Today `-split-machine-functions` and `-fbasic-block-sections={all,list}`
cannot be combined with `-basic-block-sections=labels` (the labels
option will be ignored).
The inconsistency comes from the way basic block address map -- the
underlying mechanism for basic block labels -- encodes basic block
addresses
(https://lists.llvm.org/pipermail/llvm-dev/2020-July/143512.html).
Specifically, basic block offsets are computed relative to the function
begin symbol. This relies on functions being contiguous which is not the
case for MFS and basic block section binaries. This means Propeller
cannot use binary profiles collected from these binaries, which limits
the applicability of Propeller for iterative optimization.
To make the `SHT_LLVM_BB_ADDR_MAP` feature work with basic block section
binaries, we propose modifying the encoding of this section as follows.
First let us review the current encoding which emits the address of each
function and its number of basic blocks, followed by basic block entries
for each basic block.
| | |
|--|--|
| Address of the function | Function Address |
| Number of basic blocks in this function | NumBlocks |
| BB entry 1
| BB entry 2
| ...
| BB entry #NumBlocks
To make this work for basic block sections, we treat each basic block
section similar to a function, except that basic block sections of the
same function must be encapsulated in the same structure so we can map
all of them to their single function.
We modify the encoding to first emit the number of basic block sections
(BB ranges) in the function. Then we emit the address map of each basic
block section section as before: the base address of the section, its
number of blocks, and BB entries for its basic block. The first section
in the BB address map is always the function entry section.
| | |
|--|--|
| Number of sections for this function | NumBBRanges |
| Section 1 begin address | BaseAddress[1] |
| Number of basic blocks in section 1 | NumBlocks[1] |
| BB entries for Section 1
|..................|
| Section #NumBBRanges begin address | BaseAddress[NumBBRanges] |
| Number of basic blocks in section #NumBBRanges |
NumBlocks[NumBBRanges] |
| BB entries for Section #NumBBRanges
The encoding of basic block entries remains as before with the minor
change that each basic block offset is now computed relative to the
begin symbol of its containing BB section.
This patch adds a new boolean codegen option `-basic-block-address-map`.
Correspondingly, the front-end flag `-fbasic-block-address-map` and LLD
flag `--lto-basic-block-address-map` are introduced.
Analogously, we add a new TargetOption field `BBAddrMap`. This means BB
address maps are either generated for all functions in the compiling
unit, or for none (depending on `TargetOptions::BBAddrMap`).
This patch keeps the functionality of the old
`-fbasic-block-sections=labels` option but does not remove it. A
subsequent patch will remove the obsolete option.
We refactor the `BasicBlockSections` pass by separating the BB address
map and BB sections handing to their own functions (named
`handleBBAddrMap` and `handleBBSections`). `handleBBSections` renumbers
basic blocks and places them in their assigned sections.
`handleBBAddrMap` is invoked after `handleBBSections` (if requested) and
only renumbers the blocks.
- New tests added:
- Two tests basic-block-address-map-with-basic-block-sections.ll and
basic-block-address-map-with-mfs.ll to exercise the combination of
`-basic-block-address-map` with `-basic-block-sections=list` and
'-split-machine-functions`.
- A driver sanity test for the `-fbasic-block-address-map` option
(basic-block-address-map.c).
- An LLD test for testing the `--lto-basic-block-address-map` option.
This reuses the LLVM IR from `lld/test/ELF/lto/basic-block-sections.ll`.
- Renamed and modified the two existing codegen tests for basic block
address map (`basic-block-sections-labels-functions-sections.ll` and
`basic-block-sections-labels.ll`)
- Removed `SHT_LLVM_BB_ADDR_MAP_V0` tests. Full deprecation of
`SHT_LLVM_BB_ADDR_MAP_V0` and `SHT_LLVM_BB_ADDR_MAP` version less than 2
will happen in a separate PR in a few months.
We had specified that `readBBAddrMap` will always keep PGOAnalyses and
BBAddrMaps the same length on success.
365fbbfbcf/llvm/include/llvm/Object/ELFObjectFile.h (L116-L117)
It turns out that this is not currently the case when no analyses exist
in a function. No test had caught it.
We also should not append PGOBBEntries when there is no BBFreq or
BrProb.
