and extern_weak_odr. These are the same as the non-odr versions,
except that they indicate that the global will only be overridden
by an *equivalent* global. In C, a function with weak linkage can
be overridden by a function which behaves completely differently.
This means that IP passes have to skip weak functions, since any
deductions made from the function definition might be wrong, since
the definition could be replaced by something completely different
at link time. This is not allowed in C++, thanks to the ODR
(One-Definition-Rule): if a function is replaced by another at
link-time, then the new function must be the same as the original
function. If a language knows that a function or other global can
only be overridden by an equivalent global, it can give it the
weak_odr linkage type, and the optimizers will understand that it
is alright to make deductions based on the function body. The
code generators on the other hand map weak and weak_odr linkage
to the same thing.
llvm-svn: 66339
and clean recursive descent parser.
This change has a couple of ramifications:
1. The parser code is about 400 lines shorter (in what we maintain, not
including what is autogenerated).
2. The code should be significantly faster than the old code because we
don't have to work around bison's poor handling of datatypes with
ctors/dtors. This also makes the code much more resistant to memory
leaks.
3. We now get caret diagnostics from the .ll parser, woo.
4. The actual diagnostics emited from the parser are completely different
so a bunch of testcases had to be updated.
5. I now disallow "%ty = type opaque %ty = type i32". There was no good
reason to support this, it was just an accident of the old
implementation. I have no reason to think that anyone is actually using
this.
6. The syntax for sticking a global variable has changed to make it
unambiguous. I don't think anyone is depending on this since only clang
supports this and it is not solid yet, so I'm not worried about anything
breaking.
7. This gets rid of the last use of bison, and along with it the .cvs files.
I'll prune this from the makefiles as a subsequent commit.
There are a few minor cleanups that can be done after this commit (suggestions
welcome!) but this passes dejagnu testing and is ready for its time in the
limelight.
llvm-svn: 61558
Duncan Sands