Commit Graph

126 Commits

Author SHA1 Message Date
Georgii Rymar 60f161eb62 [yaml2obj][obj2yaml] - Simplify format of the SHT_LLVM_ADDRSIG section.
Previously the description allowed to describe symbols with use of
`Name` and `Index` keys. This patch removes them and now it is still
possible to use either names or symbol indexes, but the code is simpler
and the format is slightly different.

Such a change will be useful for another patches, e.g:
https://reviews.llvm.org/D73788#inline-671077

Differential revision: https://reviews.llvm.org/D73888
2020-02-05 12:33:14 +03:00
Georgii Rymar bec54e464e [yaml2obj/obj2yaml] - Add support for the SHT_LLVM_CALL_GRAPH_PROFILE section.
This is a LLVM specific section that is well described here:
https://llvm.org/docs/Extensions.html#sht-llvm-call-graph-profile-section-call-graph-profile

This patch teaches yaml2obj and obj2yaml about how to work with it.

Differential revision: https://reviews.llvm.org/D73788
2020-02-04 15:13:20 +03:00
Krzysztof Parzyszek 305bf5b21d [Hexagon] Add support for Hexagon v67t microarchitecture (tiny core) 2020-01-21 11:35:10 -06:00
Krzysztof Parzyszek c12a5917d2 [Hexagon] Add support for Hexagon/HVX v67 ISA 2020-01-20 16:16:49 -06:00
Krzysztof Parzyszek ecf0766cf1 [Hexagon] Add ELF flags for Hexagon v66 to ELFYAML.cpp 2020-01-16 15:01:00 -06:00
Georgii Rymar 7570d387c2 [yaml2obj/obj2yaml] - Add support for SHT_RELR sections.
Note: this is a reland with a trivial 2 lines fix in ELFState<ELFT>::writeSectionContent.
      It adds a check similar to ones we already have for other sections to fix the case revealed
      by bots, like http://lab.llvm.org:8011/builders/llvm-clang-lld-x86_64-scei-ps4-ubuntu-fast/builds/60744.

The encoded sequence of Elf*_Relr entries in a SHT_RELR section looks
like [ AAAAAAAA BBBBBBB1 BBBBBBB1 ... AAAAAAAA BBBBBB1 ... ]
i.e. start with an address, followed by any number of bitmaps. The address
entry encodes 1 relocation. The subsequent bitmap entries encode up to 63(31)
relocations each, at subsequent offsets following the last address entry.

More information is here:
https://github.com/llvm-mirror/llvm/blob/master/lib/Object/ELF.cpp#L272

This patch adds a support for these sections.

Differential revision: https://reviews.llvm.org/D71872
2020-01-15 15:15:24 +03:00
Georgii Rymar ca6f616532 Revert "[yaml2obj/obj2yaml] - Add support for SHT_RELR sections."
This reverts commit 46d11e30ee.

It broke bots. E.g. http://lab.llvm.org:8011/builders/llvm-clang-lld-x86_64-scei-ps4-ubuntu-fast/builds/60744
2020-01-15 14:19:00 +03:00
Georgii Rymar 46d11e30ee [yaml2obj/obj2yaml] - Add support for SHT_RELR sections.
The encoded sequence of Elf*_Relr entries in a SHT_RELR section looks
like [ AAAAAAAA BBBBBBB1 BBBBBBB1 ... AAAAAAAA BBBBBB1 ... ]
i.e. start with an address, followed by any number of bitmaps. The address
entry encodes 1 relocation. The subsequent bitmap entries encode up to 63(31)
relocations each, at subsequent offsets following the last address entry.

More information is here:
https://github.com/llvm-mirror/llvm/blob/master/lib/Object/ELF.cpp#L272

This patch adds a support for these sections.

Differential revision: https://reviews.llvm.org/D71872
2020-01-15 13:54:08 +03:00
Georgii Rymar f027e1a68d [yaml2obj] - Allow using an arbitrary value for OSABI.
There was no way to set an unsupported or unknown OS ABI.
With this patch it is possible to use any numeric value.

