unsupported inline asm: input with type 'long' matching output with type 'int'

[Quuxplusone]

Bugzilla Link	PR14408
Status	NEW
Importance	P enhancement
Reported by	Zhenbo Xu (zhenbo1987@gmail.com)
Reported on	2012-11-22 01:42:59 -0800
Last modified on	2015-08-18 20:53:36 -0700
Version	trunk
Hardware	PC Linux
CC	anton@korobeynikov.info, jtony@ca.ibm.com, llvm-bugs@lists.llvm.org, pawel@32bitmicro.com, rafael@espindo.la
Fixed by commit(s)
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clang generate error instead of warning in the following testcase.

TestCase:
static inline __attribute__((no_instrument_function)) int ffs(int x)
{
   int r;
   long tmp = -1;
   asm("bsfl %1,%0"
       : "=r" (r)
       : "rm" (x), "0" (tmp));
   return r + 1;
}

[Quuxplusone]

The error is correct per se. The code is buggy and needs to be fixed.

[Quuxplusone]

The code is from linux kernel 3.5.4. gcc don't generate this error.
(In reply to comment #1)
> The error is correct per se. The code is buggy and needs to be fixed.

[Quuxplusone]

The test case here is indeed buggy. Because it is not good to cast long to int.
However, I met a similar problem. Clang cannot cast int to long, which I think
can be improved. The test case is as follows:

void VALGRIND_PRINTF(const char *format, ...)
{
   unsigned long _qzz_res = ({
        unsigned long long  int _zzq_result;
         __asm__ volatile("lgr 3,%1"
                        : "=d" (_zzq_result)
                        : "0" (0)
                        );
         _zzq_result; });
}

error: unsupported inline asm: input with type 'int' matching output with type
'volatile unsigned long long'
                        : "0" (0)
                               ^

In this case, if we can cast 0 to unsigned long long  int, there will be no
error.