Fix llvm-extract's "writing bitcode to a terminal" warning, which wasn't
working. To support this, add an is_displayed() function to raw_ostream,
and generalize Process::StandardOutIsDisplayed and friends in order to
support it.

Also, call RemoveFileOnSignal before creating a file instead of after, so
that the file isn't left behind if the program is interrupted between when
the file is created and RemoveFileOnSignal is called.

While here, add a -S to llvm-extract and port it to IRReader so that it
supports assembly input.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@81568 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/llvm-dis/llvm-dis.cpp b/tools/llvm-dis/llvm-dis.cpp
index 89073c0..43bde53 100644
--- a/tools/llvm-dis/llvm-dis.cpp
+++ b/tools/llvm-dis/llvm-dis.cpp
@@ -89,7 +89,12 @@
         OutputFilename = IFN+".ll";
     }
   }
-  
+
+  // Make sure that the Out file gets unlinked from the disk if we get a
+  // SIGINT.
+  if (OutputFilename != "-")
+    sys::RemoveFileOnSignal(sys::Path(OutputFilename));
+
   std::string ErrorInfo;
   std::auto_ptr<raw_fd_ostream> 
   Out(new raw_fd_ostream(OutputFilename.c_str(), ErrorInfo,
@@ -99,11 +104,6 @@
     return 1;
   }
 
-  // Make sure that the Out file gets unlinked from the disk if we get a
-  // SIGINT.
-  if (OutputFilename != "-")
-    sys::RemoveFileOnSignal(sys::Path(OutputFilename));
-
   // All that llvm-dis does is write the assembly to a file.
   if (!DontPrint) {
     PassManager Passes;