struct A { unsigned long a; };
struct B { unsigned short b, c, d; };
struct B bar (unsigned long);
char *
foo (char *a, struct A *x)
{
struct B b = bar (x->a);
unsigned char c;
unsigned short d;
a[3] = ((unsigned char) (b.b % 10) + 48);
d = b.b / 10;
a[2] = ((unsigned char) (d % 10) + 48);
d = d / 10;
a[1] = ((unsigned char) (d % 10) + 48);
a[0] = ((unsigned char) ((d / 10) % 10) + 48);
a[4] = 46;
c = (unsigned char) b.c;
a[6] = (c % 10 + 48);
a[5] = ((c / 10) % 10 + 48);
a[7] = 46;
c = b.d;
a[9] = (c % 10 + 48);
a[8] = ((c / 10) % 10 + 48);
return a + 10;
}
ICEs with -O2 on x86_64-linux:
/tmp/tt.c: In function 'foo':
/tmp/tt.c:25:1: error: unable to find a register to spill in class 'AREG'
/tmp/tt.c:25:1: error: this is the insn:
(insn 82 81 83 2 /tmp/tt.c:18 (parallel [
(set (reg:HI 1 dx [170])
(mult:HI (zero_extend:HI (reg/v:QI 4 si [orig:82 c ] [82]))
(zero_extend:HI (reg:QI 2 cx [169]))))
(clobber (reg:CC 17 flags))
]) 337 {*umulqihi3_1} (expr_list:REG_UNUSED (reg:CC 17 flags)
(expr_list:REG_EQUAL (mult:HI (zero_extend:HI (reg/v:QI 4 si [orig:82 c
] [82]))
(const_int 205 [0xcd]))
(nil))))
/tmp/tt.c:25:1: internal compiler error: in spill_failure, at reload1.c:2151
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.
Worked in 3.4/4.0, ICEs from 4.1 onwards up to current trunk.
The problem seems to be in the combiner, it extremely lengthens the lifetime of
hard register (%rax):
in *.dce:
...
(insn 13 12 14 2 /tmp/tt.c:7 (parallel [
(set (reg:DI 113)
(lshiftrt:DI (reg:DI 0 ax)
(const_int 32 [0x20])))
(clobber (reg:CC 17 flags))
]) 549 {*lshrdi3_1_rex64} (expr_list:REG_DEAD (reg:DI 0 ax)
(expr_list:REG_UNUSED (reg:CC 17 flags)
(nil))))
(insn 14 13 16 2 /tmp/tt.c:7 (set (reg:HI 114)
(subreg:HI (reg:DI 113) 0)) 53 {*movhi_1} (expr_list:REG_DEAD (reg:DI
113)
(nil)))
... 49 insns ...
(insn 82 81 83 2 /tmp/tt.c:18 (parallel [
(set (reg:HI 168)
(mult:HI (zero_extend:HI (reg/v:QI 82 [ c ]))
(zero_extend:HI (reg:QI 169))))
(clobber (reg:CC 17 flags))
]) 337 {*umulqihi3_1} (expr_list:REG_UNUSED (reg:CC 17 flags)
(expr_list:REG_EQUAL (mult:HI (zero_extend:HI (reg/v:QI 82 [ c ]))
(const_int 205 [0xcd]))
(nil))))
... 18 insns ...
(insn 108 107 110 2 /tmp/tt.c:21 (set (reg/v:QI 93 [ c ])
(subreg:QI (reg:HI 114) 0)) 62 {*movqi_1} (expr_list:REG_DEAD (reg:HI
114)
(nil)))
...
in *.combine:
...
(note 13 12 14 2 NOTE_INSN_DELETED)
(note 14 13 16 2 NOTE_INSN_DELETED)
... many insns ...
(insn 82 81 83 2 /tmp/tt.c:18 (parallel [
(set (reg:HI 168)
(mult:HI (zero_extend:HI (reg/v:QI 82 [ c ]))
(zero_extend:HI (reg:QI 169))))
(clobber (reg:CC 17 flags))
]) 337 {*umulqihi3_1} (expr_list:REG_UNUSED (reg:CC 17 flags)
(expr_list:REG_EQUAL (mult:HI (zero_extend:HI (reg/v:QI 82 [ c ]))
(const_int 205 [0xcd]))
(nil))))
... many insns ...
(insn 108 107 110 2 /tmp/tt.c:21 (parallel [
(set (subreg:DI (reg/v:QI 93 [ c ]) 0)
(lshiftrt:DI (reg:DI 0 ax)
(const_int 32 [0x20])))
(clobber (reg:CC 17 flags))
]) 549 {*lshrdi3_1_rex64} (expr_list:REG_UNUSED (reg:CC 17 flags)
(expr_list:REG_DEAD (reg:DI 0 ax)
(nil))))
...
--
Summary: [4.3/4.4/4.5 Regression] Reload ICE due to combiner
extending life time of a hard register
Product: gcc
Version: 4.4.1
Status: UNCONFIRMED
Keywords: ice-on-valid-code
Severity: normal
Priority: P3
Component: rtl-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: jakub at gcc dot gnu dot org
GCC target triplet: x86_64-linux
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41646
