: Add --enable-fix-cortex-a53-835769 option.
    * configure: Regenerate.
    * config/aarch64/aarch64.c (aarch64_override_options): Handle
    TARGET_FIX_ERR_A53_835769_DEFAULT.
    * config/aarch64/aarch64.opt (mfix-cortex-a53-835769): Set Init value
    to 2.
    * doc/install.texi: Document --enable-fix-cortex-a53-835769 option.

commit 14eac44c8d83489908b9abf489f0ea5d7928d32b
Author: Kyrill Tkachov <kyrylo.tkachov@arm.com>
Date:   Mon Oct 13 11:22:55 2014 +0000

    [AArch64] Add --enable-fix-cortex-a53-835769 configure option

diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index c18697e..4323f5a 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -4848,6 +4848,15 @@ aarch64_override_options (void)
   aarch64_tune = selected_tune->core;
   aarch64_tune_params = selected_tune->tune;
 
+  if (aarch64_fix_a53_err835769 == 2)
+    {
+#ifdef TARGET_FIX_ERR_A53_835769_DEFAULT
+      aarch64_fix_a53_err835769 = 1;
+#else
+      aarch64_fix_a53_err835769 = 0;
+#endif
+    }
+
   aarch64_override_options_after_change ();
 }
 
diff --git a/gcc/config/aarch64/aarch64.opt b/gcc/config/aarch64/aarch64.opt
index f414ad4..f7c70bf 100644
--- a/gcc/config/aarch64/aarch64.opt
+++ b/gcc/config/aarch64/aarch64.opt
@@ -68,7 +68,7 @@ Target Report RejectNegative Mask(GENERAL_REGS_ONLY)
 Generate code which uses only the general registers
 
 mfix-cortex-a53-835769
-Target Report Var(aarch64_fix_a53_err835769) Init(0)
+Target Report Var(aarch64_fix_a53_err835769) Init(2)
 Workaround for ARM Cortex-A53 Erratum number 835769
 
 mlittle-endian
diff --git a/gcc/configure b/gcc/configure
index 3793681..94cce4e 100755
--- a/gcc/configure
+++ b/gcc/configure
@@ -910,6 +910,7 @@ with_plugin_ld
 enable_gnu_indirect_function
 enable_initfini_array
 enable_comdat
+enable_fix_cortex_a53_835769
 enable_gnu_unique_object
 enable_linker_build_id
 with_long_double_128
@@ -1619,6 +1620,14 @@ Optional Features:
                           glibc systems
   --enable-initfini-array	use .init_array/.fini_array sections
   --enable-comdat         enable COMDAT group support
+
+  --enable-fix-cortex-a53-835769
+                          enable workaround for AArch64 Cortex-A53 erratum
+                          835769 by default
+  --disable-fix-cortex-a53-835769
+                          disable workaround for AArch64 Cortex-A53 erratum
+                          835769 by default
+
   --enable-gnu-unique-object
                           enable the use of the @gnu_unique_object ELF
                           extension on glibc systems
@@ -17838,7 +17847,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 17841 "configure"
+#line 17850 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -17944,7 +17953,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 17947 "configure"
+#line 17956 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -23796,6 +23805,28 @@ _ACEOF
 $as_echo "$gcc_cv_lto_plugin" >&6; }
 
 case "$target" in
+
+  aarch64*-*-*)
+    # Enable default workaround for AArch64 Cortex-A53 erratum 835769.
+    # Check whether --enable-fix-cortex-a53-835769 was given.
+if test "${enable_fix_cortex_a53_835769+set}" = set; then :
+  enableval=$enable_fix_cortex_a53_835769;
+        case $enableval in
+          yes)
+            tm_defines="${tm_defines} TARGET_FIX_ERR_A53_835769_DEFAULT=1"
+            ;;
+          no)
+            ;;
+          *)
+            as_fn_error "'$enableval' is an invalid value for --enable-fix-cortex-a53-835769.\
+  Valid choices are 'yes' and 'no'." "$LINENO" 5
+            ;;
+
+        esac
+
+fi
+
+  ;;
   # All TARGET_ABI_OSF targets.
   alpha*-*-linux* | alpha*-*-*bsd*)
     { $as_echo "$as_me:${as_lineno-$LINENO}: checking assembler for explicit relocation support" >&5
diff --git a/gcc/configure.ac b/gcc/configure.ac
index 3ee1d67..701cbf8 100644
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -3443,6 +3443,32 @@ AC_DEFINE_UNQUOTED(HAVE_LTO_PLUGIN, $gcc_cv_lto_plugin,
 AC_MSG_RESULT($gcc_cv_lto_plugin)
 
 case "$target" in
+
+  aarch64*-*-*)
+    # Enable default workaround for AArch64 Cortex-A53 erratum 835769.
+    AC_ARG_ENABLE(fix-cortex-a53-835769,
+    [
+AS_HELP_STRING([--enable-fix-cortex-a53-835769],
+        [enable workaround for AArch64 Cortex-A53 erratum 835769 by default])
+AS_HELP_STRING([--disable-fix-cortex-a53-835769],
+        [disable workaround for AArch64 Cortex-A53 erratum 835769 by default])
+    ],
+      [
+        case $enableval in
+          yes)
+            tm_defines="${tm_defines} TARGET_FIX_ERR_A53_835769_DEFAULT=1"
+            ;;
+          no)
+            ;;
+          *)
+            AC_MSG_ERROR(['$enableval' is an invalid value for --enable-fix-cortex-a53-835769.\
+  Valid choices are 'yes' and 'no'.])
+            ;;
+
+        esac
+      ],
+    [])
+  ;;
   # All TARGET_ABI_OSF targets.
   alpha*-*-linux* | alpha*-*-*bsd*)
     gcc_GAS_CHECK_FEATURE([explicit relocation support],
diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index 672d783..27c98c4 100644
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -2982,6 +2982,8 @@ information have to.
 @ifhtml
 @itemize
 @item
+@uref{#aarch64x-x-x,,aarch64*-*-*}
+@item
 @uref{#alpha-x-x,,alpha*-*-*}
 @item
 @uref{#alpha-dec-osf51,,alpha*-dec-osf5.1}
@@ -3124,6 +3126,18 @@ information have to.
 <!-- -------- host/target specific issues start here ---------------- -->
 <hr />
 @end html
+
+@heading @anchor{aarch64x-x-x}aarch64*-*-*
+To enable a workaround for the Cortex-A53 erratum number 835769 by default
+(for all CPUs regardless of -mcpu option given) at configure time use the
+@option{--enable-fix-cortex-a53-835769} option.  This will enable the fix by
+default and can be explicitly disabled during during compilation by passing the
+@option{-mno-fix-cortex-a53-835769} option.  Conversely,
+@option{--disable-fix-cortex-a53-835769} will disable the workaround by
+default.  The workaround is disabled by default if neither of
+@option{--enable-fix-cortex-a53-835769} or
+@option{--disable-fix-cortex-a53-835769} is given at configure time.
+
 @heading @anchor{alpha-x-x}alpha*-*-*
 
 This section contains general configuration information for all