[LLVMbugs] [Bug 4778] New: msp430 specific: problem with constraint 'r' in inline asm

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=4778

           Summary: msp430 specific: problem with constraint 'r' in inline
                    asm
           Product: new-bugs
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: regehr at cs.utah.edu
                CC: asl at math.spbu.ru, llvmbugs at cs.uiuc.edu


For this code:

char __nesc_atomic_start(void )
{
  char result = (({
        unsigned int __x;
        __asm volatile ("mov    r2, %0" : "=r"((unsigned int)__x));__x;
      }
      )
    & 0x0008) != 0;
  __asm volatile ("dint");
  __asm volatile ("nop");
  __asm volatile ("" :  :  : "memory");
  return result;
}

We want something like this:

regehr at john-home:~/z/tinyos-2.x/apps/Null/build/telosb$ msp430-gcc small.c -Os
-S -o -
__nesc_atomic_start:
        mov     r2, r15
        clrc
        rrc     r15
        rra     r15
        rra     r15
        and.b   #llo(1), r15
        dint
        nop
        sxt     r15
        ret

But we get:

regehr at john-home:~/z/tinyos-2.x/apps/Null/build/telosb$ clang -ccc-host-triple
msp430-generic-generic -ccc-clang-archs msp430 -x c -S -w -O2 small.c
-fheinous-gnu-extensions
fatal error: error in backend: Couldn't allocate output reg for constraint 'r'!


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