re PR lto/42776 (LTO doesn't work on non-ELF platforms.)

ChangeLog:

	PR lto/42776
	* configure.ac (--enable-lto): Refactor handling so libelf tests
	are only performed inside then-clause of ACX_ELF_TARGET_IFELSE,
	and allow LTO to be explicitly enabled on non-ELF platforms that
	are known to support it inside else-clause.
	* configure: Regenerate.

gcc/ChangeLog:

	PR lto/42776
	* configure.ac (gcc_cv_as_section_has_align): Set if installed
	binutils supports extended .section directive needed by LTO, or
	warn if older binutils found.
	(LTO_BINARY_READER): New AC_SUBST'd variable.
	(LTO_USE_LIBELF): Likewise.
	* gcc/config.gcc (lto_binary_reader): New target-specific configure
	variable.
	* gcc/Makefile.in (LTO_BINARY_READER): Import AC_SUBST'd autoconf var.
	(LTO_USE_LIBELF): Likewise.
	* configure: Regenerate.

	* collect2.c (is_elf): Rename from this ...
	(is_elf_or_coff): ... to this, and recognize and allow i386 COFF
	 object files in addition to ELF-formatted ones.
	(scan_prog_file): Caller updated.  Also allow for LTO info marker
	symbol to be prefixed or not by an extra underscore.

	* config/i386/t-cygming (winnt.o): Also depend on LTO_STREAMER_H.
	* config/i386/winnt.c: Also #include lto-streamer.h
	(i386_pe_asm_named_section): Specify 1-byte section alignment for
	LTO named sections.
	(i386_pe_asm_output_aligned_decl_common): Add comment.
	(i386_pe_maybe_record_exported_symbol): Allow decl arg to be NULL.

gcc/lto/ChangeLog:

	PR lto/42776
	* Make-lang.in (LTO_OBJS): Use LTO_BINARY_READER instead of
	hardcoding 'lto-elf.o'.
	($(LTO_EXE)): Use LTO_USE_LIBELF instead of hardcoding '-lelf'.

	* lto-coff.h: New file.
	* lto-coff.c: Likewise.

gcc/testsuite/ChangeLog:

	PR lto/42776
	* lib/lto.exp (lto_prune_vis_warns): New function.
	(lto-link-and-maybe-run): Call it.

From-SVN: r158762

ChangeLog

+2010-04-27  Dave Korn  <dave.korn.cygwin@gmail.com>
+
+	PR lto/42776
+	* configure.ac (--enable-lto): Refactor handling so libelf tests
+	are only performed inside then-clause of ACX_ELF_TARGET_IFELSE,
+	and allow LTO to be explicitly enabled on non-ELF platforms that
+	are known to support it inside else-clause.
+	* configure: Regenerate.
+
 2010-04-20  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* configure.ac (BUILD_CONFIG): Redirect output to /dev/null.

configure.ac

@@ -1637,17 +1637,8 @@ AC_ARG_ENABLE(lto,
 enable_lto=$enableval,
 enable_lto=yes; default_enable_lto=yes)
 
-ACX_ELF_TARGET_IFELSE([],
-if test x"$default_enable_lto" = x"yes" ; then
-  enable_lto=no
-else
-  if test x"$enable_lto" = x"yes"; then
-    AC_MSG_ERROR([LTO support requires an ELF target.])
-  fi
-fi
-default_enable_lto=no)
 
-if test x"$enable_lto" = x"yes" ; then
+ACX_ELF_TARGET_IFELSE([if test x"$enable_lto" = x"yes" ; then
   # Make sure that libelf.h and gelf.h are available.
   AC_ARG_WITH(libelf, [  --with-libelf=PATH       Specify prefix directory for the installed libelf package
                           Equivalent to --with-libelf-include=PATH/include
@@ -1783,7 +1774,24 @@ to specify its location.])
   # Flags needed for libelf.
   AC_SUBST(libelflibs)
   AC_SUBST(libelfinc)
-fi
+fi],[if test x"$default_enable_lto" = x"yes" ; then
+    # On non-ELF platforms, LTO must be explicitly enabled.
+    enable_lto=no
+  else
+  # Apart from ELF platforms, only Windows supports LTO so far.  It
+  # would also be nice to check the binutils support, but we don't
+  # have gcc_GAS_CHECK_FEATURE available here.  For now, we'll just
+  # warn during gcc/ subconfigure; unless you're bootstrapping with
+  # -flto it won't be needed until after installation anyway.
+    case $target in
+      *-cygwin*|*-mingw*) ;;
+      *) if test x"$enable_lto" = x"yes"; then
+	AC_MSG_ERROR([LTO support is not enabled for this target.])
+        fi
+      ;;
+    esac
+  fi
+  default_enable_lto=no])
 
