For a target symbol defined in the same section, currently we don't emit
a relocation if VariantKind is VK_None (with few exceptions like RISC-V
relaxation), while GNU as emits one. This causes program behavior
differences with and without -ffunction-sections, and can break intended
symbol interposition in a -shared link.
```
.globl foo
foo:
call foo # no relocation. On other targets, may be written as b foo, etc
call bar # a relocation if bar is in another section (e.g. -ffunction-sections)
call foo@plt # a relocation
```
Unify these cases by always emitting a relocation. If we ever want to
optimize `call foo` in -shared links, we should emit a STB_LOCAL alias
and call via the alias.
ARM/thumb2-beq-fixup.s: we now emit a relocation to global_thumb_fn as GNU as does.
X86/Inputs/align-branch-64-2.s: we now emit R_X86_64_PLT32 to foo as GNU does.
ELF/relax.s: rewrite the test as target-in-same-section.s .
We omitted relocations to `global` and now emit R_X86_64_PLT32.
Note, GNU as does not emit a relocation for `jmp global` (maybe its own
bug). Our new behavior is compatible except `jmp global`.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D72197
Recommit r373168, which was reverted by r373242. This actually exposed a
boringssl bug which has been fixed for more than one month.
For the following two cases, we currently suppress the symbols. This
patch emits them (compatible with GNU as).
* `test2_a = undef`: if `undef` is otherwise unused.
* `.hidden hidden`: if `hidden` is unused. This is the main point of the
patch, because omitting the symbol would cause a linker semantic
difference.
It causes a behavior change that is not compatible with GNU as:
.weakref foo1, bar1
When neither foo1 nor bar1 is used, we now emit bar1, which is arguably
more consistent.
Another change is that we will emit .TOC. for .TOC.@tocbase . For this
directive, suppressing .TOC. can be seen as a size optimization, but we
choose to drop it for simplicity and consistency.
For the following two cases, we currently suppress the symbols. This
patch emits them (compatible with GNU as).
* `test2_a = undef`: if `undef` is otherwise unused.
* `.hidden hidden`: if `hidden` is unused. This is the main point of the
patch, because omitting the symbol would cause a linker semantic
difference.
It causes a behavior change that is not compatible with GNU as:
.weakref foo1, bar1
When neither foo1 nor bar1 is used, we now emit bar1, which is arguably
more consistent.
Another change is that we will emit .TOC. for .TOC.@tocbase . For this
directive, suppressing .TOC. can be seen as a size optimization, but we
choose to drop it for simplicity and consistency.
llvm-svn: 373168
Summary:
This is patch is part of a series to introduce an Alignment type.
See this thread for context: http://lists.llvm.org/pipermail/llvm-dev/2019-July/133851.html
See this patch for the introduction of the type: https://reviews.llvm.org/D64790
Reviewers: courbet, JDevlieghere, alexshap, rupprecht, jhenderson
Subscribers: sdardis, nemanjai, hiraditya, kbarton, jakehehrlich, jrtc27, MaskRay, atanasyan, jsji, seiya, cfe-commits, llvm-commits
Tags: #clang, #llvm
Differential Revision: https://reviews.llvm.org/D67499
llvm-svn: 371742
```
.type foo,@gnu_indirect_function
.set foo,foo_resolver
.set foo2,foo
.set foo3,foo2
```
The types of foo2 and foo3 should be STT_GNU_IFUNC, but we currently
resolve them to the type of foo_resolver. This patch fixes it.
Differential Revision: https://reviews.llvm.org/D67206
Patch by Senran Zhang
llvm-svn: 371312
Replace
- error: No relocation available to represent this relative expression
with
+ error: symbol 'undef' can not be undefined in a subtraction expression
or
+ error: Cannot represent a difference across sections
Keep !IsPcRel as an assertion after the two diagnostic checks are done.
llvm-svn: 369239
GNU as keeps the original symbol in the symbol table for defined @ and
@@, but suppresses it in other cases (@@@ or undefined). The original
symbol is usually undesired:
In a shared object, the original symbol can be localized with a version
script, but it is hard to remove/localize in an archive:
1) a post-processing step removes the undesired original symbol
2) consumers (executable) of the archive are built with the
version script
Moreover, it can cause linker issues like binutils PR/18703 if the
original symbol name and the base name of the versioned symbol is the
same (both ld.bfd and gold have some code to work around defined @ and
@@). In lld, if it sees f and f@v1:
--version-script =(printf 'v1 {};') => f and f@v1
--version-script =(printf 'v1 { f; };') => f@v1 and f@@v1
It can be argued that @@@ added on 2000-11-13 corrected the @ and @@ mistake.
This patch catches some more multiple version errors (defined @ and @@),
and consistently suppress the original symbol. This addresses all the
problems listed above.
If the user wants other aliases to the versioned symbol, they can copy
the original symbol to other symbol names with .set directive, e.g.
.symver f, f@v1 # emit f@v1 but not f into .symtab
.set f_impl, f # emit f_impl into .symtab
llvm-svn: 369233
Now that we've moved to C++14, we no longer need the llvm::make_unique
implementation from STLExtras.h. This patch is a mechanical replacement
of (hopefully) all the llvm::make_unique instances across the monorepo.
llvm-svn: 369013
This reverts commit r366686 as it appears to be causing buildbot
failures on sanitizer-x86_64-linux-android and sanitizer-x86_64-linux.
llvm-svn: 366708
This patch was not the reason of the buildbot failure.
Deleted code was introduced as a work around for a bug in the gold linker
(http://sourceware.org/PR16794). Test case that was given as a reason for
this part of code, the one on previous link, now works for the gold.
This condition is too strict and when a code is compiled with debug info
it forces generation of numerous relocations with symbol for architectures
that do not have relocation addend.
Reviewers: arsenm, espindola
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D64327
llvm-svn: 366686
Deleted code was introduced as a work around for a bug in the gold linker
(http://sourceware.org/PR16794). Test case that was given as a reason for
this part of code, the one on previous link, now works for the gold.
This condition is too strict and when a code is compiled with debug info
it forces generation of numerous relocations with symbol for architectures
that do not have relocation addend.
Reviewers: arsenm, espindola
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D64327
llvm-svn: 365618
Summary:
The directive defines a symbol as an group/local memory (LDS) symbol.
LDS symbols behave similar to common symbols for the purposes of ELF,
using the processor-specific SHN_AMDGPU_LDS as section index.
It is the linker and/or runtime loader's job to "instantiate" LDS symbols
and resolve relocations that reference them.
It is not possible to initialize LDS memory (not even zero-initialize
as for .bss).
We want to be able to link together objects -- starting with relocatable
objects, but possible expanding to shared objects in the future -- that
access LDS memory in a flexible way.
LDS memory is in an address space that is entirely separate from the
address space that contains the program image (code and normal data),
so having program segments for it doesn't really make sense.
Furthermore, we want to be able to compile multiple kernels in a
compilation unit which have disjoint use of LDS memory. In that case,
we may want to place LDS symbols differently for different kernels
to save memory (LDS memory is very limited and physically private to
each kernel invocation), so we can't simply place LDS symbols in a
.lds section.
Hence this solution where LDS symbols always stay undefined.
Change-Id: I08cbc37a7c0c32f53f7b6123aa0afc91dbc1748f
Reviewers: arsenm, rampitec, t-tye, b-sumner, jsjodin
Subscribers: kzhuravl, jvesely, wdng, yaxunl, dstuttard, tpr, rupprecht, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D61493
llvm-svn: 364296
We should keep the symbol type (STT_GNU_IFUNC) for a local ifunc because
it may result in an IRELATIVE reloc that the dynamic loader will use to
resolve the address at startup time.
There is another problem that is not fixed by this patch: a PC relative
relocation should also create a relocation with the ifunc symbol.
llvm-svn: 362767
On PowerPC64 ELFv2 ABI, the top 3 bits of st_other encode the local
entry offset. A versioned symbol alias created by .symver should copy
the bits from the source symbol.
This partly fixes PR41048. A full fix needs tracking of .set assignments
and updating st_other fields when finish() is called, see D56586.
Patch by Alfredo Dal'Ava Júnior
Differential Revision: https://reviews.llvm.org/D59436
llvm-svn: 360442
About the compressed sections spec says:
(https://docs.oracle.com/cd/E37838_01/html/E36783/section_compression.html)
sh_addralign fields of the section header for a compressed section
reflect the requirements of the compressed section.
Currently, llvm-mc always puts uncompressed section alignment to sh_addralign.
It is not correct. zlib styled section contains an Elfxx_Chdr header,
so we should either use 4 or 8 values depending on the target
(Uncompressed section alignment is stored in ch_addralign field of the compression header).
GNU assembler version 2.31.1 also has this issue,
but in 2.32.51 it was already fixed. This is how it was found
during debugging of the https://bugs.llvm.org/show_bug.cgi?id=40482
actually.
Differential revision: https://reviews.llvm.org/D60965
llvm-svn: 358960
This special section is named .symtab_shndx, according to gABI Chapter 4
Sections, and the name is used by some other tools. Though the section
type SHT_SYMTAB_SHNDX is what really matters, let's fix the typo
introduced in rL204769 :)
llvm-svn: 358247
We stil don't have a source location, which is pretty lame, but at least
we won't tell the user to file a clang bug report anymore.
Fixes PR40712
llvm-svn: 353907
to reflect the new license.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351636
SHF_ARM_PURECODE flag when being built with the -mexecute-only flag.
All code sections of an ELF must have the flag set for the final .text
section to be execute-only, otherwise the flag gets removed.
A HasData flag is added to MCSection to aid in the determination that
the section is empty. A virtual setTargetSectionFlags is added to
MCELFObjectTargetWriter to allow subclasses to set target specific
section flags to be added to sections which we then use in the ARM
backend to set SHF_ARM_PURECODE.
Patch by Ivan Lozano!
Reviewed By: echristo
Differential Revision: https://reviews.llvm.org/D48792
llvm-svn: 341593
This matches our behaviour for regular (i.e. relocated) references to
private symbols and therefore avoids needing to unnecessarily write
address-significant .L symbols to the object file's symbol table,
which can interfere with stack traces.
Fixes check-cfi after r339050.
llvm-svn: 339066
Object FIle Representation
At codegen time this is emitted into the ELF file a pair of symbol indices and a weight. In assembly it looks like:
.cg_profile a, b, 32
.cg_profile freq, a, 11
.cg_profile freq, b, 20
When writing an ELF file these are put into a SHT_LLVM_CALL_GRAPH_PROFILE (0x6fff4c02) section as (uint32_t, uint32_t, uint64_t) tuples as (from symbol index, to symbol index, weight).
Differential Revision: https://reviews.llvm.org/D44965
llvm-svn: 333823
This class will be used to create regular, non-split ELF files.
Part of PR37466.
Differential Revision: https://reviews.llvm.org/D47049
llvm-svn: 332870
Also clean up a couple of hacks where we were writing the section
contents to another stream by setting the object writer's stream,
writing and setting it back.
Part of PR37466.
Differential Revision: https://reviews.llvm.org/D47038
llvm-svn: 332858
Provide some free functions to reduce verbosity of endian-writing
a single value, and replace the endianness template parameter with
a field.
Part of PR37466.
Differential Revision: https://reviews.llvm.org/D47032
llvm-svn: 332757
Summary:
Only allow a single unique .symver alias per symbol. This matches the
behavior of gas. I noticed that we ignored multiple mismatched symver
directives looking at https://reviews.llvm.org/D45798
Reviewers: pcc, tejohnson, espindola
Reviewed By: pcc
Subscribers: emaste, arichardson, llvm-commits, kcc
Differential Revision: https://reviews.llvm.org/D45845
llvm-svn: 331078
With this we only create an alias for @@@ once we know if it should
use @ or @@. This avoids last minutes renames and hacks to handle MS
names.
This only handles the ELF writer. LTO still has issues with @@@
aliases.
llvm-svn: 327160
functions.
This makes the ownership of the resulting MCObjectWriter clear, and allows us
to remove one instance of MCObjectStreamer's bizarre "holding ownership via
someone else's reference" trick.
llvm-svn: 315327
ELFObjectWriter's constructor.
Fixes the same ownership issue for ELF that r315245 did for MachO:
ELFObjectWriter takes ownership of its MCELFObjectTargetWriter, so we want to
pass this through to the constructor via a unique_ptr, rather than a raw ptr.
llvm-svn: 315254
In case of using a "nested" relocation expressions like this
`%hi(%neg(%gp_rel()))`, N32 ABI requires generation of three consecutive
relocations. That differs from the N64 ABI case where all relocations
are packed into the single relocation record.
llvm-svn: 313879
Now we pass the 'Is64_' flag to the MCELFObjectTargetWriter ctor iif
when we make deal with N64 ABI. So it is redundant to pass additional
'IsN64' flag.
llvm-svn: 313878
This is a preparatory change to expose the debug compression style to
clang. It requires exposing the enumeration and passing the actual
value through to the backend from the frontend in actual value form
rather than a boolean that selects the GNU style of debug info
compression.
Minor tweak to the ELF Object Writer to use a variable for re-used
values. Add an assertion that debug information format is one of the
two currently known types if debug information is being compressed.
llvm-svn: 305038
This creates a new library called BinaryFormat that has all of
the headers from llvm/Support containing structure and layout
definitions for various types of binary formats like dwarf, coff,
elf, etc as well as the code for identifying a file from its
magic.
Differential Revision: https://reviews.llvm.org/D33843
llvm-svn: 304864
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).
llvm-svn: 304787
Make MCSectionELF::AssociatedSection be a link to a symbol, because
that's how it works in the assembly, and use it in the asm printer.
llvm-svn: 297769
On ELF every section can have a corresponding section symbol. When in
an assembly file we have
.quad .text
the '.text' refers to that symbol.
The way we used to handle them is to leave .text an undefined symbol
until the very end when the object writer would map them to the
actual section symbol.
The problem with that is that anything before the end would see an
undefined symbol. This could result in bad diagnostics
(test/MC/AArch64/label-arithmetic-diags-elf.s), or incorrect results
when using the asm streamer (est/MC/Mips/expansion-jal-sym-pic.s).
Fixing this will also allow using the section symbol earlier for
setting sh_link of SHF_METADATA sections.
This patch includes a few hacks to avoid changing our behaviour when
handling conflicts between section symbols and other symbols. I
reported pr31850 to track that.
llvm-svn: 293936
No any changes, will follow up with D28807 commit containing APLi change for clang
to fix build issues happened.
Original commit message:
[Support/Compression] - Change zlib API to return Error instead of custom status.
Previously API returned custom enum values.
Patch changes it to return Error with string description.
That should help users to report errors in universal way.
Differential revision: https://reviews.llvm.org/D28684
llvm-svn: 292226
Previously API returned custom enum values.
Patch changes it to return Error with string description.
That should help users to report errors in universal way.
Differential revision: https://reviews.llvm.org/D28684
llvm-svn: 292214
We would attempt to access the symbol section without ensuring that the symbol
was not absolute. When the assembler referenced relocation is not evaluated to
the absolute, but when we record the relocation, we would query the section.
Because the symbol is absolute, it does not have a section associated with it,
triggering an assertion. Just be more careful about the access of the section.
Addresses PR31064!
llvm-svn: 287619
Fix: updated clang code which was not updated by mistake.
Original commit message:
[llvm-mc] - Teach llvm-mc to generate zlib styled compression sections.
This patch is strongly based on previously reverted D20331.
(because of gnuutils < 2.26 does not support compressed debug sections in non zlib-gnu style)
Difference that this patch supports both zlib and zlib-gnu styles.
-compress-debug-sections option now supports next values:
-compress-debug-sections=zlib-gnu
-compress-debug-sections=zlib
-compress-debug-sections=none
Previously specifying -compress-debug-sections enabled zlib-gnu compression,
so anyone can put "-compress-debug-sections=zlib-gnu" to restore the behavior
that was before this patch for case when compression was enabled.
Differential revision: http://reviews.llvm.org/D20676
llvm-svn: 270987
It broke buildbot:
http://lab.llvm.org:8011/builders/llvm-clang-lld-x86_64-scei-ps4-ubuntu-fast/builds/13585/steps/build/logs/stdio
Initial commit message:
[llvm-mc] - Teach llvm-mc to generate zlib styled compression sections.
This patch is strongly based on previously reverted D20331.
(because of gnuutils < 2.26 does not support compressed debug sections in non zlib-gnu style)
Difference that this patch supports both zlib and zlib-gnu styles.
-compress-debug-sections option now supports next values:
-compress-debug-sections=zlib-gnu
-compress-debug-sections=zlib
-compress-debug-sections=none
Previously specifying -compress-debug-sections enabled zlib-gnu compression,
so anyone can put "-compress-debug-sections=zlib-gnu" to restore the behavior
that was before this patch for case when compression was enabled.
Differential revision: http://reviews.llvm.org/D20676
llvm-svn: 270978
This patch is strongly based on previously reverted D20331.
(because of gnuutils < 2.26 does not support compressed debug sections in non zlib-gnu style)
Difference that this patch supports both zlib and zlib-gnu styles.