This patch adds:
* tests that PGOAnalyses and BBAddrMaps are same length even when no
analyses are enabled
* fixes decode so that PGOAnalyses and BBAddrMaps are same length
* updates test to not emit unnecessary PGOBBEntries
* fixes decode to not emit PGOBBEntries when unnecessary
Reviewed in PR (#71750). A part of [RFC - PGO Accuracy Metrics: Emitting and Evaluating Branch
and Block
Analysis](https://discourse.llvm.org/t/rfc-pgo-accuracy-metrics-emitting-and-evaluating-branch-and-block-analysis/73902).
This PR adds the PGOAnalysisMap data structure and implements encoding and
decoding through Object and ObjectYAML along with associated tests. When
emitted into the bb-addr-map section, each function is followed by the associated
pgo-analysis-map for that function. The emitting of each analysis in the map is
controlled by a bit in the bb-addr-map feature byte. All existing bb-addr-map
code can ignore the pgo-analysis-map if the caller does not request the data.
In preparation for removing the `#include "llvm/ADT/StringExtras.h"`
from the header to source file of `llvm/Support/Error.h`, first add in
all the missing includes that were previously included transitively
through this header.
This patch encapsulates the encoding and decoding logic of basic block metadata into the Metadata struct, and also reduces the decoded size of `SHT_LLVM_BB_ADDR_MAP` section.
The patch would've looked more readable if we could use designated initializer, but that is a c++20 feature.
Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D148360
Currently when using the LLVM tools (eg llvm-readobj, llvm-objdump) to
find information about basic block locations using the propeller tooling
in relocatable object files function addresses are not mapped properly
which causes problems. In llvm-readobj this means that incorrect
function names will be pulled. In llvm-objdum this means that most BBs
won't show up in the output if --symbolize-operands is used. This patch
changes the behavior of decodeBBAddrMap to trace through relocations
to get correct function addresses if it is going through a relocatable
object file. This fixes the behavior in both tools and also other
consumers of decodeBBAddrMap. Some helper functions have been added
in/refactoring done to aid in grabbing BB address map sections now that
in some cases both relocation and BB address map sections need to be
obtained at the same time.
Regression tests moved around/added.
Differential Revision: https://reviews.llvm.org/D143841
This refactoring will allow for this utility function to be used in
other places in the codebase outside of the llvm-readobj tool.
Reviewed By: jhenderson, rahmanl
Differential Revision: https://reviews.llvm.org/D144783
Let Propeller use specialized IDs for basic blocks, instead of MBB number.
This allows optimizations not just prior to asm-printer, but throughout the entire codegen.
This patch only implements the functionality under the new `LLVM_BB_ADDR_MAP` version, but the old version is still being used. A later patch will change the used version.
####Background
Today Propeller uses machine basic block (MBB) numbers, which already exist, to map native assembly to machine IR. This is done as follows.
- Basic block addresses are captured and dumped into the `LLVM_BB_ADDR_MAP` section just before the AsmPrinter pass which writes out object files. This ensures that we have a mapping that is close to assembly.
- Profiling mapping works by taking a virtual address of an instruction and looking up the `LLVM_BB_ADDR_MAP` section to find the MBB number it corresponds to.
- While this works well today, we need to do better when we scale Propeller to target other Machine IR optimizations like spill code optimization. Register allocation happens earlier in the Machine IR pipeline and we need an annotation mechanism that is valid at that point.
- The current scheme will not work in this scenario because the MBB number of a particular basic block is not fixed and changes over the course of codegen (via renumbering, adding, and removing the basic blocks).
- In other words, the volatile MBB numbers do not provide a one-to-one correspondence throughout the lifetime of Machine IR. Profile annotation using MBB numbers is restricted to a fixed point; only valid at the exact point where it was dumped.
- Further, the object file can only be dumped before AsmPrinter and cannot be dumped at an arbitrary point in the Machine IR pass pipeline. Hence, MBB numbers are not suitable and we need something else.
####Solution
We propose using fixed unique incremental MBB IDs for basic blocks instead of volatile MBB numbers. These IDs are assigned upon the creation of machine basic blocks. We modify `MachineFunction::CreateMachineBasicBlock` to assign the fixed ID to every newly created basic block. It assigns `MachineFunction::NextMBBID` to the MBB ID and then increments it, which ensures having unique IDs.
To ensure correct profile attribution, multiple equivalent compilations must generate the same Propeller IDs. This is guaranteed as long as the MachineFunction passes run in the same order. Since the `NextBBID` variable is scoped to `MachineFunction`, interleaving of codegen for different functions won't cause any inconsistencies.
The new encoding is generated under the new version number 2 and we keep backward-compatibility with older versions.
