Consider:
char buf[128];
extern void bar (int a, const char *p);
extern char *strcpy (char *, const char *);
void
foo (int a)
{
if (a)
bar (0, buf);
strcpy (buf, "0123456789abcdefghijklmnopqrstuvwxyz");
bar (0, buf);
}
Compile this testcase with arm-none-linux-gnueabi-4.4.
strcpy above is inlined and unrolled like so:
ldmia r4!, {r0, r1, r2, r3}
stmia ip!, {r0, r1, r2, r3}
ldmia r4!, {r0, r1, r2, r3}
stmia ip!, {r0, r1, r2, r3}
ldmia r4, {r0, r1}
str r0, [ip], #4
mov r1, ip
strb r1, [r1], #-36
Notice that the last instruction looks strange. R1 immediately after
the last ldmia contains the last character, namely the null
terminator, but that gets destroyed in "mov r1, ip". Then strb
attempts to write r1 to the memory location pointed to by r1, which
doesn't make sense.
The last instruction comes from auto-inc-dec.c.
I've got a patch in testing.
--
Summary: auto-inc-dec generates an invalid assembly instruction
Product: gcc
Version: 4.4.4
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: rtl-optimization
AssignedTo: kazu at gcc dot gnu dot org
ReportedBy: kazu at gcc dot gnu dot org
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: arm-none-linux-gnueabi
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44404
