Add support for the 'N' inline asm constraint.

Patch by Jack Carter.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156284 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/Mips/MipsISelLowering.cpp b/lib/Target/Mips/MipsISelLowering.cpp
index 3f445a0..ded6aa0 100644
--- a/lib/Target/Mips/MipsISelLowering.cpp
+++ b/lib/Target/Mips/MipsISelLowering.cpp
@@ -3043,6 +3043,7 @@
   case 'J': // integer zero
   case 'K': // unsigned 16 bit immediate
   case 'L': // signed 32 bit immediate where lower 16 bits are 0
+  case 'N': // immediate in the range of -65535 to -1 (inclusive)
     if (isa<ConstantInt>(CallOperandVal))
       weight = CW_Constant;
     break;
@@ -3135,6 +3136,16 @@
       }
     }
     return;
+  case 'N': // immediate in the range of -65535 to -1 (inclusive)
+    if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op)) {
+      EVT Type = Op.getValueType();
+      int64_t Val = C->getSExtValue();
+      if ((Val >= -65535) && (Val <= -1)) {
+        Result = DAG.getTargetConstant(Val, Type);
+        break;
+      }
+    }
+    return;
   }
 
   if (Result.getNode()) {