https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67124
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|target |rtl-optimization
--- Comment #12 from Richard Biener <rguenth at gcc dot gnu.org> ---
Hmm, indeed we fail to preserve the (subreg:DI (reg:TI xmm0)) in LRA
(insn 53 52 16 2 (set (reg:DI 21 xmm0 [orig:90 c ] [90])
(mem/c:DI (plus:DI (reg/f:DI 7 sp)
(const_int 8 [0x8])) [0 %sfp+-8 S8 A64])) t.c:16 85
{*movdi_internal}
(nil))
...
(insn 17 16 49 2 (set (reg:V8HI 21 xmm0 [100])
(vec_merge:V8HI (vec_duplicate:V8HI (reg:HI 0 ax [99]))
(reg:V8HI 21 xmm0 [orig:90 c ] [90])
(const_int 4 [0x4]))) t.c:16 3597 {sse2_pinsrw}
(nil))
from
(insn 15 14 16 2 (parallel [
(set (subreg:DI (reg/v:TI 90 [ c ]) 0)
(ior:DI (reg:DI 97)
(reg:DI 95)))
(clobber (reg:CC 17 flags))
]) t.c:16 398 {*iordi_1}
(expr_list:REG_DEAD (reg:DI 97)
(expr_list:REG_DEAD (reg:DI 95)
(expr_list:REG_UNUSED (reg:CC 17 flags)
(nil)))))
...
(insn 17 16 49 2 (set (reg:V8HI 100)
(vec_merge:V8HI (vec_duplicate:V8HI (subreg:HI (reg:DI 99) 0))
(subreg:V8HI (reg/v:TI 90 [ c ]) 0)
(const_int 4 [0x4]))) t.c:16 3597 {sse2_pinsrw}
A plain DImode move to a DImode reg does not preserve the upper halves. Not
sure if
(insn 53 52 16 2 (set (subreg:DI (reg:TI xmm0 0) [orig:90 c ] [90])
(mem/c:DI (plus:DI (reg/f:DI 7 sp)
(const_int 8 [0x8])) [0 %sfp+-8 S8 A64])) t.c:16 85
{*movdi_internal}
(nil))
would be valid after "reload" though.
Maybe the bug is that we allocate a DImode register to a subreg of a TImode
destination at all.
