[Bug middle-end/24969] tmpdir-gcc.dg-struct-layout-1/t026 fails execution

[rguenth at gcc dot gnu dot org]

--- Comment #4 from rguenth at gcc dot gnu dot org  2005-11-21 13:40 ---
Old value = 0
New value = 1
check2495 (arg0={a = 27121, b = {c = {d = true, e = 359101392}}}, 
arg1=0x5019ec, arg2={a = 30216, b = {c = {d = true, e = 1}}})
at t026_y.min.i:71
71   if (arg2.b.c.e != a2495[2].b.c.e) ++fails;

Reduced testcase:

void abort(void);
struct S2495 {
short int a;
union{
struct{
_Bool d;
int e:31;
} c;
} b;
};
struct S2495 x;
void foo(struct S2495 a) __attribute__((noinline));
void foo(struct S2495 a)
{
  if (a.a != x.a)
abort();
  if (a.b.c.d != x.b.c.d)
abort();
  if (a.b.c.e != x.b.c.e)
abort();
}
int main()
{
  x.a = 30216;
  x.b.c.d = 1;
  x.b.c.e = 32766;
  foo(x);
  return 0;
}


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24969

[Bug middle-end/24969] tmpdir-gcc.dg-struct-layout-1/t026 fails execution

[rguenth at gcc dot gnu dot org]

--- Comment #5 from rguenth at gcc dot gnu dot org  2005-11-21 14:06 ---
Disassembly with the first two checks removed (only the third aborts):

foo:
.LFB2:
subq$24, %rsp   #,
.LCFI0:
movlx+8(%rip), %eax #, tmp62
movl16(%rsp), %edx  #, tmp60
movq%rdi, 8(%rsp)   # a, a
andl$2147483647, %eax   #, tmp62
andl$2147483647, %edx   #, tmp60
cmpl%eax, %edx  # tmp62, tmp60
jne .L6 #,
addq$24, %rsp   #,
ret
.L6:
callabort   #

main:
.LFB3:
subq$8, %rsp#,
.LCFI1:
movlx+8(%rip), %eax #, tmp62
movw$30216, x(%rip) #, x.a
movb$1, x+4(%rip)   #, x.b.c.d
movqx(%rip), %rdi   # x, x
andl$-2147483648, %eax  #, tmp62
orl $32766, %eax#, tmp62
movl%eax, x+8(%rip) # tmp62,
callfoo #
xorl%eax, %eax  # result
addq$8, %rsp#,
ret


it looks like we are confused on where we passed the structure by value.
It's in %rdi and %eax, while we think it got passed on stack(!?) in foo.

Someone with more x86_64 ABI knowledge has to look into this.


-- 

rguenth at gcc dot gnu dot org changed:

   What|Removed |Added

 CC||hubicka at gcc dot gnu dot
   ||org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24969

[Bug middle-end/24969] tmpdir-gcc.dg-struct-layout-1/t026 fails execution

[matz at suse dot de]

--- Comment #6 from matz at suse dot de  2005-11-21 14:25 ---
Something is fishy.  Iff registers are used for passing then it would have to
be %rdi and %rsi (not %rax)!  So the high part of this struct (where the
bitfield lies) is not passed at all here.  Per ABI this whole struct
should be passed in registers (it's not larger than two eightbytes, and
both eightbytes have class INTEGER (they contain no unaligned fields or
other fancy stuff)).


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24969