 
 # By default, C is the only stage 1 language.

gcc/Makefile.in

@@ -326,6 +326,10 @@ LIBELFINC = @LIBELFINC@
 # Set to 'yes' if the LTO front end is enabled.
 enable_lto = @enable_lto@
 
+# Set according to LTO object file format.
+LTO_BINARY_READER = @LTO_BINARY_READER@
+LTO_USE_LIBELF = @LTO_USE_LIBELF@
+
 # Compiler needed for plugin support
 PLUGINCC = @CC@
 

gcc/collect2.c

@@ -2548,19 +2548,21 @@ write_aix_file (FILE *stream, struct id *list)
    be in ELF format.  */
 
 static bool
-is_elf (const char *prog_name)
+is_elf_or_coff (const char *prog_name)
 {
   FILE *f;
   char buf[4];
   static char magic[4] = { 0x7f, 'E', 'L', 'F' };
+  static char coffmag[2] = { 0x4c, 0x01 };
 
-  f = fopen (prog_name, "r");
+  f = fopen (prog_name, "rb");
   if (f == NULL)
     return false;
   if (fread (buf, sizeof (buf), 1, f) != 1)
     buf[0] = 0;
   fclose (f);
-  return memcmp (buf, magic, sizeof (magic)) == 0;
+  return memcmp (buf, magic, sizeof (magic)) == 0
+	|| memcmp (buf, coffmag, sizeof (coffmag)) == 0;
 }
 
 /* Generic version to scan the name list of the loaded program for
@@ -2587,10 +2589,10 @@ scan_prog_file (const char *prog_name, scanpass which_pass,
   if (which_pass == PASS_SECOND)
     return;
 
-  /* LTO objects must be in ELF format.  This check prevents
+  /* LTO objects must be in a known format.  This check prevents
      us from accepting an archive containing LTO objects, which
      gcc cannnot currently handle.  */
-  if (which_pass == PASS_LTOINFO && !is_elf (prog_name))
+  if (which_pass == PASS_LTOINFO && !is_elf_or_coff (prog_name))
     return;
 
   /* If we do not have an `nm', complain.  */
@@ -2670,9 +2672,9 @@ scan_prog_file (const char *prog_name, scanpass which_pass,
           /* Look for the LTO info marker symbol, and add filename to
              the LTO objects list if found.  */
           for (p = buf; (ch = *p) != '\0' && ch != '\n'; p++)
-            if (ch == ' '
-		&& (strncmp (p + 1, "__gnu_lto_v1", 12) == 0)
-		&& ISSPACE (p[13]))
+            if (ch == ' '  && p[1] == '_' && p[2] == '_'
+		&& (strncmp (p + (p[3] == '_' ? 2 : 1), "__gnu_lto_v1", 12) == 0)
+		&& ISSPACE (p[p[3] == '_' ? 14 : 13]))
               {
                 add_lto_object (&lto_objects, prog_name);
 

gcc/config.gcc

@@ -200,6 +200,8 @@ default_use_cxa_atexit=no
 target_gtfiles=
 need_64bit_hwint=
 need_64bit_isa=
+# Selects the object file format reader/writer used by LTO.
+lto_binary_reader=lto-elf
 
 # Don't carry these over build->host->target.  Please.
 xm_file=
@@ -1324,6 +1326,7 @@ i[34567]86-*-pe | i[34567]86-*-cygwin*)
 		thread_file='posix'
 	fi
 	use_gcc_stdint=wrap
+	lto_binary_reader=lto-coff
 	;;
 i[34567]86-*-mingw* | x86_64-*-mingw*)
 	tm_file="${tm_file} i386/unix.h i386/bsd.h i386/gas.h dbxcoff.h i386/cygming.h i386/mingw32.h"
@@ -1391,6 +1394,7 @@ i[34567]86-*-mingw* | x86_64-*-mingw*)
 	cxx_target_objs="${cxx_target_objs} winnt-cxx.o msformat-c.o"
 	default_use_cxa_atexit=yes
 	use_gcc_stdint=wrap
+	lto_binary_reader=lto-coff
 	case ${enable_threads} in
 	  "" | yes | win32)	  thread_file='win32'
 	  tmake_file="${tmake_file} i386/t-gthr-win32"

