Summary:
ELF linkers generate __start_<secname> and __stop_<secname> symbols
when there is a value in a section <secname> where the name is a valid
C identifier. If dead stripping determines that the values declared
in section <secname> are dead, and we then internalize (and delete)
such a symbol, programs that reference the corresponding start and end
section symbols will get undefined reference linking errors.
To fix this, add the section name to the IRSymtab entry when a symbol is
defined in a specific section. Then use this in the gold-plugin to mark
the symbol as external and visible from outside the summary when the
section name is a valid C identifier.
Reviewers: pcc
Subscribers: mehdi_amini, inglorion, eraman, llvm-commits
Differential Revision: https://reviews.llvm.org/D35639
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@309009 91177308-0d34-0410-b5e6-96231b3b80d8
I did this a long time ago with a janky python script, but now
clang-format has built-in support for this. I fed clang-format every
line with a #include and let it re-sort things according to the precise
LLVM rules for include ordering baked into clang-format these days.
I've reverted a number of files where the results of sorting includes
isn't healthy. Either places where we have legacy code relying on
particular include ordering (where possible, I'll fix these separately)
or where we have particular formatting around #include lines that
I didn't want to disturb in this patch.
This patch is *entirely* mechanical. If you get merge conflicts or
anything, just ignore the changes in this patch and run clang-format
over your #include lines in the files.
Sorry for any noise here, but it is important to keep these things
stable. I was seeing an increasing number of patches with irrelevant
re-ordering of #include lines because clang-format was used. This patch
at least isolates that churn, makes it easy to skip when resolving
conflicts, and gets us to a clean baseline (again).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304787 91177308-0d34-0410-b5e6-96231b3b80d8
Marking them as used causes them to be considered visible outside of LTO. This
prevents the symbols from being internalized or discarded, either by GlobalDCE
or by summary-based dead stripping in ThinLTO.
This change makes it unnecessary to add these symbols to llvm.compiler.used
in the backend, as the symbols are kept alive by virtue of being external,
so remove the backend code that handles that.
Fixes PR32798.
Differential Revision: https://reviews.llvm.org/D32544
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301438 91177308-0d34-0410-b5e6-96231b3b80d8
Instead of storing an UncommonIndex on the Symbol, use a flag bit to store
whether the Symbol has an Uncommon. This shrinks Chromium's .bc files (after
D32061) by about 1%.
Differential Revision: https://reviews.llvm.org/D32070
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300514 91177308-0d34-0410-b5e6-96231b3b80d8
Start using it in LLD to avoid needing to read bitcode again just to get the
target triple, and in llvm-lto2 to avoid printing symbol table information
that is inappropriate for the target.
Differential Revision: https://reviews.llvm.org/D32038
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300300 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
The linker needs to be able to determine whether a symbol is text or data to
handle the case of a common being overridden by a strong definition in an
archive. If the archive contains a text member of the same name as the common,
that function is discarded. However, if the archive contains a data member of
the same name, that strong definition overrides the common. This is a behavior
of ld.bfd, which the Qualcomm linker also supports in LTO.
Here's a test case to illustrate:
####
cat > 1.c << \!
int blah;
!
cat > 2.c << \!
int blah() {
return 0;
}
!
cat > 3.c << \!
int blah = 20;
!
clang -c 1.c
clang -c 2.c
clang -c 3.c
ar cr lib.a 2.o 3.o
ld 1.o lib.a -t
####
The correct output is:
1.o
(lib.a)3.o
Thanks to Shankar Easwaran and Hemant Kulkarni for the test case!
Reviewers: mehdi_amini, rafael, pcc, davide
Reviewed By: pcc
Subscribers: davide, llvm-commits, inglorion
Differential Revision: https://reviews.llvm.org/D31901
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300205 91177308-0d34-0410-b5e6-96231b3b80d8
Introduce symbol table data structures that can be potentially written to
disk, have the LTO library build those data structures using temporarily
constructed modules and redirect the LTO library implementation to go through
those data structures. This allows us to remove the LLVMContext and Modules
owned by InputFile.
With this change I measured a peak memory consumption decrease from 5.4GB to
2.8GB in a no-op incremental ThinLTO link of Chromium on Linux. The impact on
memory consumption is larger in COFF linkers where we are currently forced
to materialize all metadata in order to read linker options. Peak memory
consumption linking a large piece of Chromium for Windows with full LTO and
debug info decreases from >64GB (OOM) to 15GB.
Part of PR27551.
Differential Revision: https://reviews.llvm.org/D31364
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@299168 91177308-0d34-0410-b5e6-96231b3b80d8
