Hi Denis, the new i386 memcpy macro is a ticking timebomb.
I've been debugging a new mISDN crash, just to find out that a memcpy
was not inlined correctly.
Andrew, you should drop the fix-i386-memcpy.patch (or have it fixed).
This source code:
mISDN_pid_t pid;
[...]
memcpy(&st->mgr->pid, &pid, sizeof(mISDN_pid_t));
was compiled as:
lea 0xffffffa4(%ebp),%esi <---- %esi is loaded
( add $0x10,%ebx )
( mov %ebx,%eax ) something else
( call 1613 <test_stack_protocol+0x83> ) %esi preserved
mov 0xffffffa0(%ebp),%edx
mov 0x74(%edx),%edi <---- %edi is loaded
add $0x20,%edi offset in structure added
! mov $0x14,%esi !!!!!! <---- %esi overwritten!
mov %esi,%ecx <---- %ecx loaded
repz movsl %ds:(%esi),%es:(%edi)
Apparently the compiled decided that the value 0x14 could be reused
afterwards (which it does for an inlined memset of the same size some
instructions below) and clobbers %esi.
Looking at the macro:
__asm__ __volatile__(
""
: "=&D" (edi), "=&S" (esi)
: "0" ((long) to),"1" ((long) from)
: "memory"
);
}
if (n >= 5*4) {
/* large block: use rep prefix */
int ecx;
__asm__ __volatile__(
"rep ; movsl"
: "=&c" (ecx)
it seems obvious that the compiled assumes it can reuse %esi and %edi
for something else between the two __asm__ sections. These should
probably be merged.
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