More explicit keywords.

llvm-svn: 40589
diff --git a/llvm/lib/Target/ARM/ARMFrameInfo.h b/llvm/lib/Target/ARM/ARMFrameInfo.h
index c56640a..67ea7b6 100644
--- a/llvm/lib/Target/ARM/ARMFrameInfo.h
+++ b/llvm/lib/Target/ARM/ARMFrameInfo.h
@@ -23,7 +23,7 @@
 
 class ARMFrameInfo : public TargetFrameInfo {
 public:
-  ARMFrameInfo(const ARMSubtarget &ST)
+  explicit ARMFrameInfo(const ARMSubtarget &ST)
     : TargetFrameInfo(StackGrowsDown, ST.getStackAlignment(), 0) {
   }
 };