[Bug lto/45375] [meta-bug] Issues with building Mozilla with LTO

[hubicka at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45375

--- Comment #112 from Jan Hubicka <hubicka at gcc dot gnu.org> 2011-09-28 13:33:03 UTC ---
OK, the problem turns out to be configure issue.  Configure script greps asm
output and with slim LTO it does not find there what it expects disabling
hidden visibilities. No surprise this leads to a performance disaster.  I use
the following hack:
diff -r 06b2977afb85 configure.in
--- a/configure.in      Fri Sep 09 23:25:02 2011 -0400
+++ b/configure.in      Wed Sep 28 15:30:56 2011 +0200
@@ -3035,7 +3035,7 @@
                   int foo __attribute__ ((visibility ("hidden"))) = 1;
 EOF
                   ac_cv_visibility_hidden=no
-                  if ${CC-cc} -Werror -S conftest.c -o conftest.s >/dev/null
2>&1; then
+                  if ${CC-cc} -Werror -S -fno-lto conftest.c -o conftest.s
>/dev/null 2>&1; then
                     if egrep '\.(hidden|private_extern).*foo' conftest.s
>/dev/null; then
                       ac_cv_visibility_hidden=yes
                     fi
@@ -3051,7 +3051,7 @@
                     int foo __attribute__ ((visibility ("default"))) = 1;
 EOF
                     ac_cv_visibility_default=no
-                    if ${CC-cc} -fvisibility=hidden -Werror -S conftest.c -o
conftest.s >/dev/null 2>&1; then
+                    if ${CC-cc} -fvisibility=hidden -Werror -S -fno-lto
conftest.c -o conftest.s >/dev/null 2>&1; then
                       if ! egrep '\.(hidden|private_extern).*foo' conftest.s
>/dev/null; then
                         ac_cv_visibility_default=yes
                       fi
@@ -3070,7 +3070,7 @@
                       int foo_default = 1;
 EOF
                       ac_cv_visibility_pragma=no
-                      if ${CC-cc} -Werror -S conftest.c -o conftest.s
>/dev/null 2>&1; then
+                      if ${CC-cc} -Werror -S -fno-lto conftest.c -o conftest.s
>/dev/null 2>&1; then
                         if egrep '\.(hidden|private_extern).*foo_hidden'
conftest.s >/dev/null; then
                           if ! egrep '\.(hidden|private_extern).*foo_default'
conftest.s > /dev/null; then
                             ac_cv_visibility_pragma=yes
@@ -3092,7 +3092,7 @@
 }
 EOF
                        ac_cv_have_visibility_class_bug=no
-                       if ! ${CXX-g++} ${CXXFLAGS} ${DSO_PIC_CFLAGS}
${DSO_LDOPTS} -S -o conftest.S conftest.c > /dev/null 2>&1 ; then
+                       if ! ${CXX-g++} ${CXXFLAGS} ${DSO_PIC_CFLAGS}
${DSO_LDOPTS} -S -fno-lto -o conftest.S conftest.c > /dev/null 2>&1 ; then
                          ac_cv_have_visibility_class_bug=yes
                        else
                          if test `egrep -c '@PLT|\\$stub' conftest.S` = 0;
then
@@ -3116,7 +3116,7 @@
 }
 EOF
                        ac_cv_have_visibility_builtin_bug=no
-                       if ! ${CC-cc} ${CFLAGS} ${DSO_PIC_CFLAGS} ${DSO_LDOPTS}
-O2 -S -o conftest.S conftest.c > /dev/null 2>&1 ; then
+                       if ! ${CC-cc} ${CFLAGS} ${DSO_PIC_CFLAGS} ${DSO_LDOPTS}
-O2 -S -fno-lto -o conftest.S conftest.c > /dev/null 2>&1 ; then
                          ac_cv_have_visibility_builtin_bug=yes
                        else
                          if test `grep -c "@PLT" conftest.S` = 0; then