[llvm-bugs] [Bug 24501] New: unsupported inline asm: input with type 'int' matching output with type 'unsigned long long'

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https://llvm.org/bugs/show_bug.cgi?id=24501

            Bug ID: 24501
           Summary: unsupported inline asm: input with type 'int' matching
                    output with type 'unsigned long long'
           Product: clang
           Version: 3.4
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Frontend
          Assignee: unassignedclangbugs at nondot.org
          Reporter: jtony at ca.ibm.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

Created attachment 14747
  --> https://llvm.org/bugs/attachment.cgi?id=14747&action=edit
The test case file used to reproduce the error

This defect was first found when we try to build the open source
FFmpeg:valgrind.h.  while it builds fine with GCC, clang gives errors as
follows.

------------------------------------------------------------------------------
To reproduce:

> cat q.C
#include <valgrind/valgrind.h>

> clang q.C

In file included from q.C:1:
/usr/include/valgrind/valgrind.h:4516:47: error: unsupported inline asm: input
with type 'int' matching output with
      type 'volatile unsigned long long'
   _qzz_res = VALGRIND_DO_CLIENT_REQUEST_EXPR(0,
              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~
/usr/include/valgrind/valgrind.h:646:49: note: expanded from macro
'VALGRIND_DO_CLIENT_REQUEST_EXPR'
                    : "a" (&_zzq_args[0]), "0" (_zzq_default)    \
                                                ^
/usr/include/valgrind/valgrind.h:4554:47: error: unsupported inline asm: input
with type 'int' matching output with
      type 'volatile unsigned long long'
   _qzz_res = VALGRIND_DO_CLIENT_REQUEST_EXPR(0,
              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~
/usr/include/valgrind/valgrind.h:646:49: note: expanded from macro
'VALGRIND_DO_CLIENT_REQUEST_EXPR'
                    : "a" (&_zzq_args[0]), "0" (_zzq_default)    \
                                                ^
2 errors generated.
Error while processing q.C.
------------------------------------------------------------------------------




Because the valgrind.h is so large. I spent some time reducing it to a very
small test case (expand the macro _zzq_default, remove unrelated other parts),
which can still reproduce the above error. As follows:


------------------------------------------------------------------------------
> cat q.C
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" (/*(unsigned long long)i*/0)
                        );
         _zzq_result; });
}

> clang q.C

q.C:7:57: error: unsupported inline asm: input with type 'int' matching output
with type 'unsigned long long'
                        : "0" (/*(unsigned long long)i*/0)
                                                        ^
1 error generated.

------------------------------------------------------------------------------

If I explicitly cast 0 to unsigned long long, there will be no error. While I
agree it is dangerous to cast "unsigned long long" to "int" (bug #14408), but I
think it will be nice to make clang implicitly cast "int" to "unsigned long
long" in this case. Furthermore, it seems that only some type promotion work
need to be done in function Sema::ActOnGCCAsmStmt().

------------------------------------------------------------------------------
This bug exists in clang 3.4,3.5 and 3.6.

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