Teach Clang about PIE compilations. This is the first step of PR12380.

First, this patch cleans up the parsing of the PIC and PIE family of
options in the driver. The existing logic failed to claim arguments all
over the place resulting in kludges that marked the options as unused.
Instead actually walk all of the arguments and claim them properly.

We now treat -f{,no-}{pic,PIC,pie,PIE} as a single set, accepting the
last one on the commandline. Previously there were lots of ordering bugs
that could creep in due to the nature of the parsing. Let me know if
folks would like weird things such as "-fPIE -fno-pic" to turn on PIE,
but disable full PIC. This doesn't make any sense to me, but we could in
theory support it.

Options that seem to have intentional "trump" status (-static, -mkernel,
etc) continue to do so and are commented as such.

Next, a -pie-level flag is threaded into the frontend, rigged to
a language option, and handled preprocessor, setting up the appropriate
defines. We'll now have the correct defines when compiling with -fpie.

The one place outside of the preprocessor that was inspecting the PIC
level (as opposed to the relocation model, which is set and handled
separately, yay!) is in the GNU ObjC runtime. I changed it to exactly
preserve existing behavior. If folks want to change its behavior in the
face of PIE, they can do that in a separate patch.

Essentially the only functionality changed here is the preprocessor
defines and bug-fixes to the argument management.

Tests have been updated and extended to test all of this a bit more
thoroughly.

llvm-svn: 154291

1 files changed, 4 insertions, 0 deletions

diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index 37e89173abc..c1b9d57f09d 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -528,6 +528,10 @@ static void InitializePredefinedMacros(const TargetInfo &TI,
     Builder.defineMacro("__PIC__", Twine(PICLevel));
     Builder.defineMacro("__pic__", Twine(PICLevel));
   }
+  if (unsigned PIELevel = LangOpts.PIELevel) {
+    Builder.defineMacro("__PIE__", Twine(PIELevel));
+    Builder.defineMacro("__pie__", Twine(PIELevel));
+  }
 
   // Macros to control C99 numerics and <float.h>
   Builder.defineMacro("__FLT_EVAL_METHOD__", Twine(TI.getFloatEvalMethod()));