Re: [PATCH] PR66870 PowerPC64 Enable gold linker with split stack

["Lynn A. Boger" <laboger at linux dot vnet dot ibm dot com>]

Here is my updated patch, with the changes suggested by
Ian for gcc/gospec.c and David for gcc/configure.ac.

Bootstrap built and tested on ppc64le, ppc64 multilib.

2015-09-17    Lynn Boger <laboger@linux.vnet.ibm.com>
gcc/
            PR target/66870
            config/rs6000/sysv4.h:  Define TARGET_CAN_SPLIT_STACK_64BIT
            config.in:  Set up HAVE_GOLD_ALTERNATE_SPLIT_STACK
            configure.ac:  Define HAVE_GOLD_ALTERNATE_SPLIT_STACK
            on Power based on gold linker version
            configure:  Regenerate
            gcc.c:  Add -fuse-ld=gold to STACK_SPLIT_SPEC if
            HAVE_GOLD_ALTERNATE_SPLIT_STACK defined
            go/gospec.c:  (lang_specific_driver):  Set appropriate 
split stack
            options for 64 bit compiles based on 
TARGET_CAN_SPLIT_STACK_64BIT

On 09/15/2015 02:58 PM, Ian Lance Taylor wrote:
> On Tue, Sep 15, 2015 at 11:24 AM, Lynn A. Boger
> <laboger@linux.vnet.ibm.com>  wrote:
> > I need some feedback on whether to enable the gold linker at
> > all for split stack on platforms other than Power in gcc/configure.ac.
> > I don't know if there are gold linker versions that should be verified for
> > non-Power platforms.  My first patch only enabled it on Power and that
> >   is what I think should be done.  Those who would like to use gold
> > with split stack for other platforms can enable it under the appropriate
> > conditions.
> I think that is fine for now.  If you want to enable gold for
> i386/x86_64 with -fsplit-stack, that is also fine.
>
> Ian

Index: gcc/config/rs6000/sysv4.h
===================================================================
--- gcc/config/rs6000/sysv4.h	(revision 227812)
+++ gcc/config/rs6000/sysv4.h	(working copy)
@@ -940,6 +940,14 @@ ncrtn.o%s"
 #undef TARGET_ASAN_SHADOW_OFFSET
 #define TARGET_ASAN_SHADOW_OFFSET rs6000_asan_shadow_offset
 
+/* On ppc64 and ppc64le, split stack is only support for
+   64 bit. */
+#undef TARGET_CAN_SPLIT_STACK_64BIT
+#if TARGET_GLIBC_MAJOR > 2 \
+  || (TARGET_GLIBC_MAJOR == 2 && TARGET_GLIBC_MINOR >= 18)
+#define TARGET_CAN_SPLIT_STACK_64BIT
+#endif
+
 /* This target uses the sysv4.opt file.  */
 #define TARGET_USES_SYSV4_OPT 1
 
Index: gcc/config.in
===================================================================
--- gcc/config.in	(revision 227812)
+++ gcc/config.in	(working copy)
@@ -1310,6 +1310,12 @@
 #endif
 
 
+/* Define if the gold linker with split stack is available as a non-default */
+#ifndef USED_FOR_TARGET
+#undef HAVE_GOLD_NON_DEFAULT_SPLIT_STACK
+#endif
+
+
 /* Define if you have the iconv() function. */
 #ifndef USED_FOR_TARGET
 #undef HAVE_ICONV
Index: gcc/configure.ac
===================================================================
--- gcc/configure.ac	(revision 227812)
+++ gcc/configure.ac	(working copy)
@@ -2247,6 +2247,42 @@ if test x$gcc_cv_ld != x; then
 fi
 AC_MSG_RESULT($ld_is_gold)
 
