https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65540
Jan Hubicka <hubicka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |hubicka at gcc dot gnu.org
--- Comment #9 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
OK,
hand written wrapper is produced as follows:
f3 (long double x)
{
long double _3;
<bb 2>:
_3 = func2 (x_2(D)); [return slot optimization]
<retval> = _3;
return <retval>;
}
and create_wrapper produces:
func1 (long double x)
{
long double retval.3;
<bb 2>:
retval.3_2 = func2 (x_1(D)); [return slot optimization] [tail call]
return retval.3_2;
}
I suppose it is the tail call that fails here, but I think it is just missed
optimization we do not produce it in the first case because the parameter also
needs copying:
f3:
subq $72, %rsp
.seh_stackalloc 72
.seh_endprologue
fldt (%rdx)
movq %rcx, %r8
leaq 32(%rsp), %rdx
leaq 48(%rsp), %rcx
fstpt 32(%rsp)
call func2
movq %r8, %rax
fldt 48(%rsp)
fstpt (%r8)
addq $72, %rsp
ret
compiling it as jmp func2 would definitly be an improvmeent!
We die expanding address of the first parameter:
#2 0x00000000104f6d5c in expand_expr_addr_expr_1 (exp=0x3fffaf921050,
target=target@entry=0x0, tmode=tmode@entry=DImode,
modifier=modifier@entry=EXPAND_NORMAL, as=as@entry=0 '\000')
at ../../gcc/expr.c:7761
7761 gcc_assert (inner != exp);
(gdb) p debug_tree (exp)
<ssa_name 0x3fffaf921050
type <real_type 0x3fffaf8c1500 long double XF
size <integer_cst 0x3fffaf880cf0 constant 128>
unit size <integer_cst 0x3fffaf880d08 constant 16>
align 128 symtab 0 alias set 1 canonical type 0x3fffaf8c1500 precision
80
pointer_to_this <pointer_type 0x3fffaf8c16f8>>
visited var <parm_decl 0x3fffafa80000 x>def_stmt GIMPLE_NOP
version 1>
$1 = void
Where clearly we have problem of copying it to SSA name.
I suppose code in https://gcc.gnu.org/ml/gcc-patches/2014-11/msg00423.html may
need to happen on non-aggregates, too
