Prevent link warnings due to -Wframe-larger-than=

Although this is nominally a -W option, we actually handle it in the driver
exactly as an f-group flag that's translated directly to -mllvm.

That means f_Group (and unintuitively, not W_Group) has the semantics we want
to make it behave like a standard warning flag: no automatic forwarding, no
warning for link invocations and compile-only.

Silences diagnostics like:

  [691/1545] Linking CXX executable bin/llvm-diff
  clang-3.5: warning: argument unused during compilation: '-Wframe-larger-than=2048'

(Hopefully we can move towards handling these in the frontend but that'll
require some infrastructure work.)

llvm-svn: 212670

1 files changed, 4 insertions, 0 deletions

diff --git a/clang/test/Misc/backend-stack-frame-diagnostics.cpp b/clang/test/Misc/backend-stack-frame-diagnostics.cpp
index 4694299f401..1d865e7646e 100644
--- a/clang/test/Misc/backend-stack-frame-diagnostics.cpp
+++ b/clang/test/Misc/backend-stack-frame-diagnostics.cpp
@@ -6,6 +6,10 @@
 //  * The driver passes the option through to the backend.
 //  * The frontend diagnostic handler 'demangles' and resolves the correct function definition.
 
+// Test that link invocations don't emit an "argument unused during compilation" diagnostic.
+// RUN: touch %t.o
+// RUN: %clang -Werror -Wframe-larger-than=0 %t.o -###  2>&1 | not grep ' error: '
+
 // TODO: Support rich backend diagnostics for Objective-C methods.
 
 // Backend diagnostics aren't suppressed in system headers because such results