https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51840
Kai Tietz <ktietz at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2014-06-18
CC| |ktietz at gcc dot gnu.org
Ever confirmed|0 |1
--- Comment #5 from Kai Tietz <ktietz at gcc dot gnu.org> ---
So original issue is caused by two issues.
For initial expand we produce the following rtl for the first code-switch:
(jump_insn 32 31 34 2 (parallel [
(asm_operands/v ("jmp *%0") ("") 0 [
(mem/v/f/j:DI (plus:DI (mult:DI (reg:DI 136)
(const_int 8 [0x8]))
(reg/f:DI 135)) [0 vm_dispatch S8 A64])
]
[
(asm_input:DI ("m") t_asmgoto.c:65)
]
[
(label_ref:DI 36)
(label_ref:DI 56)
(label_ref:DI 114)
(label_ref:DI 120)
] t_asmgoto.c:65)
(clobber (reg:QI 18 fpsr))
(clobber (reg:QI 17 flags))
(clobber (mem:BLK (scratch) [0 A8]))
]) t_asmgoto.c:65 -1
(insn_list:REG_LABEL_TARGET 36 (insn_list:REG_LABEL_TARGET 56
(insn_list:REG_LABEL_TARGET 114 (nil))))
-> 120)
(note 34 32 33 4 [bb 4] NOTE_INSN_BASIC_BLOCK)
(note/s 33 34 35 4 ("atop__a_dec") NOTE_INSN_DELETED_LABEL 2)
(barrier 35 33 36)
(code_label 36 35 37 5 8 "" [3 uses])
...
Of interest is here the '(note/s 33 34 35 4 ("atop__a_dec")
NOTE_INSN_DELETED_LABEL 2)'. As long as code_label 36 (which is implementation
of "atop__a_dec" code) follows directly that note, we are fine.
That's true for -Os, -O0, and -O1. For -O2 we exectute additional the
basic-block-reorder pass, and that moves label 36 away. Nevertheless the
semi-deleted label-note remains and cause the wrong code-path.
