https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110748
--- Comment #15 from Vineet Gupta <vineetg at gcc dot gnu.org> ---
(In reply to Vineet Gupta from comment #12)
> > void znd(double *d) { *d = -0.0; }
> > void znf(float *f) { *f = -0.0; }
We need 3 set of changes to get const -0.0 working:
1. Allow expand to generate set mem const_couble -0.0
- rtx cost adj so compress_float_constant () doesn't force_const_mem ()
- riscv_legitimize_move to allow -0.0 and not force a reg
2. Allow subsequent passes to recog() this set mem const_double -0.0
- Beef up "*movdf_hardfloat_rv64" with additional condition check for -0.0
- Add a new constraint for -0.0
3. Add a splitter (for split1, not combine) to generate the int reg
On the branch devel/vineetg/optim-double-const-m0 I have double -0.0 working.
znd:
li a5,-1
slli a5,a5,63
sd a5,0(a0)
ret
There's currently an ICE for zbs
IRA is undoing the split so the insn with const_int 0x80000000_00000000 doesn't
exist for final pass.
expand
------
(insn 6 3 0 2 (set (mem:DF (reg:DI 135)
(const_double:DF -0.0 [-0x0.0p+0])) {*movdf_hardfloat_rv64}
split1
-----
(insn 10 3 11 2 (set (reg:DI 136)
(const_int [0x8000000000000000]))
(insn 11 10 0 2 (set (mem:DF (reg:DI 135)
(subreg:DF (reg:DI 136) 0))
ira
----
(insn 11 9 12 2 (set (mem:DF (reg:DI 135)
(const_double:DF -0.0 [-0x0.0p+0])) {*movdf_hardfloat_rv64}
