The attribute '__declspec(noalias)' communicates that the function only
accesses memory pointed to by its pointer-typed arguments.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@242728 91177308-0d34-0410-b5e6-96231b3b80d8
Things can't both be in comdats and have common linkage, so never give things
in comdats common linkage. Common linkage is only used in .c files, and the
only thing that can trigger a comdat in c is selectany from what I can tell.
Fixes PR23243.
Also address an over-the-shoulder review comment from rnk by moving the
hasAttr<SelectAnyAttr>() in Decl.cpp around a bit. It only makes a minor
difference for selectany on global variables, so it goes well with the rest of
this patch.
http://reviews.llvm.org/D9042
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The llvm IR until recently had no support for comdats. This was a problem when
targeting C++ on ELF/COFF as just using weak linkage would cause quite a bit of
dead bits to remain on the executable (unless -ffunction-sections,
-fdata-sections and --gc-sections were used).
To fix the problem, llvm's codegen will just assume that any weak or linkonce
that is not in an explicit comdat should be output in one with the same name as
the global.
This unfortunately breaks cases like pr19848 where a weak symbol is not
xpected to be part of any comdat.
Now that we have explicit comdats in the IR, we can finally get both cases
right.
This first patch just makes clang give explicit comdats to GlobalValues where
t is allowed to.
A followup patch to llvm will then stop implicitly producing comdats.
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selectany only applies to externally visible global variables. It has
the effect of making the data weak_odr.
The MSDN docs suggest that unused definitions can only be dropped at
linktime, so Clang uses weak instead of linkonce. MSVC optimizes away
references to constant selectany data, so it must assume that there is
only one definition, hence weak_odr.
Reviewers: espindola
Differential Revision: http://llvm-reviews.chandlerc.com/D814
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This is an ongoing process. Any command line option which a back-end cares about
should be added here.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@176009 91177308-0d34-0410-b5e6-96231b3b80d8
The original r158700 caused crashes in the gcc test suite,
g++.abi/vtable3a.C among others. It also caused failures in the libc++
test suite.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@158749 91177308-0d34-0410-b5e6-96231b3b80d8
Akira Hatanaka