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[Bug middle-end/26316] New: loop-invariant miscompiles openmp.c
- From: "jakub at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 16 Feb 2006 10:51:52 -0000
- Subject: [Bug middle-end/26316] New: loop-invariant miscompiles openmp.c
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
__attribute__ ((noinline))
void
bar (int i)
{
asm volatile ("" : : "r" (i));
}
struct S
{
int v;
struct S *w;
};
__attribute__ ((noinline))
void
foo (struct S *s, int l)
{
for (; s; s = s->w)
{
if (s->v && (l < 6 || l > 17))
bar (1);
switch (l)
{
case 6:
case 7:
case 8:
bar (2);
break;
case 9:
case 10:
bar (3);
break;
case 13:
case 14:
bar (4);
break;
case 17:
bar (5);
break;
default:
break;
}
}
}
int
main (void)
{
struct S s = { 0, 0 };
foo (&s, 0);
return 0;
}
is miscompiled on x86_64 at -O1 and above. Before *r.loop2_invariant dump
(insn 30 29 31 6 o.i:22 (parallel [
(set (reg:SI 61)
(plus:SI (reg/v:SI 59 [ l ])
(const_int -6 [0xfffffffffffffffa])))
(clobber (reg:CC 17 flags))
]) 208 {*addsi_1} (nil)
(nil))
(insn 31 30 32 6 o.i:22 (set (reg:CC 17 flags)
(compare:CC (reg:SI 61)
(const_int 11 [0xb]))) 5 {*cmpsi_1_insn} (nil)
(nil))
(jump_insn 32 31 85 6 o.i:22 (set (pc)
(if_then_else (gtu (reg:CC 17 flags)
(const_int 0 [0x0]))
(label_ref 70)
(pc))) 511 {*jcc_1} (nil)
(expr_list:REG_BR_PROB (const_int 5000 [0x1388])
(nil)))
(insn 33 85 35 7 o.i:22 (set (reg:DI 62)
(zero_extend:DI (reg:SI 61))) 111 {zero_extendsidi2_rex64} (nil)
(nil))
(insn 35 33 36 7 o.i:22 (set (reg:DI 64)
(mem/u/c:DI (plus:DI (mult:DI (reg:DI 62)
(const_int 8 [0x8]))
(label_ref:DI 38)) [0 S8 A8])) 81 {*movdi_1_rex64} (nil)
(insn_list:REG_LABEL 38 (nil)))
(jump_insn 36 35 41 7 o.i:22 (parallel [
(set (pc)
(reg:DI 64))
(use (label_ref 38))
]) 530 {*tablejump_1_rtx64} (nil)
(nil))
so insn 35 isn't executed if (unsigned int) (l - 6) > 11.
But in *r.loop2_invariant dump this becomes:
(insn 19 13 33 3 o.i:20 (parallel [
(set (reg:SI 65)
(plus:SI (reg/v:SI 59 [ l ])
(const_int -6 [0xfffffffffffffffa])))
(clobber (reg:CC 17 flags))
]) 208 {*addsi_1} (nil)
(nil))
(insn 33 19 35 3 o.i:22 (set (reg:DI 66)
(zero_extend:DI (reg:SI 65))) 111 {zero_extendsidi2_rex64} (nil)
(nil))
(insn 35 33 92 3 o.i:22 (set (reg:DI 67)
(mem/u/c:DI (plus:DI (mult:DI (reg:DI 66)
(const_int 8 [0x8]))
(label_ref:DI 38)) [0 S8 A8])) 81 {*movdi_1_rex64} (nil)
(insn_list:REG_LABEL 38 (nil)))
--
Summary: loop-invariant miscompiles openmp.c
Product: gcc
Version: 4.2.0
Status: UNCONFIRMED
Severity: critical
Priority: P3
Component: middle-end
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=26316