The following testcase is miscompiled on {powerpc,i386,x86_64}-redhat-linux
(well, any other for which an __asm is written).
extern void abort (void);
unsigned short v = 0x0300;
void
foo (unsigned short *p)
{
*p = v;
}
int
bar (void)
{
unsigned short x;
volatile unsigned short *z;
foo (&x);
const unsigned int y = x;
z = &x;
#ifdef __powerpc__
__asm __volatile ("sthbrx %1,0,%2" : "=m" (*z) : "r" (y), "r" (z));
#elif defined __i386__ || defined __x86_64__
__asm __volatile ("movb %b1,1(%2); movb %h1,(%2)" : "=m" (*z) : "r" (y), "r"
(z));
#endif
return (x & 1) == 0;
}
int
main (void)
{
if (bar ())
abort ();
return 0;
}
In final_cleanup, bar is:
bar ()
{
const unsigned intD.3 yD.1507;
short unsigned intD.8 xD.1505;
# BLOCK 0
# PRED: ENTRY [100.0%] (fallthru,exec)
# xD.1505_11 = V_MAY_DEF <xD.1505_1>;
foo (&xD.1505);
yD.1507 = (const unsigned intD.3) xD.1505;
# xD.1505_12 = V_MAY_DEF <xD.1505_11>;
__asm__ __volatile__("movb %b1,1(%2); movb %h1,(%2)":"=m" xD.1505:"r" yD.1507,
"r" &xD.1505);
return (intD.0) (yD.1507 ^ 1) & 1;
# SUCC: EXIT [100.0%]
}
which is wrong, it must reread xD.1505 instead of assuming xD.1505 == yD.1507.
--
Summary: asm "=m" not taken into account
Product: gcc
Version: 4.0.0
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: jakub at gcc dot gnu dot org
CC: gcc-bugs at gcc dot gnu dot org,mikpe at csd dot uu dot
se
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20210
