------- Comment #7 from rguenth at gcc dot gnu dot org 2007-12-11 12:50 -------
Reduced testcase:
extern "C" void abort() __attribute__ ((noreturn));
struct s
{
unsigned long long f1 : 40;
unsigned int f2 : 24;
} sv;
int main()
{
int f2;
sv.f2 = (1 << 24) - 1;
__asm__ volatile ("" : : : "memory");
++sv.f2;
f2 = sv.f2;
if (f2 != 0)
abort();
return 0;
}
it doesn't fail with the C frontend though, even though the IL before
expansion is the same:
<unnamed-unsigned:24> D.1548;
<bb 2>:
sv.f2 = 16777215;
__asm__ __volatile__("":::"memory");
D.1548 = sv.f2 + 1;
sv.f2 = D.1548;
if (D.1548 != 0)
the difference is:
(insn 13 10 14 3 t5.i:14 (set (reg/f:DI 67)
- (const:DI (plus:DI (symbol_ref:DI ("sv") <var_decl 0x2b6b88bba320 sv>)
+ (const:DI (plus:DI (symbol_ref:DI ("sv") [flags 0x2] <var_decl
0x2b2e527ee0a0 sv>)
(const_int 4 [0x4])))) -1 (nil))
(insn 14 13 15 3 t5.i:14 (set (reg:SI 69)
@@ -197,59 +185,52 @@
(const_int 8 [0x8]))
(nil)))
-(insn 16 15 17 3 t5.i:14 (parallel [
- (set (reg:SI 58 [ D.1548 ])
+(insn 16 15 18 3 t5.i:14 (parallel [
+ (set (reg:SI 58 [ D.2025 ])
(plus:SI (reg:SI 68)
(const_int 1 [0x1])))
(clobber (reg:CC 17 flags))
]) -1 (nil))
-(insn 17 16 19 3 t5.i:14 (parallel [
- (set (reg:SI 58 [ D.1548 ])
- (and:SI (reg:SI 58 [ D.1548 ])
- (const_int 16777215 [0xffffff])))
- (clobber (reg:CC 17 flags))
- ]) -1 (nil))
-
-(insn 19 17 20 3 t5.i:14 (set (reg/f:DI 71)
- (const:DI (plus:DI (symbol_ref:DI ("sv") <var_decl 0x2b6b88bba320 sv>)
+(insn 18 16 19 3 t5.i:14 (set (reg/f:DI 71)
+ (const:DI (plus:DI (symbol_ref:DI ("sv") [flags 0x2] <var_decl
0x2b2e527ee0a0 sv>)
(const_int 4 [0x4])))) -1 (nil))
-(insn 20 19 21 3 t5.i:14 (parallel [
+(insn 19 18 20 3 t5.i:14 (parallel [
(set (reg:SI 72)
- (ashift:SI (reg:SI 58 [ D.1548 ])
+ (ashift:SI (reg:SI 58 [ D.2025 ])
(const_int 8 [0x8])))
(clobber (reg:CC 17 flags))
]) -1 (nil))
...
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33887
