Replace "fallthrough" comments with LLVM_FALLTHROUGH

This is a mechanical change of comments in switches like fallthrough,
fall-through, or fall-thru to use the LLVM_FALLTHROUGH macro instead.

llvm-svn: 278902
diff --git a/llvm/lib/Target/ARM/ARMFrameLowering.cpp b/llvm/lib/Target/ARM/ARMFrameLowering.cpp
index 0540745..cfc0faaa 100644
--- a/llvm/lib/Target/ARM/ARMFrameLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMFrameLowering.cpp
@@ -356,7 +356,7 @@
         GPRCS2Size += 4;
         break;
       }
-      // fallthrough
+      LLVM_FALLTHROUGH;
     case ARM::R0:
     case ARM::R1:
     case ARM::R2:
@@ -559,7 +559,7 @@
       case ARM::R12:
         if (STI.splitFramePushPop())
           break;
-        // fallthrough
+        LLVM_FALLTHROUGH;
       case ARM::R0:
       case ARM::R1:
       case ARM::R2:
@@ -1558,7 +1558,7 @@
       switch (Reg) {
       case ARM::LR:
         LRSpilled = true;
-        // Fallthrough
+        LLVM_FALLTHROUGH;
       case ARM::R0: case ARM::R1:
       case ARM::R2: case ARM::R3:
       case ARM::R4: case ARM::R5: