COFF lacks a feature that other object file formats support: mergeable
sections.
To work around this, MSVC sticks constant pool entries in special COMDAT
sections so that each constant is in it's own section. This permits
unused constants to be dropped and it also allows duplicate constants in
different translation units to get merged together.
This fixes PR20262.
Differential Revision: http://reviews.llvm.org/D4482
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This new IR facility allows us to represent the object-file semantic of
a COMDAT group.
COMDATs allow us to tie together sections and make the inclusion of one
dependent on another. This is required to implement features like MS
ABI VFTables and optimizing away certain kinds of initialization in C++.
This functionality is only representable in COFF and ELF, Mach-O has no
similar mechanism.
Differential Revision: http://reviews.llvm.org/D4178
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* Section association cannot use just the section name as many
sections can have the same name. With this patch, the comdat symbol in
an assoc section is interpreted to mean a symbol in the associated
section and the mapping is discovered from it.
* Comdat symbols were not being set correctly. Instead we were getting
whatever was output first for that section.
A consequence is that associative sections now must use .section to
set the association. Using .linkonce would not work since it is not
possible to change a sections comdat symbol (it is used to decide if
we should create a new section or reuse an existing one).
This includes r210298, which was reverted because it was asserting
on an associated section having the same comdat as the associated
section.
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For MIPS, we have to encode the personality routine with
an indirect pointer to absptr; otherwise, some link warning
warning will be raised, and the program might crash in some
early MIPS Android device.
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This allows us to put dynamic initializers for weak data into the same
comdat group as the data being initialized. This is necessary for MSVC
ABI compatibility. Once we have comdats for guard variables, we can use
the combination to help GlobalOpt fire more often for weak data with
guarded initialization on other platforms.
Reviewers: nlewycky
Differential Revision: http://reviews.llvm.org/D3499
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Summary:
Local common symbols were properly inserted into the .bss section.
However, putting external common symbols in the .bss section would give
them a strong definition.
Instead, encode them as undefined, external symbols who's symbol value
is equivalent to their size.
Reviewers: Bigcheese, rafael, rnk
CC: llvm-commits
Differential Revision: http://reviews.llvm.org/D3324
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This is a pretty straight forward translation for COFF, we just need to
stick the data in a COMDAT section marked as
IMAGE_COMDAT_SELECT_NODUPLICATES.
N.B. We must be careful to avoid sticking entities with private linkage
in COMDAT groups. COFF is pretty hostile to the renaming of entities so
we must be careful to disallow GlobalVariables with unstable names.
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This is a pretty straight forward translation for COFF, we just need to
stick the function in a COMDAT section marked as
IMAGE_COMDAT_SELECT_NODUPLICATES.
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Summary:
llvm/MC/MCSectionMachO.h and llvm/Support/MachO.h both had the same
definitions for the section flags. Instead, grab the definitions out of
support.
No functionality change.
Reviewers: grosbach, Bigcheese, rafael
Reviewed By: rafael
CC: llvm-commits
Differential Revision: http://llvm-reviews.chandlerc.com/D2998
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TargetLoweringBase is implemented in CodeGen, so before this patch we had
a dependency fom Target to CodeGen. This would show up as a link failure of
llvm-stress when building with -DBUILD_SHARED_LIBS=ON.
This fixes pr18900.
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r201608 made llvm corretly handle private globals with MachO. r201622 fixed
a bug in it and r201624 and r201625 were changes for using private linkage,
assuming that llvm would do the right thing.
They all got reverted because r201608 introduced a crash in LTO. This patch
includes a fix for that. The issue was that TargetLoweringObjectFile now has
to be initialized before we can mangle names of private globals. This is
trivially true during the normal codegen pipeline (the asm printer does it),
but LTO has to do it manually.
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When outputting an object we check its section to find its name, but when
looking for the section with -ffunction-section we look for the symbol name.
Break the loop by requesting a name with the private prefix when constructing
the section name. This matches the behavior before r201608.
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The IR
@foo = private constant i32 42
is valid, but before this patch we would produce an invalid MachO from it. It
was invalid because it would use an L label in a section where the liker needs
the labels in order to atomize it.
One way of fixing it would be to just reject this IR in the backend, but that
would not be very front end friendly.
What this patch does is use an 'l' prefix in sections that we know the linker
requires symbols for atomizing them. This allows frontends to just use
private and not worry about which sections they go to or how the linker handles
them.
One small issue with this strategy is that now a symbol name depends on the
section, which is not available before codegen. This is not a problem in
practice. The reason is that it only happens with private linkage, which will
be ignored by the non codegen users (llvm-nm and llvm-ar).
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These methods normally call each other and it is really annoying if the
arguments are in different order. The more common rule was that the arguments
specific to call are first (GV, Encoding, Suffix) and the auxiliary objects
(Mang, TM) come after. This patch changes the exceptions.
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It is never null and it is not used in casts, so there is no reason to use a
pointer. This matches how we pass TM.
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code to see if we're emitting a function into a non-default
text section. This is still a less-than-ideal solution, but more
contained than r199871 to determine whether or not we're emitting
code into an array of comdat sections.
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e.g. linkonce, to TargetMachine and set it when we've done so
for ELF targets currently. This involved making TargetMachine
non-const in a TLOF use and propagating that change around - I'm
open to other ideas.
This will be used in a future commit to handle emitting debug
information with ranges.
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We currently error in clang with:
"error: thread-local storage is unsupported for the current target", but we
can start to get the llvm level ready.
When compiling
template<typename T>
struct foo {
static __declspec(thread) int bar;
};
template<typename T>
__declspec(therad) int foo<T>::bar;
template struct foo<int>;
msvc produces
SECTION HEADER #3
.tls$ name
0 physical address
0 virtual address
4 size of raw data
12F file pointer to raw data (0000012F to 00000132)
0 file pointer to relocation table
0 file pointer to line numbers
0 number of relocations
0 number of line numbers
C0301040 flags
Initialized Data
COMDAT; sym= "public: static int foo<int>::bar" (?bar@?$foo@H@@2HA)
4 byte align
Read Write
gcc produces a ".data$__emutls_v.<symbol>" for the testcase with
__declspec(thread) replaced with thread_local.
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With this patch we use simple names for COMDAT sections (like .text or .bss).
This matches the MSVC behavior.
When merging it is the COMDAT symbol that is used to decide if two sections
should be merged, so there is no point in building a fancy name.
This survived a bootstrap on mingw32.
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This is the first step to fix pr17918.
It extends the .section directive a bit, inspired by what the ELF one looks
like. The problem with using linkonce is that given
.section foo
.linkonce....
.section foo
.linkonce
we would already have switched sections when getting to .linkonce. The cleanest
solution seems to be to add the comdat information in the .section itself.
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Summary:
We need to do two things:
- Initialize BSSSection in MCObjectFileInfo::InitCOFFMCObjectFileInfo
- Teach TargetLoweringObjectFileCOFF::SelectSectionForGlobal what to do
with it
This fixes PR16861.
Reviewers: rnk
Reviewed By: rnk
CC: llvm-commits
Differential Revision: http://llvm-reviews.chandlerc.com/D1361
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This reverts commit r77814.
We were sticking global constants in the .data section instead of in the
.rdata section when emitting for COFF.
This fixes PR16831.
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Original commit message:
Stop emitting weak symbols into the "coal" sections.
The Mach-O linker has been able to support the weak-def bit on any symbol for
quite a while now. The compiler however continued to place these symbols into a
"coal" section, which required the linker to map them back to the base section
name.
Replace the sections like this:
__TEXT/__textcoal_nt instead use __TEXT/__text
__TEXT/__const_coal instead use __TEXT/__const
__DATA/__datacoal_nt instead use __DATA/__data
<rdar://problem/14265330>
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32-bit symbols have "_" as global prefix, but when forming the name of
COMDAT sections this prefix is ignored. The current behavior assumes that
this prefix is always present which is not the case for 64-bit and names
are truncated.
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This patch broke `make check-asan` on Mac, causing ld warnings like the following one:
ld: warning: direct access in __GLOBAL__I_a to global weak symbol
___asan_mapping_scale means the weak symbol cannot be overridden at
runtime. This was likely caused by different translation units being
compiled with different visibility settings.
The resulting test binaries crashed with incorrect ASan warnings.
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The Mach-O linker has been able to support the weak-def bit on any symbol for
quite a while now. The compiler however continued to place these symbols into a
"coal" section, which required the linker to map them back to the base section
name.
Replace the sections like this:
__TEXT/__textcoal_nt instead use __TEXT/__text
__TEXT/__const_coal instead use __TEXT/__const
__DATA/__datacoal_nt instead use __DATA/__data
<rdar://problem/14265330>
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Restrict the current TLS support to X86 ELF for now. Test that we don't
produce it on PPC & we can flesh that test case out with the right thing
once someone implements it.
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Based on GCC's output for TLS variables (OP_constNu, x@dtpoff,
OP_lo_user), this implements debug info support for TLS in ELF. Verified
that this output is correct/sufficient on Linux (using gold - if you're
using binutils-ld, you'll need something with the fix for
http://sourceware.org/bugzilla/show_bug.cgi?id=15685 in it).
Support on non-ELF is sort of "arbitrary" at the moment - if Apple folks
want to discuss (or just go ahead & implement) how this should work in
MachO, etc, I'm open.
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TLVs probably won't be as common as the other types of variables. Check for them
last before defaulting to "DATA".
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The linker sorts the .tls$<xyz> sections by name, and we need
to make sure any extra sections we produce (e.g. for weak globals)
always end up between .tls$AAA and .tls$ZZZ, even if the name
starts with e.g. an underscore.
Patch by David Nadlinger!
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into their new header subdirectory: include/llvm/IR. This matches the
directory structure of lib, and begins to correct a long standing point
of file layout clutter in LLVM.
There are still more header files to move here, but I wanted to handle
them in separate commits to make tracking what files make sense at each
layer easier.
The only really questionable files here are the target intrinsic
tablegen files. But that's a battle I'd rather not fight today.
I've updated both CMake and Makefile build systems (I think, and my
tests think, but I may have missed something).
I've also re-sorted the includes throughout the project. I'll be
committing updates to Clang, DragonEgg, and Polly momentarily.
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Sooooo many of these had incorrect or strange main module includes.
I have manually inspected all of these, and fixed the main module
include to be the nearest plausible thing I could find. If you own or
care about any of these source files, I encourage you to take some time
and check that these edits were sensible. I can't have broken anything
(I strictly added headers, and reordered them, never removed), but they
may not be the headers you'd really like to identify as containing the
API being implemented.
Many forward declarations and missing includes were added to a header
files to allow them to parse cleanly when included first. The main
module rule does in fact have its merits. =]
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