Completely re-work how the Clang driver interprets PIC and PIE options.
There were numerous issues here that were all entangled, and so I've
tried to do a general simplification of the logic.
1) The logic was mimicing actual GCC bugs, rather than "features". These
have been fixed in trunk GCC, and this fixes Clang as well. Notably,
the logic was always intended to be last-match-wins like any other
flag.
2) The logic for handling '-mdynamic-no-pic' was preposterously unclear.
It also allowed the use of this flag on non-Darwin platforms where it
has no actual meaning. Now this option is handled directly based on
tests of how llvm-gcc behaves, and it is only supported on Darwin.
3) The APIs for the Driver's ToolChains had the implementation ugliness
of dynamic-no-pic leaking through them. They also had the
implementation details of the LLVM relocation model flag names
leaking through.
4) The actual results of passing these flags was incorrect on Darwin in
many cases. For example, Darwin *always* uses PIC level 2 if it uses
in PIC level, and Darwin *always* uses PIC on 64-bit regardless of
the flags specified, including -fPIE. Darwin never compiles in PIE
mode, but it can *link* in PIE mode.
5) Also, PIC was not always being enabled even when PIE was. This isn't
a supported mode at all and may have caused some fallout in builds
with complex PIC and PIE interactions.
The result is (I hope) cleaner and clearer for readers. I've also left
comments and tests about some of the truly strage behavior that is
observed on Darwin platforms. We have no real testing of Windows
platforms and PIC, but I don't have the tools handy to figure that out.
Hopefully others can beef up our testing here.
Unfortunately, I can't test this for every platform. =/ If folks have
dependencies on these flags that aren't covered by tests, they may
break. I've audited and ensured that all the changes in behavior of the
existing tests are intentional and good. In particular I've tried to
make sure the Darwin behavior (which is more suprising than the Linux
behavior) also matches that of 'gcc' on my mac.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@168297 91177308-0d34-0410-b5e6-96231b3b80d8
7 files changed