Mips specific inline asm operand modifier 'D'

Modifier 'D' is to use the second word of a double integer.

We had previously implemented the pure register varient of 
the modifier and this patch implements the memory reference.



#include "stdio.h"

int b[8] = {0,1,2,3,4,5,6,7};
void main()
{
    int i;
    
    // The first word. Notice, no 'D'
    {asm (
    "lw    %0,%1;"
    : "=r" (i)
    : "m" (*(b+4))
    );}
    
    printf("%d\n",i);

    // The second word
    {asm (
    "lw    %0,%D1;"
    : "=r" (i)
    : "m" (*(b+4))
    );}
    
    printf("%d\n",i);
}


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179135 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/Mips/MipsAsmPrinter.cpp

@@ -423,12 +423,18 @@ bool MipsAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
                                            unsigned OpNum, unsigned AsmVariant,
                                            const char *ExtraCode,
                                            raw_ostream &O) {
-  if (ExtraCode && ExtraCode[0])
-    return true; // Unknown modifier.
+  int Offset = 0;
+  // Currently we are expecting either no ExtraCode or 'D'
+  if (ExtraCode) {
+    if (ExtraCode[0] == 'D')
+      Offset = 4;
+    else
+      return true; // Unknown modifier.
+  }
 
   const MachineOperand &MO = MI->getOperand(OpNum);
   assert(MO.isReg() && "unexpected inline asm memory operand");
-  O << "0($" << MipsInstPrinter::getRegisterName(MO.getReg()) << ")";
+  O << Offset << "($" << MipsInstPrinter::getRegisterName(MO.getReg()) << ")";
 
   return false;
 }