Differential revision: https://reviews.llvm.org/D71765
2019-12-23 13:29:52 +03:00
Georgii Rymar 1f98577556 [yaml2obj] - Add support for ELFOSABI_LINUX.
ELFOSABI_LINUX is an alias for ELFOSABI_GNU.
It is not that obvious probably.

Differential revision: https://reviews.llvm.org/D71764
2019-12-23 13:25:58 +03:00
Georgii Rymar 86e652f828 [yaml2obj] - Add a way to override sh_flags section field.
Currently we have the `Flags` property that allows to
set flags for a section. The problem is that it does not
allow us to set an arbitrary value, because of bit fields
validation under the hood. An arbitrary values can be used
to test specific broken cases.

We probably do not want to relax the validation, so this
patch adds a `ShSize` property that allows to
override the `sh_size`. It is inline with others `Sh*` properties
we have already.

Differential revision: https://reviews.llvm.org/D71411
2019-12-13 11:54:37 +03:00
Peter Smith 2120612e46 [ELF] Support for PT_GNU_PROPERTY in header and tools
The PT_GNU_PROPERTY is generated by a linker to describe the
.note.gnu.property section. The Linux kernel uses this program header to
locate the .note.gnu.property section.

It is described in "The Linux gABI extension"

Include support for llvm-readelf, llvm-readobj and the yaml reader and
writers.

Differential Revision: https://reviews.llvm.org/D70959
2019-12-04 15:38:12 +00:00
Georgii Rymar 13cbcf1c1a [yaml2obj] - Add a way to describe content of the SHT_GNU_verneed section with "Content".
There is no way to set raw content for SHT_GNU_verneed section.
This patch implements it.

Differential revision: https://reviews.llvm.org/D70816
2019-11-29 10:50:00 +03:00
Georgii Rymar f69ac55d60 [yaml2obj] - Teach tool to describe SHT_GNU_verdef section with a "Content" property.
There is no way to set raw content for SHT_GNU_verdef section.
This patch implements it.

Differential revision: https://reviews.llvm.org/D70710
2019-11-26 15:35:05 +03:00
Georgii Rymar 9659464d7e [yaml2obj/obj2yaml] - Add support for SHT_LLVM_DEPENDENT_LIBRARIES sections.
This section contains strings specifying libraries to be added to the link by the linker.
The strings are encoded as standard null-terminated UTF-8 strings.

This patch adds a way to describe and dump SHT_LLVM_DEPENDENT_LIBRARIES sections.

I introduced a new YAMLFlowString type here. That used to teach obj2yaml to dump
them like:

```
Libraries: [ foo, bar ]
```

instead of the following (if StringRef would be used):

```
Libraries:
  - foo
  - bar
```

Differential revision: https://reviews.llvm.org/D70598
2019-11-25 12:57:53 +03:00
Georgii Rymar dd101539da [yaml2obj/obj2yaml] - Add support for SHT_LLVM_LINKER_OPTIONS sections.
SHT_LLVM_LINKER_OPTIONS section contains pairs of null-terminated strings.
This patch adds support for them.

Differential revision: https://reviews.llvm.org/D69895
2019-11-12 09:55:20 +03:00
Georgii Rymar 06456daa9e [yaml2obj] - Add a way to describe the custom data that is not part of an output section.
Currently there is no way to describe the data that is not a part of an output section.
It can be a data used to align sections or to fill the gaps with something,
or another kind of custom data. In this patch I suggest a way to describe it. It looks like that:

```
Sections:
  - Type:    CustomFiller
    Pattern: "CCDD"
    Size:    4
  - Name:    .bar
    Type:    SHT_PROGBITS
    Content: "FF"
```

I.e. I've added a kind of synthetic section with a synthetic type "CustomFiller".
In the code it is called a "SyntheticFiller", which is "a synthetic section which
might be used to write the custom data around regular output sections. It does
not present in the sections header table, but it might affect the output file size and
program headers produced. Think about it as about piece of data."

`SyntheticFiller` currently has a `Pattern` field and a `Size` field + an optional `Name`.
When written, `Size` of bytes in the output will be filled with a `Pattern`.
It is possible to reference a named filler it by name from the program headers description,
just like any other normal section.