-compress-debug-sections option now supports next values:
-compress-debug-sections=zlib-gnu
-compress-debug-sections=zlib
-compress-debug-sections=none
Previously specifying -compress-debug-sections enabled zlib-gnu compression,
so anyone can put "-compress-debug-sections=zlib-gnu" to restore the behavior
that was before this patch for case when compression was enabled.
Differential revision: http://reviews.llvm.org/D20676
llvm-svn: 270977
Now, after landing r270560, r270557, r270320 it is a proper time.
Original commit message:
[llvm-mc] - Teach llvm-mc to generate compressed debug sections in zlib style.
Before this patch llvm-mc generated zlib-gnu styled sections.
That means no SHF_COMPRESSED flag was set, magic 'zlib' signature
was used in combination with full size field. Sections were renamed to "*.z*".
This patch reimplements the compression style to zlib one as zlib-gnu looks
to be depricated everywhere.
Differential revision: http://reviews.llvm.org/D20331
llvm-svn: 270569
It broke buildbot:
http://lab.llvm.org:8011/builders/clang-s390x-linux/builds/4817/steps/ninja%20check%201/logs/stdio
Actually it is just because D20273 not yet commited, but these 2 were crossing with each other,
and I`ll better find the way to land them separatelly soon.
Initial commit message:
[llvm-mc] - Teach llvm-mc to generate compressed debug sections in zlib style.
Before this patch llvm-mc generated zlib-gnu styled sections.
That means no SHF_COMPRESSED flag was set, magic 'zlib' signature
was used in combination with full size field. Sections were renamed to "*.z*".
This patch reimplements the compression style to zlib one as zlib-gnu looks
to be depricated everywhere.
Differential revision: http://reviews.llvm.org/D20331
llvm-svn: 270075
Before this patch llvm-mc generated zlib-gnu styled sections.
That means no SHF_COMPRESSED flag was set, magic 'zlib' signature
was used in combination with full size field. Sections were renamed to "*.z*".
This patch reimplements the compression style to zlib one as zlib-gnu looks
to be depricated everywhere.
Differential revision: http://reviews.llvm.org/D20331
llvm-svn: 270070
Summary:
There seems to have been a misunderstanding as to the meaning of 'offset' in
the rules laid down by our ABI. The previous code believed that 'offset' meant
the offset within the section that the relocation is applied to. However, it
should have meant the offset from the symbol used in the relocation expression.
This patch adds two fields to ELFRelocationEntry and uses them to correct the
order of relocations for MIPS. These fields contain:
* The original symbol before shouldRelocateWithSymbol() is considered. This
ensures that R_MIPS_GOT16 is able to correctly distinguish between local and
external symbols, allowing us to tell whether %got() requires a matching
%lo() or not (local symbols require one, external symbols don't). It also
prevents confusing cases where the fuzzy matching rules cause things like
%hi(foo)/%lo(foo+3) and %hi(bar)/%lo(bar+1) to swap their %lo()'s.
* The original offset before shouldRelocateWithSymbol() is considered. The
existing Addend field is always zero when the object uses in place addends
(because it's already moved it to the encoding) but MIPS needs to use the
original offset to ensure that the linker correctly calculates the carry-in
bit for %hi() and %got().
IAS ensures that unmatchable %hi()/%got() relocations are placed at the end of
the table to ensure that the linker rejects the table (we're unable to report
such errors directly). The alternatives to this risk accidental matching
against inappropriate relocations which may silently compute incorrect values
due to an incorrect carry bit between the %lo() and %hi()/%got().
Reviewers: sdardis
Subscribers: dsanders, sdardis, rafael, llvm-commits
Differential Revision: http://reviews.llvm.org/D19718
llvm-svn: 268733
Summary:
This is much closer to the way MIPS relocation expressions work
(%hi(foo + 2) rather than %hi(foo) + 2) and removes the need for the
various bodges in MipsAsmParser::evaluateRelocExpr().
Removing those bodges ensures that the constant stored in MCValue is the
full 32 or 64-bit (depending on ABI) offset from the symbol. This will be used
to correct the %hi/%lo matching needed to sort the relocation table correctly.
As part of this:
* Gave MCExpr::print() the ability to omit parenthesis when emitting a
symbol reference inside a MipsMCExpr operator like %hi(X). Without this
we print things like %lo(($L1)).
