https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97528
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jakub at gcc dot gnu.org
--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
We have:
(insn 7 6 9 2 (set (reg:SI 114 [ _3 ])
(ashift:SI (reg:SI 122 [ d ])
(const_int 1 [0x1]))) "pr97528-2.c":14:9 147 {*arm_shiftsi3}
(expr_list:REG_DEAD (reg:SI 122 [ d ])
(nil)))
...
(insn 12 25 24 2 (set (mem/c:V4HI (post_modify:SI (reg/v/f:SI 118 [ dst ])
(plus:SI (reg/v/f:SI 118 [ dst ])
(reg:SI 114 [ _3 ]))) [0 MEM[(short int[4] *)&c]+0 S8 A16])
(unspec:V4HI [
(reg:V4HI 117 [ _14 ])
] UNSPEC_VST1)) "pr97528-2.c":13:5 2508 {neon_vst1v4hi}
(expr_list:REG_INC (reg/v/f:SI 118 [ dst ])
(nil)))
and combine attempts to propagate the shift into the insn:
(insn 12 25 24 2 (set (mem/c:V4HI (post_modify:SI (reg/v/f:SI 118 [ dst ])
(plus:SI (mult:SI (reg:SI 122 [ d ])
(const_int 2 [0x2]))
(reg/v/f:SI 118 [ dst ]))) [0 MEM[(short int[4] *)&c]+0 S8
A16])
(unspec:V4HI [
(reg:V4HI 117 [ _14 ])
] UNSPEC_VST1)) "pr97528-2.c":13:5 2508 {neon_vst1v4hi}
(expr_list:REG_INC (reg/v/f:SI 118 [ dst ])
(nil)))
That is not valid RTL, as documented:
Currently, the compiler can only handle second operands of the
form (plus (reg) (reg)) and (plus (reg) (const_int)), where
the first operand of the PLUS has to be the same register as
the first operand of the *_MODIFY.