Differential revision: https://reviews.llvm.org/D69709
2019-11-11 11:48:23 +03:00
georgerim a7aee6c47a [yaml2obj/obj2yaml] - Add support for SHT_GNU_HASH section.
This adds parsing and dumping support for GNU hash sections.
They are described nicely here: https://blogs.oracle.com/solaris/gnu-hash-elf-sections-v2

Differential revision: https://reviews.llvm.org/D69399
2019-10-31 12:25:37 +03:00
Georgii Rymar 5b118a0471 [yaml2obj] - Improve handling of the SHT_GROUP section.
Currently, when we do not specify "Info" field in a YAML description
for SHT_GROUP section, yaml2obj reports an error:
"error: unknown symbol referenced: '' by YAML section '.group1'"

Also, we do not link it with a symbol table by default,
though it is what we do for AddrsigSection, HashSection, RelocationSection.
(http://www.sco.com/developers/gabi/latest/ch4.sheader.html#sh_link)

The patch fixes missings mentioned.

Differential revision: https://reviews.llvm.org/D69299
2019-10-29 11:09:12 +03:00
georgerim de3cef1d5d [yaml2obj, obj2yaml] - Add support for SHT_NOTE sections.
SHT_NOTE is the section that consists of
namesz, descsz, type, name + padding, desc + padding data.
This patch teaches yaml2obj, obj2yaml to dump and parse them.

This patch implements the section how it is described here:
https://docs.oracle.com/cd/E23824_01/html/819-0690/chapter6-18048.html
Which says: "For 64–bit objects and 32–bit objects, each entry is an array of 4-byte words in
the format of the target processor"

The official specification is different
http://www.sco.com/developers/gabi/latest/ch5.pheader.html#note_section
And says: "n 64-bit objects (files with e_ident[EI_CLASS] equal to ELFCLASS64), each entry is an array
of 8-byte words in the format of the target processor. In 32-bit objects (files with e_ident[EI_CLASS]
equal to ELFCLASS32), each entry is an array of 4-byte words in the format of the target processor"

Since LLVM uses the first, 32-bit way, this patch follows it.

Differential revision: https://reviews.llvm.org/D68983
2019-10-25 13:25:56 +03:00
George Rimar c18585e32e [yaml2obj] - Add a Size tag support for SHT_LLVM_ADDRSIG sections.
It allows using "Size" with or without "Content" in YAML descriptions of
SHT_LLVM_ADDRSIG sections.

Differential revision: https://reviews.llvm.org/D68334

llvm-svn: 373610
2019-10-03 15:02:18 +00:00
George Rimar fc9104d42a Recommit r373598 "[yaml2obj/obj2yaml] - Add support for SHT_LLVM_ADDRSIG sections."
Fix: call `consumeError()` for a case missed.

Original commit message:

SHT_LLVM_ADDRSIG is described here:
https://llvm.org/docs/Extensions.html#sht-llvm-addrsig-section-address-significance-table

This patch teaches tools to dump them and to parse the YAML declarations of such sections.

Differential revision: https://reviews.llvm.org/D68333

llvm-svn: 373606
2019-10-03 14:52:33 +00:00
George Rimar 9f6cf2a081 Revert r373598 "[yaml2obj/obj2yaml] - Add support for SHT_LLVM_ADDRSIG sections."
It broke BB:
http://lab.llvm.org:8011/builders/clang-x86_64-debian-fast/builds/18655/steps/test/logs/stdio

llvm-svn: 373599
2019-10-03 14:04:47 +00:00
George Rimar 32cbabfecb [yaml2obj/obj2yaml] - Add support for SHT_LLVM_ADDRSIG sections.
SHT_LLVM_ADDRSIG is described here:
https://llvm.org/docs/Extensions.html#sht-llvm-addrsig-section-address-significance-table

This patch teaches tools to dump them and to parse the YAML declarations of such sections.

Differential revision: https://reviews.llvm.org/D68333

llvm-svn: 373598
2019-10-03 13:57:08 +00:00
George Rimar 6fa696fb08 [yaml2obj] - Alow Size tag for describing SHT_HASH sections.
This is a follow-up for D68085 which allows using "Size"
tag together with "Content" tag or alone.