* %hi(%neg(%gprel(X))) is now three MipsMCExpr's instead of one. Most of
the related special cases have been removed or moved to MipsMCExpr. We
can remove the rest as we gain support for the less common relocations
when they are not part of this specific combination.
* Renamed MipsMCExpr::VariantKind and the enum prefix ('VK_') to avoid confusion
with MCSymbolRefExpr::VariantKind and its prefix (also 'VK_').
* fixup_Mips_GOT_Local and fixup_Mips_GOT_Global were found to be identical
and merged into fixup_Mips_GOT.
* MO_GOT16 and MO_GOT turned out to be identical and have been merged into
MO_GOT.
* VK_Mips_GOT and VK_Mips_GOT16 turned out to be the same thing so they
have been merged into MEK_GOT
Reviewers: sdardis
Subscribers: dsanders, sdardis, llvm-commits
Differential Revision: http://reviews.llvm.org/D19716
llvm-svn: 268379
This is a fix for PR26941.
When there is both a section and a global definition with the same
name, the global wins.
Section symbols are not added to the symbol table; section references
are left undefined and fixed up in the object writer unless they've
been satisfied by some other definition.
llvm-svn: 264649
When a symbol S shows up in an expression in assembly there are two
possible interpretations
* The expression is referring to the value of S in this file.
* The expression is referring to the value after symbol resolution.
In the first case the assembler can reason about the value and try to
produce a relocation.
In the second case, that is only possible if the symbol cannot be
preempted.
Assemblers are not very consistent about which interpretation gets used.
This changes MC to agree with GAS in the case of an expression of the
form "Sym - WeakSym".
llvm-svn: 258329
These days relocations are created and stored in a deterministic way.
The order they are created is also suitable for the .o file, so we don't
need an explicit sort.
The last remaining exception is MIPS.
llvm-svn: 255902
Currently, if the assembler encounters an error after parsing (such as an
out-of-range fixup), it reports this as a fatal error, and so stops after the
first error. However, for most of these there is an obvious way to recover
after emitting the error, such as emitting the fixup with a value of zero. This
means that we can report on all of the errors in a file, not just the first
one. MCContext::reportError records the fact that an error was encountered, so
we won't actually emit an object file with the incorrect contents.
Differential Revision: http://reviews.llvm.org/D14717
llvm-svn: 253328
In this mode it just tries to tail merge the strings without imposing any other
format constrains. It will not, for example, add a null byte between them.
Also add support for keeping a tentative size and offset if we decide to
not optimize after all.
This will be used shortly in lld for merging SHF_STRINGS sections.
llvm-svn: 251153
This extends the work done in r233995 so that now getFragment (in addition to
getSection) also works for variable symbols.
With that the existing logic to decide if a-b can be computed works even if
a or b are variables. Given that, the expression evaluation can avoid expanding
variables as aggressively and that in turn lets the relocation code see the
original variable.
In order for this to work with the asm streamer, there is now a dummy fragment
per section. It is used to assign a section to a symbol when no other fragment
exists.
This patch is a joint work by Maxim Ostapenko andy myself.
llvm-svn: 249303
There are occasions where it is useful to consider the entirety of the
contents of a section. For example, compressed debug info needs the
entire section available before it can compress it and write it out.
The compressed debug info scenario was previously implemented by
mirroring the implementation of writeSectionData in the ELFObjectWriter.
Instead, allow the output stream to be swapped on demand. This lets
callers redirect the output stream to a more convenient location before
it hits the object file.
No functionality change is intended.
Differential Revision: http://reviews.llvm.org/D12509
llvm-svn: 246554
This causes errors like:
ld: error: blah.o: requires dynamic R_X86_64_PC32 reloc against '' which
may overflow at runtime; recompile with -fPIC
blah.cc:function f(): error: undefined reference to ''
blah.o:g(): error: undefined reference to ''
I have not yet come up with an appropriate reproduction.
llvm-svn: 240394
Now that pr23900 is fixed, we can bring it back with no changes.
Original message:
Make all temporary symbols unnamed.
What this does is make all symbols that would otherwise start with a .L
(or L on MachO) unnamed.
Some of these symbols still show up in the symbol table, but we can just
make them unnamed.
In order to make sure we produce identical results when going thought assembly,
all .L (not just the compiler produced ones), are now unnamed.
Running llc on llvm-as.opt.bc, the peak memory usage goes from 208.24MB to
205.57MB.
llvm-svn: 240302
Fangrui Song