gcc/config/i386/t-cygming

@@ -30,7 +30,7 @@ LIBGCC2_INCLUDES = -I$(srcdir)/../winsup/w32api/include
 
 winnt.o: $(srcdir)/config/i386/winnt.c $(CONFIG_H) $(SYSTEM_H) coretypes.h \
   $(TM_H) $(RTL_H) $(REGS_H) hard-reg-set.h output.h $(TREE_H) flags.h \
-  $(TM_P_H) toplev.h $(HASHTAB_H) $(GGC_H)
+  $(TM_P_H) toplev.h $(HASHTAB_H) $(GGC_H) $(LTO_STREAMER_H)
 	$(COMPILER) -c $(ALL_COMPILERFLAGS) $(ALL_CPPFLAGS) $(INCLUDES) \
 	$(srcdir)/config/i386/winnt.c
 

gcc/config/i386/winnt.c

@@ -35,6 +35,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "langhooks.h"
 #include "ggc.h"
 #include "target.h"
+#include "lto-streamer.h"
 
 /* i386/PE specific attribute support.
 
@@ -465,6 +466,12 @@ i386_pe_asm_named_section (const char *name, unsigned int flags,
         *f++ = 's';
     }
 
+  /* LTO sections need 1-byte alignment to avoid confusing the
+     zlib decompression algorithm with trailing zero pad bytes.  */
+  if (strncmp (name, LTO_SECTION_NAME_PREFIX,
+			strlen (LTO_SECTION_NAME_PREFIX)) == 0)
+    *f++ = '0';
+
   *f = '\0';
 
   fprintf (asm_out_file, "\t.section\t%s,\"%s\"\n", name, flagchars);
@@ -485,6 +492,8 @@ i386_pe_asm_named_section (const char *name, unsigned int flags,
     }
 }
 
+/* Beware, DECL may be NULL if compile_file() is emitting the LTO marker.  */
+
 void
 i386_pe_asm_output_aligned_decl_common (FILE *stream, tree decl,
 					const char *name, HOST_WIDE_INT size,
@@ -581,7 +590,8 @@ static GTY(()) struct export_list *export_head;
    these, so that we can output the export list at the end of the
    assembly.  We used to output these export symbols in each function,
    but that causes problems with GNU ld when the sections are
-   linkonce.  */
+   linkonce.  Beware, DECL may be NULL if compile_file() is emitting
+   the LTO marker.  */
 
 void
 i386_pe_maybe_record_exported_symbol (tree decl, const char *name, int is_data)
@@ -589,6 +599,9 @@ i386_pe_maybe_record_exported_symbol (tree decl, const char *name, int is_data)
   rtx symbol;
   struct export_list *p;
 
+  if (!decl)
+    return;
+
   symbol = XEXP (DECL_RTL (decl), 0);
   gcc_assert (GET_CODE (symbol) == SYMBOL_REF);
   if (!SYMBOL_REF_DLLEXPORT_P (symbol))

gcc/configure

@@ -671,6 +671,8 @@ subdirs
 slibdir
 dollar
 gcc_tooldir
+LTO_USE_LIBELF
+LTO_BINARY_READER
 enable_lto
 MAINT
 zlibinc
@@ -17092,7 +17094,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 17095 "configure"
+#line 17097 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -17198,7 +17200,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 17201 "configure"
+#line 17203 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -22942,6 +22944,48 @@ if test $gcc_cv_as_ix86_pe_secrel32 = yes; then
 $as_echo "#define HAVE_GAS_PE_SECREL32_RELOC 1" >>confdefs.h
 