Differential revision: https://reviews.llvm.org/D68216

llvm-svn: 373473
2019-10-02 13:52:37 +00:00
George Rimar e5163ebf8d [yaml2obj/obj2yaml] - Add support for SHT_HASH sections.
SHT_HASH specification is:
http://www.sco.com/developers/gabi/latest/ch5.dynamic.html#hash

In short the format is the following: it has 2 uint32 fields
in its header: nbucket and nchain followed by (nbucket + nchain)
uint32 values.

This patch allows dumping and parsing such sections.

Differential revision: https://reviews.llvm.org/D68085

llvm-svn: 373315
2019-10-01 09:45:59 +00:00
George Rimar cfc2bccfd8 [yaml2elf] - Support describing .stack_sizes sections using unique suffixes.
Currently we can't use unique suffixes in section names to describe
stack sizes sections. E.g. '.stack_sizes [1]' will be treated as a regular section.
This happens because we recognize stack sizes section by name and
do not yet drop the suffix before the check.

The patch fixes it.

Differential revision: https://reviews.llvm.org/D68018

llvm-svn: 372853
2019-09-25 12:09:30 +00:00
George Rimar f302436a0a [yaml2obj] - Add a Size field for StackSizesSection.
It is a follow-up requested in the review comment
for D67757. Allows to use Content + Size or just Size
when describing .stack_sizes sections in YAML document

Differential revision: https://reviews.llvm.org/D67958

llvm-svn: 372845
2019-09-25 11:40:11 +00:00
George Rimar 1a219aa8df [yaml2obj/obj2yaml] - Add support for .stack_sizes sections.
.stack_sizes is a SHT_PROGBITS section that contains pairs of
<address (4/8 bytes), stack size (uleb128)>.

This patch teach tools to parse and dump it.

Differential revision: https://reviews.llvm.org/D67757

llvm-svn: 372762
2019-09-24 14:22:37 +00:00
George Rimar 4d69967f44 [yaml2obj/obj2yaml] - Do not trigger llvm_unreachable when dumping/parsing relocations and e_machine is unsupported.
Currently when e_machine is set to something that is not supported by YAML lib,
then tools fail with llvm_unreachable.

In this patch I allow them to handle relocations in this case.
It can be used to dump and create objects for broken or unsupported targets.

Differential revision: https://reviews.llvm.org/D67657

llvm-svn: 372377
2019-09-20 09:15:36 +00:00
George Rimar 82d83733dd [obj2yaml] - Support PPC64 relocation types.
We do not support them and fail with llvm_unreachable currently.
This is not the only target we do not support and also seems we are missing
the tests for those we have already. But I needed this one for another patch,
so posted it separatelly.

Relocation names are taken from llvm\include\llvm\BinaryFormat\ELFRelocs\PowerPC64.def

Differential revision: https://reviews.llvm.org/D67615

llvm-svn: 372109
2019-09-17 12:00:55 +00:00
George Rimar cfc0ba3852 [yaml2obj/obj2yaml] - Allow setting an arbitrary values for e_machine.
Currently we only allow using a known named constants
for `Machine` field in YAML documents.

This patch allows using any numbers (valid or "unknown")
and adds test cases for current and new functionality.

With this it is possible to write a test cases for really unknown
EM_* targets.

Differential revision: https://reviews.llvm.org/D67652

llvm-svn: 372108
2019-09-17 11:51:26 +00:00
Fangrui Song d20c41dd31 [yaml2obj] Rename SHOffset (e_shoff) field to SHOff. NFC
`struct Elf*_Shdr` has a field `sh_offset`, named `ShOffset` in
llvm::ELFYAML::Section. Rename SHOffset (e_shoff) to SHOff to prevent confusion.

Reviewed By: grimar

Differential Revision: https://reviews.llvm.org/D67254

llvm-svn: 371185
2019-09-06 09:23:17 +00:00
Fangrui Song 9d2504b6d8 [llvm-readobj][yaml2obj] Support SHT_LLVM_SYMPART, SHT_LLVM_PART_EHDR and SHT_LLVM_PART_PHDR
See http://lists.llvm.org/pipermail/llvm-dev/2019-February/130583.html
and D60242 for the lld partition feature.

