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.
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the second half of link-global-to-func.ll and causes some minor changes in
messages.
There are two TODOs here. First, this causes a regression in
2008-07-06-AliasWeakDest.ll, which is now failing (so I xfailed it). Anton,
I would really appreciate it if you could take a look at this. It should be
a matter of adding proper alias support to GetLinkageResult, and was probably
already a latent bug that would manifest with globals.
The second todo is to reimplement LinkAlias in the same pattern as
function and global linking. This should be pretty straight-forward for
someone who knows aliases, but isn't a requirement for correctness.
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(replacing a function with a global). This is needed when building
llvm itself with LTO on darwin, because of the EXPLICIT_SYMBOL hack
in lib/system/DynamicLibrary.cpp.
Implementation of linking the other way will need to wait for a
cleanup of LinkFunctionProtos.
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a vector with a linear search. This speeds up the linking testcase
in PR1860 from 0.965s to 0.385s on my system.
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client that cares and simplifying its control flow.
Remove the DestST argument to ResolveTypes and RecursiveResolveTypes*
which are dead now.
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function into a weak function, zap the weak function body so that the
strong one overrides it. This fixes PR2410
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function bodies. We now don't try to unify types or handling type
mismatches if when linking an internal foo to an external foo.
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the section or the visibility from one global
value to another: copyAttributesFrom. This is
particularly useful for duplicating functions:
previously this was done by explicitly copying
each attribute in turn at each place where a
new function was created out of an old one, with
the result that obscure attributes were regularly
forgotten (like the collector or the section).
Hopefully now everything is uniform and nothing
is forgotten.
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are represented as "weak", but there are subtle differences
in some cases on Darwin, so we need both. The intent
is that "common" will behave identically to "weak" unless
somebody changes their target to do something else.
No functional change as yet.
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Specifically, introduction of XXX::Create methods
for Users that have a potentially variable number of
Uses.
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start of a filename, not a filename+length. All clients can produce a
null terminated name, and the system api's require null terminated
strings anyway.
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