+AC_MSG_CHECKING(gold linker with split stack support as non default)
+# Check to see if default ld is not gold, but gold is
+# available and has support for split stack.  If gcc was configured
+# with gold then no checking is done.
+# 
+if test x$ld_is_gold = xno && which ${gcc_cv_ld}.gold >/dev/null 2>&1; then
+
+# For platforms other than powerpc64*, enable as appropriate.
+
+  gold_non_default=no
+  ld_gold=`which ${gcc_cv_ld}.gold`
+# Make sure this gold has minimal split stack support
+  if $ld_gold --help 2>/dev/null | grep split-stack-adjust-size >/dev/null 2>&1; then
+    ld_vers=`$ld_gold --version | sed 1q`
+    gold_vers=`echo $ld_vers | sed -n \
+          -e 's,^[[^)]]*[[  ]]\([[0-9]][[0-9]]*\.[[0-9]][[0-9]]*[[^)]]*\)) .*$,\1,p'`
+    case $target in
+# check that the gold version contains the complete split stack support
+# on powerpc64 big and little endian
+      powerpc64*-*-*)
+        case "$gold_vers" in
+          2.25.[[1-9]]*|2.2[[6-9]][[.0-9]]*|2.[[3-9]][[.0-9]]*|[[3-9]].[[.0-9]]*) gold_non_default=yes
+          ;;
+          *) gold_non_default=no
+          ;;
+        esac
+        ;;
+    esac
+  fi
+  if test $gold_non_default = yes; then
+    AC_DEFINE(HAVE_GOLD_NON_DEFAULT_SPLIT_STACK, 1,
+    	    [Define if the gold linker supports split stack and is available as a non-default])
+  fi
+fi
+AC_MSG_RESULT($gold_non_default)
+
 ORIGINAL_LD_FOR_TARGET=$gcc_cv_ld
 AC_SUBST(ORIGINAL_LD_FOR_TARGET)
 case "$ORIGINAL_LD_FOR_TARGET" in
Index: gcc/gcc.c
===================================================================
--- gcc/gcc.c	(revision 227812)
+++ gcc/gcc.c	(working copy)
@@ -666,7 +666,11 @@ proper position among the other output files.  */
    libgcc.  This is not yet a real spec, though it could become one;
    it is currently just stuffed into LINK_SPEC.  FIXME: This wrapping
    only works with GNU ld and gold.  */
+#ifdef HAVE_GOLD_NON_DEFAULT_SPLIT_STACK
+#define STACK_SPLIT_SPEC " %{fsplit-stack: -fuse-ld=gold --wrap=pthread_create}"
+#else
 #define STACK_SPLIT_SPEC " %{fsplit-stack: --wrap=pthread_create}"
+#endif
 
 #ifndef LIBASAN_SPEC
 #define STATIC_LIBASAN_LIBS \
Index: gcc/go/gospec.c
===================================================================
--- gcc/go/gospec.c	(revision 227812)
+++ gcc/go/gospec.c	(working copy)
@@ -106,6 +106,9 @@ lang_specific_driver (struct cl_decoded_option **i
   /* The total number of arguments with the new stuff.  */
   int num_args = 1;
 
+  /* Supports split stack */
+  int supports_split_stack = 0;
+
   /* Whether the -o option was used.  */
   bool saw_opt_o = false;
 
@@ -117,6 +120,9 @@ lang_specific_driver (struct cl_decoded_option **i
   /* Whether the -S option was used.  */
   bool saw_opt_S = false;
 
+  /* Whether the -m32 option was used. */
+  bool saw_opt_m32 = false;
+
   /* The first input file with an extension of .go.  */
   const char *first_go_file = NULL;  
 
@@ -152,6 +158,10 @@ lang_specific_driver (struct cl_decoded_option **i
 	    library = (library == 0) ? 1 : library;
 	  break;
 
+	case OPT_m32:
+	  saw_opt_m32 = true;
+	  break;
+
 	case OPT_pg:
 	case OPT_p:
 	  saw_profile_flag = true;
@@ -236,15 +246,22 @@ lang_specific_driver (struct cl_decoded_option **i
   /* Copy the 0th argument, i.e., the name of the program itself.  */
   new_decoded_options[j++] = decoded_options[i++];
 
+#ifdef TARGET_CAN_SPLIT_STACK
+  supports_split_stack = 1;
+#endif
+
+#ifdef TARGET_CAN_SPLIT_STACK_64BIT
+  if (!saw_opt_m32)
+    supports_split_stack = 1;
+#endif
+
   /* If we are linking, pass -fsplit-stack if it is supported.  */
-#ifdef TARGET_CAN_SPLIT_STACK
-  if (library >= 0)
+  if ((library >= 0) && supports_split_stack)
     {
       generate_option (OPT_fsplit_stack, NULL, 1, CL_DRIVER,
 		       &new_decoded_options[j]);
       j++;
     }
-#endif
 
   /* NOTE: We start at 1 now, not 0.  */
   while (i < argc)
@@ -381,19 +398,17 @@ lang_specific_driver (struct cl_decoded_option **i
     generate_option (OPT_shared_libgcc, NULL, 1, CL_DRIVER,
 		     &new_decoded_options[j++]);
 
-#ifdef TARGET_CAN_SPLIT_STACK
   /* libgcc wraps pthread_create to support split stack, however, due to
      relative ordering of -lpthread and -lgcc, we can't just mark
      __real_pthread_create in libgcc as non-weak.  But we need to link in
      pthread_create from pthread if we are statically linking, so we work-
      around by passing -u pthread_create to the linker. */
-  if (static_link)
+  if (static_link && supports_split_stack)
     {
       generate_option (OPT_Wl_, "-u,pthread_create", 1, CL_DRIVER,
 		       &new_decoded_options[j]);
       j++;
     }
-#endif
 
 #if defined(TARGET_SOLARIS) && !defined(USE_GLD)
   /* We use a common symbol for go$zerovalue.  On Solaris, when not