This patch:

* Teaches yaml2obj to parse the 3 section types.
* Teaches llvm-readobj/llvm-readelf to dump the 3 section types.

There is no test for SHT_LLVM_DEPENDENT_LIBRARIES in llvm-readobj. Add
it as well.

Reviewed By: thakis

Differential Revision: https://reviews.llvm.org/D67228

llvm-svn: 371157
2019-09-06 00:53:28 +00:00
George Rimar e7b4d20998 Recommit r371023 "[lib/ObjectYAML] - Stop calling error(1) when mapping the st_other field of a symbol."
Fix: added missing return "return 0;"

Original commit message:
This eliminates one of the error(1) call in this lib.
It is different from the others because happens on a fields mapping stage
and can be easily fixed.

Differential revision: https://reviews.llvm.org/D67150

llvm-svn: 371030
2019-09-05 08:52:26 +00:00
George Rimar faa2a08987 Revert r371023 "[lib/ObjectYAML] - Stop calling error(1) when mapping the st_other field of a symbol." (2)
Forgot to revert the cpp file.

llvm-svn: 371025
2019-09-05 08:39:44 +00:00
George Rimar 2c9c432256 [lib/ObjectYAML] - Stop calling error(1) when mapping the st_other field of a symbol.
This eliminates one of the error(1) call in this lib.
It is different from the others because happens on a fields mapping stage
and can be easily fixed.

Differential revision: https://reviews.llvm.org/D67150

llvm-svn: 371023
2019-09-05 08:28:43 +00:00
Fangrui Song 441d450115 [yaml2obj] Support PT_GNU_STACK and PT_GNU_RELRO
PT_GNU_STACK is used in an llvm-objcopy test.

I plan to use PT_GNU_RELRO in a patch to improve nested segment
processing in llvm-objcopy (PR42963).

Reviewed By: grimar

Differential Revision: https://reviews.llvm.org/D67146

llvm-svn: 370857
2019-09-04 09:19:31 +00:00
George Rimar 86cc736df1 [yaml2obj] - Allow overriding sh_name fields of the sections.
This is in line with the previous changes which allowed to
override the sh_offset/sh_size and useful for writing test cases.

Differential revision: https://reviews.llvm.org/D66998

llvm-svn: 370633
2019-09-02 09:47:17 +00:00
George Rimar 4e71702cd4 [yaml2obj][obj2yaml] - Use a single "Other" field instead of "Other", "Visibility" and "StOther".
Currenly we can encode the 'st_other' field of symbol using 3 fields.
'Visibility' is used to encode STV_* values.
'Other' is used to encode everything except the visibility, but it can't handle arbitrary values.
'StOther' is used to encode arbitrary values when 'Visibility'/'Other' are not helpfull enough.

'st_other' field is used to encode symbol visibility and platform-dependent
flags and values. Problem to encode it is that it consists of Visibility part (STV_* values)
which are enumeration values and the Other part, which is different and inconsistent.

For MIPS the Other part contains flags for all STO_MIPS_* values except STO_MIPS_MIPS16.
(Like comment in ELFDumper says: "Someones in their infinite wisdom decided to make
STO_MIPS_MIPS16 flag overlapped with other ST_MIPS_xxx flags."...)

And for PPC64 the Other part might actually encode any value.

This patch implements custom logic for handling the st_other and removes
'Visibility' and 'StOther' fields.

Here is an example of a new YAML style this patch allows:

- Name:  foo
  Other: [ 0x4 ]
- Name:  bar
  Other: [ STV_PROTECTED, 4 ]
- Name:  zed
  Other: [ STV_PROTECTED, STO_MIPS_OPTIONAL, 0xf8 ]

Differential revision: https://reviews.llvm.org/D66886

llvm-svn: 370472
2019-08-30 13:39:22 +00:00
Vlad Tsyrklevich b8a96f4bf5 Reland "[yaml2obj] - Don't allow setting StOther and Other/Visibility at the same time."
This relands this commit, I mistakenly reverted the original change
thinking it was the cause of the observed MSan failures but it was not.

llvm-svn: 370206
2019-08-28 14:04:09 +00:00
Vlad Tsyrklevich aba62e9c00 Revert "[yaml2obj] - Don't allow setting StOther and Other/Visibility at the same time."
This reverts commit r370032, it was causing check-llvm failures on
sanitizer-x86_64-linux-bootstrap-msan

llvm-svn: 370198
2019-08-28 13:15:08 +00:00
George Rimar 7a2e21d9f4 [yaml2obj] - Don't allow setting StOther and Other/Visibility at the same time.
This is a follow up discussed in the comments of D66583.

