[Bug lto/47181] New: memops-asm testcase fails with -flto -fuse-linker-plugin

[hubicka at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47181

           Summary: memops-asm testcase fails with -flto
                    -fuse-linker-plugin
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: lto
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: hubicka@gcc.gnu.org


memops-asm testcase fails with -flto -fuse-linker-plugin. We produce undefined
call to my_memcpy:
evans:/abuild/jh/trunk-3/build-inst2/gcc/:[0]# ./xgcc -B ./ -O2 memops-asm*.c 
/abuild/jh/trunk-3/gcc/testsuite/gcc.c-torture/execute/builtins/lib/main.c  -g
-O0 -flto --save-temps -fdump-ipa-all-details    -save-temps
memops-asm.c: In function ?main_test?:
memops-asm.c:37:3: warning: incompatible implicit declaration of built-in
function ?printf? [enabled by default]
[Leaving LTRANS /tmp/ccrBB4II.args]
[Leaving LTRANS /tmp/ccc7Rjx0.ltrans.out]
[Leaving LTRANS /tmp/ccOzcZ98.args]
[Leaving LTRANS /tmp/ccc7Rjx0.ltrans0.o]
evans:/abuild/jh/trunk-3/build-inst2/gcc/:[0]# grep memcpy *.s
ccc7Rjx0.ltrans0.s:     .globl  memcpy
ccc7Rjx0.ltrans0.s:     .type   memcpy, @function
ccc7Rjx0.ltrans0.s:memcpy:
ccc7Rjx0.ltrans0.s:     call    my_memcpy.2055
ccc7Rjx0.ltrans0.s:     .size   memcpy, .-memcpy
ccc7Rjx0.ltrans0.s:     .type   my_memcpy.2055, @function
ccc7Rjx0.ltrans0.s:my_memcpy.2055:
ccc7Rjx0.ltrans0.s:     .size   my_memcpy.2055, .-my_memcpy.2055
ccc7Rjx0.ltrans0.s:     call    my_memcpy
ccc7Rjx0.ltrans0.s:     call    my_memcpy
ccc7Rjx0.ltrans0.s:     .string "memcpy"
ccc7Rjx0.ltrans0.s:     .string "my_memcpy"

the issue is that my_memcpy is declared once as:
extern void *memcpy (void *, const void *, size_t)
  __asm (ASMNAME ("my_memcpy"));
and in the other unit as
void *
my_memcpy (void *d, const void *s, size_t n)

we fail to merge the declarations in lto-symtab since builtins are streamed in
special way.  This leads to linker bug and wrong code:
http://sourceware.org/bugzilla/show_bug.cgi?id=12365