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);
}

llvm-svn: 179135

llvm/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;
 }

llvm/test/CodeGen/Mips/inlineasmmemop.ll

@@ -1,5 +1,6 @@
 ; RUN: llc -march=mipsel < %s | FileCheck %s
 
+; Simple memory
 @g1 = external global i32
 
 define i32 @f1(i32 %x) nounwind {
@@ -21,3 +22,19 @@ entry:
   ret i32 %0
 }
 
+; "D": Second word of double word. This works for any memory element.
+; CHECK: #APP
+; CHECK-NEXT: lw ${{[0-9]+}},4(${{[0-9]+}});
+; CHECK-NEXT: #NO_APP
+
+@b = common global [20 x i32] zeroinitializer, align 4
+
+define void @main() #0 {
+entry:
+  tail call void asm sideeffect "    lw    $0,${1:D};", "r,*m,~{$11}"(i32 undef, i32* getelementptr inbounds ([20 x i32]* @b, i32 0, i32 3)) #1
+  ret void
+}
+
+attributes #0 = { nounwind "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf"="true" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind }
+