Currently, if for example, we have both StOther and Other set in YAML document for a symbol,
then yaml2obj reports an "unknown key 'Other'" error.
It happens because 'mapOptional()' is never called for 'Other/Visibility' in this case,
leaving those unhandled.

This message does not describe the reason of the error well. This patch fixes it.

Differential revision: https://reviews.llvm.org/D66642

llvm-svn: 370032
2019-08-27 09:58:39 +00:00
George Rimar 668b11b2c8 [yaml2obj] - Allow setting the symbol st_other field to any integer.
st_other field of a symbol usually contains its visibility.
Other bits are usually 0, though some targets, like
MIPS can set them using the named bit field values.

Problem is that there is no way to set an arbitrary value now,
though that might be useful for our test cases.

In this patch I introduced a way to set st_other to any numeric
value using the new StOther field.
I added a test and simplified the existent one to show the effect/benefit

Differential revision: https://reviews.llvm.org/D66583

llvm-svn: 369742
2019-08-23 09:31:07 +00:00
George Rimar d3963051c4 [yaml2obj/obj2yaml] - Add a basic support for extended section indexes.
In some cases a symbol might have section index == SHN_XINDEX.
This is an escape value indicating that the actual section header index
is too large to fit in the containing field.
Then the SHT_SYMTAB_SHNDX section is used. It contains the 32bit values
that stores section indexes.

ELF gABI says that there can be multiple SHT_SYMTAB_SHNDX sections,
i.e. for example one for .symtab and one for .dynsym
(1) https://groups.google.com/forum/#!topic/generic-abi/-XJAV5d8PRg
(2) DT_SYMTAB_SHNDX: http://www.sco.com/developers/gabi/latest/ch5.dynamic.html

In this patch I am only supporting a single SHT_SYMTAB_SHNDX associated
with a .symtab. This is a more or less common case which is used a few tests I saw in LLVM.

I decided not to create the SHT_SYMTAB_SHNDX section as "implicit",
but implement is like a kind of regular section for now.
i.e. tools do not recreate this section or its content, like they do for
symbol table sections, for example. That should allow to write all kind of
possible broken test cases for our needs and keep the output closer to requested.

Differential revision: https://reviews.llvm.org/D65446

llvm-svn: 368272
2019-08-08 09:49:05 +00:00
George Rimar eb41f7f081 [yaml2obj] - Allow overriding the sh_size field.
There is no way to set broken sh_size field currently
for sections. It can be usefull for writing the
test cases. 

Differential revision: https://reviews.llvm.org/D64401

llvm-svn: 365766
2019-07-11 12:59:29 +00:00
Stanislav Mekhanoshin 22b2c3d651 [AMDGPU] gfx908 target
Differential Revision: https://reviews.llvm.org/D64429

llvm-svn: 365525
2019-07-09 18:10:06 +00:00
George Rimar 9df825f429 [yaml2obj] - Allow overriding sh_offset field from the YAML.
Some of our test cases are using objects which
has sections with a broken sh_offset field.

There was no way to set it from YAML until this patch.

Differential revision: https://reviews.llvm.org/D63879

llvm-svn: 364898
2019-07-02 10:20:12 +00:00
George Rimar 687d47c2b0 [yaml2obj] - Allow overriding e_shentsize, e_shoff, e_shnum and e_shstrndx fields in the YAML.
This allows setting different values for e_shentsize, e_shoff, e_shnum
and e_shstrndx fields and is useful for producing broken inputs for various
test cases.

Differential revision: https://reviews.llvm.org/D63771

llvm-svn: 364517
2019-06-27 11:08:42 +00:00
Nicolai Haehnle 08e8cb5760 AMDGPU/MC: Add .amdgpu_lds directive
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
2019-06-25 11:51:35 +00:00