https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110701
Xi Ruoyao <xry111 at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|c |rtl-optimization
--- Comment #1 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
Combine pass seems guilty. Before combine:
(insn 21 20 23 2 (parallel [
(set (subreg:HI (reg:DI 92) 0)
(and:HI (subreg:HI (reg:DI 92) 0)
(const_int 340 [0x154])))
(clobber (reg:CC 17 flags))
]) "/app/example.c":5:39 596 {*andhi_1}
(expr_list:REG_UNUSED (reg:CC 17 flags)
(nil)))
(insn 23 21 24 2 (parallel [
(set (reg:HI 94)
(xor:HI (subreg:HI (reg:DI 92) 0)
(const_int 3 [0x3])))
(clobber (reg:CC 17 flags))
]) "/app/example.c":7:23 discrim 1 634 {*xorhi_1}
(expr_list:REG_DEAD (reg:DI 92)
(expr_list:REG_UNUSED (reg:CC 17 flags)
(nil))))
(insn 24 23 25 2 (set (reg:SI 95)
(sign_extend:SI (reg:HI 94))) "/app/example.c":7:23 discrim 1 179
{extendhisi2}
(expr_list:REG_DEAD (reg:HI 94)
(nil)))
(insn 25 24 26 2 (set (mem:SI (reg/f:DI 85 [ c.3_6 ]) [3 *c.3_6+0 S4 A32])
(reg:SI 95)) "/app/example.c":7:23 discrim 1 91 {*movsi_internal}
(expr_list:REG_DEAD (reg:SI 95)
(expr_list:REG_DEAD (reg/f:DI 85 [ c.3_6 ])
(nil))))
This is perfectly legal. After combine:
(insn 21 20 23 2 (parallel [
(set (subreg:HI (reg:DI 92) 0)
(and:HI (subreg:HI (reg:DI 92) 0)
(const_int 340 [0x154])))
(clobber (reg:CC 17 flags))
]) "/app/example.c":5:39 596 {*andhi_1}
(expr_list:REG_UNUSED (reg:CC 17 flags)
(nil)))
(note 23 21 24 2 NOTE_INSN_DELETED)
(insn 24 23 25 2 (parallel [
(set (reg:SI 95)
(ior:SI (subreg:SI (reg:DI 92) 0)
(const_int 3 [0x3])))
(clobber (reg:CC 17 flags))
]) "/app/example.c":7:23 discrim 1 635 {*iorsi_1}
(expr_list:REG_UNUSED (reg:CC 17 flags)
(expr_list:REG_DEAD (reg:DI 92)
(nil))))
(insn 25 24 26 2 (set (mem:SI (reg/f:DI 85 [ c.3_6 ]) [3 *c.3_6+0 S4 A32])
(reg:SI 95)) "/app/example.c":7:23 discrim 1 91 {*movsi_internal}
(expr_list:REG_DEAD (reg:SI 95)
(expr_list:REG_DEAD (reg/f:DI 85 [ c.3_6 ])
(nil))))
The removal of sign_extend seems wrong.
