https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116550
Bug ID: 116550
Summary: [lra][avr] internal compiler error: in
final_scan_insn_1, at final.cc:2807
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: gjl at gcc dot gnu.org
Target Milestone: ---
Created attachment 59030
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=59030&action=edit
lra-bug3.c: C test case from libgcc
$ avr-gcc lra-bug3.c -mmcu=avr25 -Os -S -mlra -fnon-call-exceptions
lra-bug3.c: In function '__divmoddi4':
lra-bug3.c:214:1: error: could not split insn
214 | }
| ^
(insn 528 1670 1671 (parallel [
(set (reg/v:SI 24 r24 [orig:146 __q1 ] [146])
(plus:SI (reg/v:SI 24 r24 [orig:146 __q1 ] [146])
(const_int -2 [0xfffffffffffffffe])))
(clobber (mem/c:QI (plus:HI (reg/f:HI 28 r28)
(const_int 33 [0x21])) [6 %sfp+33 S1 A8]))
]) "lra-bug3.c":163:405 discrim 7 186 {addsi3}
(nil))
during RTL pass: final
dump file: lra-bug3.c.357r.final
lra-bug3.c:214:1: internal compiler error: in final_scan_insn_1, at
final.cc:2807
That insn is invalid, of course. With -da, the .ira dump reads:
(insn 500 499 501 65 (parallel [
(set (reg/v:SI 146 [ __q1 ])
(plus:SI (reg/v:SI 146 [ __q1 ])
(const_int -2 [0xfffffffffffffffe])))
(clobber (scratch:QI))
]) "lra-bug3.c":163:405 discrim 7 186 {addsi3}
(nil))
so everything is fine (at least as far as the dump goes). .reload has then:
(insn 1393 499 500 89 (set (reg/v:SI 18 r18 [orig:146 __q1 ] [146])
(mem/c:SI (plus:HI (reg/f:HI 28 r28)
(const_int 33 [0x21])) [6 %sfp+33 S4 A8])) "lra-bug3.c":163:405
discrim 7 119 {*movsi_split}
(nil))
(insn 500 1393 1394 89 (parallel [
(set (reg/v:SI 18 r18 [orig:146 __q1 ] [146])
(plus:SI (reg/v:SI 18 r18 [orig:146 __q1 ] [146])
(const_int -2 [0xfffffffffffffffe])))
(clobber (mem/c:QI (plus:HI (reg/f:HI 28 r28)
(const_int 33 [0x21])) [6 %sfp+33 S1 A8]))
]) "lra-bug3.c":163:405 discrim 7 186 {addsi3}
(nil))
As it seems, R146 has been spilled to FP+33, and insn 1393 is loading it to
R18. The clobber operand looks like a colateral damage. FYI, the insn reads:
;; "addsi3"
;; "addsq3" "addusq3"
;; "addsa3" "addusa3"
(define_insn_and_split "add<mode>3"
[(set (match_operand:ALL4 0 "register_operand" "=??r,d ,r")
(plus:ALL4 (match_operand:ALL4 1 "register_operand" "%0,0 ,0")
(match_operand:ALL4 2 "nonmemory_operand" "r,i ,n Ynn")))
(clobber (match_scratch:QI 3 "=X,X ,&d"))]
""
"#"
"&& reload_completed"
...)
A QImode scratch is only required when op0 ends up in a non-d register (REGNO <
16), hence the 2nd alternatice should match and op3 = scratch:QI.
This ICE is relatively new; I don't see it with "gcc version 15.0.0 20240818".
Target: avr
Configured with: ../../source/gcc-master/configure --target=avr --disable-nls
--with-dwarf2 --with-gnu-as --with-gnu-ld --disable-shared
--with-long-double=64 --enable-languages=c,c++
gcc version 15.0.0 20240831 (experimental) (GCC)