 fi
+	# Test if the assembler supports the extended form of the .section
+	# directive that specifies section alignment.  LTO support uses this,
+	# but normally only after installation, so we warn but don't fail the
+	# configure if LTO is enabled but the assembler does not support it.
+	{ $as_echo "$as_me:${as_lineno-$LINENO}: checking assembler for .section with alignment" >&5
+$as_echo_n "checking assembler for .section with alignment... " >&6; }
+if test "${gcc_cv_as_section_has_align+set}" = set; then :
+  $as_echo_n "(cached) " >&6
+else
+  gcc_cv_as_section_has_align=no
+    if test $in_tree_gas = yes; then
+    if test $gcc_cv_gas_vers -ge `expr \( \( 2 \* 1000 \) + 20 \) \* 1000 + 1`
+  then gcc_cv_as_section_has_align=yes
+fi
+  elif test x$gcc_cv_as != x; then
+    echo '.section lto_test,"dr0"' > conftest.s
+    if { ac_try='$gcc_cv_as $gcc_cv_as_flags -fatal-warnings -o conftest.o conftest.s >&5'
+  { { eval echo "\"\$as_me\":${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_section_has_align=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: $gcc_cv_as_section_has_align" >&5
+$as_echo "$gcc_cv_as_section_has_align" >&6; }
+
+	if test x$gcc_cv_as_section_has_align != xyes; then
+	  case ",$enable_languages," in
+	    *,lto,*)
+	      { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: LTO for $target requires binutils >= 2.20.1, but version found appears insufficient; LTO will not work until binutils is upgraded." >&5
+$as_echo "$as_me: WARNING: LTO for $target requires binutils >= 2.20.1, but version found appears insufficient; LTO will not work until binutils is upgraded." >&2;}
+	      ;;
+	  esac
+	fi
 	;;
     esac
 
@@ -25078,6 +25122,17 @@ $as_echo "#define ENABLE_LTO 1" >>confdefs.h
 
 		    enable_lto=yes
 
+		    # LTO needs to speak the platform's object file format, and has a
+		    # number of implementations of the required binary file access APIs.
+		    # ELF is the most common, and default.  We only link libelf if ELF
+		    # is indeed the selected format.
+		    LTO_BINARY_READER=${lto_binary_reader}
+		    LTO_USE_LIBELF=-lelf
+		    if test "x$lto_binary_reader" != "xlto-elf" ; then
+		      LTO_USE_LIBELF=
+		    fi
+
+
 		    ;;
 		*) ;;
 	esac

gcc/configure.ac

@@ -3202,6 +3202,19 @@ foo:	nop
 	   rm -f conftest],
 	  [AC_DEFINE(HAVE_GAS_PE_SECREL32_RELOC, 1,
 	    [Define if your assembler and linker support 32-bit section relative relocs via '.secrel32 label'.])])
+	# Test if the assembler supports the extended form of the .section
+	# directive that specifies section alignment.  LTO support uses this,
+	# but normally only after installation, so we warn but don't fail the
+	# configure if LTO is enabled but the assembler does not support it.
+	gcc_GAS_CHECK_FEATURE([.section with alignment], gcc_cv_as_section_has_align,
+	  [2,20,1],-fatal-warnings,[.section lto_test,"dr0"])
+	if test x$gcc_cv_as_section_has_align != xyes; then
+	  case ",$enable_languages," in
+	    *,lto,*)
+	      AC_MSG_WARN([LTO for $target requires binutils >= 2.20.1, but version found appears insufficient; LTO will not work until binutils is upgraded.])
+	      ;;
+	  esac
+	fi
 	;;
     esac
 
@@ -4270,6 +4283,17 @@ changequote([,])dnl
 		    AC_DEFINE(ENABLE_LTO, 1, [Define to enable LTO support.])
 		    enable_lto=yes
 		    AC_SUBST(enable_lto)
+		    # LTO needs to speak the platform's object file format, and has a
+		    # number of implementations of the required binary file access APIs.
+		    # ELF is the most common, and default.  We only link libelf if ELF
+		    # is indeed the selected format.
+		    LTO_BINARY_READER=${lto_binary_reader}
+		    LTO_USE_LIBELF=-lelf
+		    if test "x$lto_binary_reader" != "xlto-elf" ; then
+		      LTO_USE_LIBELF=
+		    fi
+		    AC_SUBST(LTO_BINARY_READER)
+		    AC_SUBST(LTO_USE_LIBELF)
 		    ;;
 		*) ;;
 	esac

gcc/lto/ChangeLog

+2010-04-27  Dave Korn  <dave.korn.cygwin@gmail.com>
+
+	PR lto/42776
+	* Make-lang.in (LTO_OBJS): Use LTO_BINARY_READER instead of
+	hardcoding 'lto-elf.o'.
+	($(LTO_EXE)): Use LTO_USE_LIBELF instead of hardcoding '-lelf'.
+
+	* lto-coff.h: New file.
+	* lto-coff.c: Likewise.
+
 2010-04-26  Richard Guenther  <rguenther@suse.de>
 
