Richard Sandiford <richard.sandif...@linaro.org>
> The "?" change seems to make intrinsic sense given the extra cost of the
> GPR alternative. But I think the real reason for this failure is that
> we define no V1DF patterns, and target-independent code falls back to
> using moves in the corresponding *integer* mode. So for that function
> we generate the rather ugly code:
This:
typedef struct { double x; } X;
X f2(X *p)
{
return *p;
}
emits at expand:
(insn 6 3 7 2 (set (reg:DF 90 [ D.21009 ])
(mem:DF (reg/v/f:DI 92 [ p ]) [2 *p_2(D)+0 S8 A64]))
"vect_copy_lane_1.c":26 -1
(nil))
(insn 7 6 8 2 (set (subreg:DF (reg:DI 94) 0)
(reg:DF 90 [ D.21009 ])) "vect_copy_lane_1.c":26 -1
(nil))
(insn 8 7 9 2 (set (reg:DI 95)
(reg:DI 94)) "vect_copy_lane_1.c":26 -1
(nil))
(insn 9 8 13 2 (set (reg:DF 91 [ <retval> ])
(subreg:DF (reg:DI 95) 0)) "vect_copy_lane_1.c":26 -1
(nil))
So the underlying cause is the structure passing code. Things get worse when
you return
2 doubles and it really becomes horrific at 3...
Wilco
