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/AMDGPU/R600ISelLowering.cpp b/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp
index ad3f481..481a6ac 100644
--- a/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp
@@ -586,9 +586,10 @@
       Results.push_back(lowerFP_TO_UINT(N->getOperand(0), DAG));
       return;
     }
-    // Fall-through. Since we don't care about out of bounds values
-    // we can use FP_TO_SINT for uints too. The DAGLegalizer code for uint
-    // considers some extra cases which are not necessary here.
+    // Since we don't care about out of bounds values we can use FP_TO_SINT for
+    // uints too. The DAGLegalizer code for uint considers some extra cases
+    // which are not necessary here.
+    LLVM_FALLTHROUGH;
   case ISD::FP_TO_SINT: {
     if (N->getValueType(0) == MVT::i1) {
       Results.push_back(lowerFP_TO_SINT(N->getOperand(0), DAG));