 	* lto.c (lto_fixup_type): Deal with non-type TYPE_CONTEXT.

gcc/lto/Make-lang.in

@@ -23,7 +23,7 @@
 # The name of the LTO compiler.
 LTO_EXE = lto1$(exeext)
 # The LTO-specific object files inclued in $(LTO_EXE).
-LTO_OBJS = lto/lto-lang.o lto/lto.o lto/lto-elf.o attribs.o
+LTO_OBJS = lto/lto-lang.o lto/lto.o lto/$(LTO_BINARY_READER).o attribs.o
 LTO_H = lto/lto.h $(HASHTAB_H)
 LINKER_PLUGIN_API_H = $(srcdir)/../include/plugin-api.h
 LTO_TREE_H = lto/lto-tree.h $(LINKER_PLUGIN_API_H)
@@ -73,7 +73,7 @@ lto-warn = $(STRICT_WARN)
 
 $(LTO_EXE): $(LTO_OBJS) $(BACKEND) $(LIBDEPS)
 	$(LINKER) $(ALL_LINKERFLAGS) $(LDFLAGS) -o $@ \
-		$(LTO_OBJS) $(BACKEND) $(BACKENDLIBS) $(LIBS) -lelf
+		$(LTO_OBJS) $(BACKEND) $(BACKENDLIBS) $(LIBS) $(LTO_USE_LIBELF)
 
 # Dependencies
 lto/lto-lang.o: lto/lto-lang.c $(CONFIG_H) coretypes.h debug.h \
@@ -88,3 +88,6 @@ lto/lto.o: lto/lto.c $(CONFIG_H) $(SYSTEM_H) coretypes.h opts.h \
 	$(LTO_TAGS_H) $(LTO_STREAMER_H)
 lto/lto-elf.o: lto/lto-elf.c $(CONFIG_H) coretypes.h $(SYSTEM_H) \
 	toplev.h $(LTO_H) $(TM_H) $(LIBIBERTY_H) $(GGC_H) $(LTO_STREAMER_H)
+lto/lto-coff.o: lto/lto-coff.c $(CONFIG_H) coretypes.h $(SYSTEM_H) \
+	toplev.h $(LTO_H) $(TM_H) $(LIBIBERTY_H) $(GGC_H) $(LTO_STREAMER_H) \
+	lto/lto-coff.h

gcc/testsuite/ChangeLog

+2010-04-27  Dave Korn  <dave.korn.cygwin@gmail.com>
+
+	PR lto/42776
+	* lib/lto.exp (lto_prune_vis_warns): New function.
+	(lto-link-and-maybe-run): Call it.
+
 2010-04-26  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR tree-optimization/43904

gcc/testsuite/lib/lto.exp

@@ -16,6 +16,19 @@
 
 # Contributed by Diego Novillo <dnovillo@google.com>
 
+# Prune messages from gcc that aren't useful.
+
+proc lto_prune_vis_warns { text } {
+
+    # Many tests that use visibility will still pass on platforms that don't support it.
+    regsub -all "(^|\n)\[^\n\]*: warning: visibility attribute not supported in this configuration; ignored\[^\n\]*" $text "" text
+
+    # And any stray location lines.
+    regsub -all "(^|\n)\[^\n\]*: In function \[^\n\]*" $text "" text
+    regsub -all "(^|\n)In file included from :\[^\n\]*" $text "" text
+
+    return $text
+}
 
 # lto_init -- called at the start of each subdir of tests
 
@@ -147,6 +160,10 @@ proc lto-link-and-maybe-run { testname objlist dest optall optfile optstr } {
     # Link the objects into an executable.
     set comp_output [${tool}_target_compile "$objlist" $dest executable \
 		     "$options"]
+
+    # Prune unimportant visibility warnings before checking output.
+    set comp_output [lto_prune_vis_warns $comp_output]
+
     if ![${tool}_check_compile "$testcase $testname link" "" \
 	 $dest $comp_output] then {
 	unresolved "$testcase $testname execute $optstr"