[Bug lto/49286] New: LTO incompatible with PIC and inline asm

[emil.langrock at gmx dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49286

           Summary: LTO incompatible with PIC and inline asm
           Product: gcc
           Version: 4.6.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: lto
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: emil.langrock@gmx.de


Created attachment 24435
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24435
Minimal example

I have a library which needs to be compiled as PIC (amd64). It has different
parts which cannot be written in C and thus uses inline assembly. Other parts
can benefit extremely by using LTO (~10% faster and ~10% size reduction). By
default it is compiled using something like that:


$ gcc -g -O2 -fPIC -DPIC -o test.o -c test.c
$ gcc -fPIC -shared test.o -o test.so

This works perfectly. It will produce an PIC error when compiling it with LTO:


$ gcc -flto -g -O2 -fPIC -DPIC -o test.o -c test.c
$ gcc -flto -g -O2 -fPIC -DPIC -shared test.o -o test.so
/usr/bin/ld: /tmp/ccMYQCew.ltrans0.ltrans.o: relocation R_X86_64_PC32 against
undefined symbol `evil_long' can not be used when making a shared object;
recompile with -fPIC
/usr/bin/ld: final link failed: Bad value
collect2: ld returned 1 exit status


To the version I use:

Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.6.1/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.6.0-11'
--with-bugurl=file:///usr/share/doc/gcc-4.6/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++,go --prefix=/usr
--program-suffix=-4.6 --enable-shared --enable-multiarch
--with-multiarch-defaults=x86_64-linux-gnu --enable-linker-build-id
--with-system-zlib --libexecdir=/usr/lib --without-included-gettext
--enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.6
--libdir=/usr/lib --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-plugin --enable-objc-gc
--with-arch-32=i586 --with-tune=generic --enable-checking=release
--build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.6.1 20110604 (prerelease) (Debian 4.6.0-11) 
COMPILER_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.6.1/:/usr/lib/gcc/x86_64-linux-gnu/4.6.1/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/4.6.1/:/usr/lib/gcc/x86_64-linux-gnu/
LIBRARY_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.6.1/:/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../lib/:/lib/../lib/:/usr/lib/../lib/:/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-mtune=generic' '-march=x86-64'
 /usr/lib/gcc/x86_64-linux-gnu/4.6.1/collect2 --build-id --no-add-needed
--eh-frame-hdr -m elf_x86_64 --hash-style=both -dynamic-linker
/lib64/ld-linux-x86-64.so.2
/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../lib/crt1.o
/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../lib/crti.o
/usr/lib/gcc/x86_64-linux-gnu/4.6.1/crtbegin.o
-L/usr/lib/gcc/x86_64-linux-gnu/4.6.1
-L/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../lib -L/lib/../lib
-L/usr/lib/../lib -L/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../.. --version
-lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s
--no-as-needed /usr/lib/gcc/x86_64-linux-gnu/4.6.1/crtend.o
/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../lib/crtn.o
collect2 version 4.6.1 20110604 (prerelease) (x86-64 Linux/ELF)
/usr/bin/ld --build-id --no-add-needed --eh-frame-hdr -m elf_x86_64
--hash-style=both -dynamic-linker /lib64/ld-linux-x86-64.so.2
/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../lib/crt1.o
/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../lib/crti.o
/usr/lib/gcc/x86_64-linux-gnu/4.6.1/crtbegin.o
-L/usr/lib/gcc/x86_64-linux-gnu/4.6.1
-L/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../lib -L/lib/../lib
-L/usr/lib/../lib -L/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../.. --version
-lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s
--no-as-needed /usr/lib/gcc/x86_64-linux-gnu/4.6.1/crtend.o
/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../lib/crtn.o
GNU ld (GNU Binutils for Debian) 2.21.51.20110523
Copyright 2011 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License version 3 or (at your option) a later version.
This program has absolutely no warranty