Snippet of shell session demonstrates how compiler generates bad asm (compare
to result of compilation without -DBUG). Toolchain built using latest
"crosstool" scripts.
Sample code attached below.
[EMAIL PROTECTED]:~/tools.k42/powerpc/partDeb/os$ powerpc64-linux-g++ -c -o
workqueue.o wq.C -O1 -DBUG
[EMAIL PROTECTED]:~/tools.k42/powerpc/partDeb/os$ powerpc64-linux-objdump -d
workqueue.o
workqueue.o: file format elf64-powerpc
Disassembly of section .text:
0000000000000000 <._Z10queue_workP16workqueue_structP11work_struct>:
0: 7c 08 02 a6 mflr r0
4: f8 01 00 10 std r0,16(r1)
8: f8 21 ff 91 stdu r1,-112(r1)
c: 7d a9 6b 78 mr r9,r13
10: e9 29 00 00 ld r9,0(r9)
14: 88 09 00 03 lbz r0,3(r9)
18: 2f a0 00 00 cmpdi cr7,r0,0
1c: 40 be 00 10 bne+ cr7,2c
<._Z10queue_workP16workqueue_structP11work_struct+0x2c>
20: 48 00 00 01 bl 20
<._Z10queue_workP16workqueue_structP11work_struct+0x20>
24: 60 00 00 00 nop
28: 48 00 00 00 b 28
<._Z10queue_workP16workqueue_structP11work_struct+0x28>
2c: 48 00 00 00 b 2c
<._Z10queue_workP16workqueue_structP11work_struct+0x2c>
30: 00 00 00 00 .long 0x0
34: 00 09 00 01 .long 0x90001
38: 80 00 00 00 lwz r0,0(0)
[EMAIL PROTECTED]:~/tools.k42/powerpc/partDeb/os$ powerpc64-linux-g++ -v
Reading specs from
/opt/crosstool/powerpc64-linux/gcc-3.4.2-glibc-2.3.3/lib/gcc/powerpc64-linux/3.4.2/specs
Configured with:
/home/mostrows/tools/crosstool-0.28-rc37/build/powerpc64-linux/gcc-3.4.2-glibc-2.3.3/gcc-3.4.2/configure
--target=powerpc64-linux --host=powerpc64-host_unknown-linux-gnu
--prefix=/opt/crosstool/powerpc64-linux/gcc-3.4.2-glibc-2.3.3 --disable-multilib
--with-sysroot=/opt/crosstool/powerpc64-linux/gcc-3.4.2-glibc-2.3.3/powerpc64-linux/sys-root
--with-local-prefix=/opt/crosstool/powerpc64-linux/gcc-3.4.2-glibc-2.3.3/powerpc64-linux/sys-root
--disable-nls --enable-threads=posix --enable-symvers=gnu --enable-__cxa_atexit
--enable-languages=c,c++ --enable-shared --enable-c99 --enable-long-long
Thread model: posix
gcc version 3.4.2
struct LinuxVPInfo_s {
unsigned long physProc;
};
typedef struct LinuxVPInfo_s LinuxVPInfo;
extern LinuxVPInfo linuxVPInfo;
struct cpu_workqueue_struct {
int x;
};
struct workqueue_struct {
struct cpu_workqueue_struct cpu_wq[32];
};
struct work_struct {
unsigned long pending;
void (*func)(void *);
void *data;
void *wq_data;
};
extern void __k42_spin_lock_irqsave(struct cpu_workqueue_struct* c,
unsigned long *x);
struct thread_info {
int preempt_count;
};
extern int test_and_set_bit(int x, unsigned long *y);
#ifdef BUG
static inline struct thread_info *current_thread_info(void)
__attribute__((const));
static int smp_processor_id(void) __attribute__((pure));
#else
static int smp_processor_id(void);
static inline struct thread_info *current_thread_info(void);
#endif
static __inline__ int smp_processor_id(void) {
return linuxVPInfo.physProc;
}
static inline struct thread_info *current_thread_info(void)
{
struct thread_info **ti;
__asm__("mr %0,13" : "=r"(ti));
return *ti;
}
#define cti current_thread_info
extern void lkBreakpoint(int line, const char* file, const char* fn);
extern void __k42disable_preempt();
extern void __k42enable_preempt();
int queue_work(struct workqueue_struct *wq, struct work_struct *work)
{
unsigned long flags;
int ret = 0;
int cpu = ({ do {
do {
if (((cti()->preempt_count) & (((1UL << (8))-1) << 0))==0) {
__k42disable_preempt();
(cti()->preempt_count)++;
} else
(cti()->preempt_count)++;
} while (0);
__asm__ __volatile__("": : :"memory");
} while (0);
smp_processor_id();
});
struct cpu_workqueue_struct *cwq = wq->cpu_wq + cpu;
if (!test_and_set_bit(0, &work->pending)) {
do {
if ((!work->wq_data)) {
lkBreakpoint(103,"workqueue.C",(__func__));
}
} while (0);
work->wq_data = cwq;
__k42_spin_lock_irqsave(cwq, &flags);
ret = 1;
}
do {
do {
__asm__ __volatile__("": : :"memory");
do {
if (((cti()->preempt_count) & (((1UL << (8))-1) << 0))==1) {
(cti()->preempt_count)--;
__k42enable_preempt();
} else
(cti()->preempt_count)--;
} while (0);
} while (0);
} while (0);
return ret;
}
--
Summary: const/pure functions result in bad asm
Product: gcc
Version: 3.4.2
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: mostrows at watson dot ibm dot com
CC: gcc-bugs at gcc dot gnu dot org
GCC build triplet: ppc64-linux-gnu
GCC host triplet: ppc-linux-gnu
GCC target triplet: ppc64-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17972
