Emit diagnostic if an inline asm constraint requires an immediate

Summary:
An inline asm call can result in an immediate after inlining. Therefore emit a
diagnostic here if constraint requires an immediate but one isn't supplied.

Reviewers: joerg, mgorny, efriedma, rsmith

Reviewed By: joerg

Subscribers: asb, rbar, johnrusso, simoncook, apazos, sabuasal, niosHD, zzheng, edward-jones, rogfer01, MartinMosbeck, brucehoult, the_o, PkmX, jocewei, s.egerton, MaskRay, jyknight, dylanmckay, javed.absar, fedor.sergeev, jrtc27, Jim, krytarowski, eraman, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60942

llvm-svn: 367750
diff --git a/llvm/lib/Target/AVR/AVRISelLowering.cpp b/llvm/lib/Target/AVR/AVRISelLowering.cpp
index b6ba5f2..f159bee 100644
--- a/llvm/lib/Target/AVR/AVRISelLowering.cpp
+++ b/llvm/lib/Target/AVR/AVRISelLowering.cpp
@@ -1689,6 +1689,8 @@
   if (Constraint.size() == 1) {
     // See http://www.nongnu.org/avr-libc/user-manual/inline_asm.html
     switch (Constraint[0]) {
+    default:
+      break;
     case 'a': // Simple upper registers
     case 'b': // Base pointer registers pairs
     case 'd': // Upper register
@@ -1715,9 +1717,7 @@
     case 'O': // Integer constant (Range: 8, 16, 24)
     case 'P': // Integer constant (Range: 1)
     case 'R': // Integer constant (Range: -6 to 5)x
-      return C_Other;
-    default:
-      break;
+      return C_Immediate;
     }
   }