Introduce new linkage types linkonce_odr, weak_odr, common_odr

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.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@66339 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 6 insertions, 5 deletions

diff --git a/docs/ProgrammersManual.html b/docs/ProgrammersManual.html
index 289a569024..cf46a97e68 100644
--- a/docs/ProgrammersManual.html
+++ b/docs/ProgrammersManual.html
@@ -3322,11 +3322,12 @@ never change at runtime).</p>
     <p>Create a new global variable of the specified type. If
     <tt>isConstant</tt> is true then the global variable will be marked as
     unchanging for the program. The Linkage parameter specifies the type of
-    linkage (internal, external, weak, linkonce, appending) for the variable. If
-    the linkage is InternalLinkage, WeakLinkage, or LinkOnceLinkage,&nbsp; then
-    the resultant global variable will have internal linkage.  AppendingLinkage
-    concatenates together all instances (in different translation units) of the
-    variable into a single variable but is only applicable to arrays.  &nbsp;See
+    linkage (internal, external, weak, linkonce, appending) for the variable.
+    If the linkage is InternalLinkage, WeakAnyLinkage, WeakODRLinkage,
+    LinkOnceAnyLinkage or LinkOnceODRLinkage,&nbsp; then the resultant
+    global variable will have internal linkage.  AppendingLinkage concatenates
+    together all instances (in different translation units) of the variable
+    into a single variable but is only applicable to arrays.  &nbsp;See
     the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
     further details on linkage types. Optionally an initializer, a name, and the
     module to put the variable into may be specified for the global variable as