####Impact on Size of the `LLVM_BB_ADDR_MAP` Section
Emitting the Propeller ID results in a 23% increase in the size of the `LLVM_BB_ADDR_MAP` section for the clang binary.
Reviewed By: tmsriram
Differential Revision: https://reviews.llvm.org/D100808
Use deduction guides instead of helper functions.
The only non-automatic changes have been:
1. ArrayRef(some_uint8_pointer, 0) needs to be changed into ArrayRef(some_uint8_pointer, (size_t)0) to avoid an ambiguous call with ArrayRef((uint8_t*), (uint8_t*))
2. CVSymbol sym(makeArrayRef(symStorage)); needed to be rewritten as CVSymbol sym{ArrayRef(symStorage)}; otherwise the compiler is confused and thinks we have a (bad) function prototype. There was a few similar situation across the codebase.
3. ADL doesn't seem to work the same for deduction-guides and functions, so at some point the llvm namespace must be explicitly stated.
4. The "reference mode" of makeArrayRef(ArrayRef<T> &) that acts as no-op is not supported (a constructor cannot achieve that).
Per reviewers' comment, some useless makeArrayRef have been removed in the process.
This is a follow-up to https://reviews.llvm.org/D140896 that introduced
the deduction guides.
Differential Revision: https://reviews.llvm.org/D140955
Add file with Xtensa ELF relocations. Add Xtensa support to ELF.h,
ELFObject.h and ELFYAML.cpp. Add simple test of Xtensa ELF representation in YAML.
Differential Revision: https://reviews.llvm.org/D64827
Let Propeller use specialized IDs for basic blocks, instead of MBB number.
This allows optimizations not just prior to asm-printer, but throughout the entire codegen.
This patch only implements the functionality under the new `LLVM_BB_ADDR_MAP` version, but the old version is still being used. A later patch will change the used version.
####Background
Today Propeller uses machine basic block (MBB) numbers, which already exist, to map native assembly to machine IR. This is done as follows.
- Basic block addresses are captured and dumped into the `LLVM_BB_ADDR_MAP` section just before the AsmPrinter pass which writes out object files. This ensures that we have a mapping that is close to assembly.
- Profiling mapping works by taking a virtual address of an instruction and looking up the `LLVM_BB_ADDR_MAP` section to find the MBB number it corresponds to.
- While this works well today, we need to do better when we scale Propeller to target other Machine IR optimizations like spill code optimization. Register allocation happens earlier in the Machine IR pipeline and we need an annotation mechanism that is valid at that point.
- The current scheme will not work in this scenario because the MBB number of a particular basic block is not fixed and changes over the course of codegen (via renumbering, adding, and removing the basic blocks).
- In other words, the volatile MBB numbers do not provide a one-to-one correspondence throughout the lifetime of Machine IR. Profile annotation using MBB numbers is restricted to a fixed point; only valid at the exact point where it was dumped.
- Further, the object file can only be dumped before AsmPrinter and cannot be dumped at an arbitrary point in the Machine IR pass pipeline. Hence, MBB numbers are not suitable and we need something else.
####Solution
We propose using fixed unique incremental MBB IDs for basic blocks instead of volatile MBB numbers. These IDs are assigned upon the creation of machine basic blocks. We modify `MachineFunction::CreateMachineBasicBlock` to assign the fixed ID to every newly created basic block. It assigns `MachineFunction::NextMBBID` to the MBB ID and then increments it, which ensures having unique IDs.
To ensure correct profile attribution, multiple equivalent compilations must generate the same Propeller IDs. This is guaranteed as long as the MachineFunction passes run in the same order. Since the `NextBBID` variable is scoped to `MachineFunction`, interleaving of codegen for different functions won't cause any inconsistencies.
The new encoding is generated under the new version number 2 and we keep backward-compatibility with older versions.
####Impact on Size of the `LLVM_BB_ADDR_MAP` Section
Emitting the Propeller ID results in a 23% increase in the size of the `LLVM_BB_ADDR_MAP` section for the clang binary.
Reviewed By: tmsriram
Differential Revision: https://reviews.llvm.org/D100808
Add ELFObjectFileBase::getLoongArchFeatures, and return the proper ELF
relative reloc type for LoongArch.
Reviewed By: MaskRay, SixWeining
Differential Revision: https://reviews.llvm.org/D138016
Currently we use the `.llvm.offloading` section to store device-side
objects inside the host, creating a fat binary. The contents of these
sections is currently determined by the name of the section while it
should ideally be determined by its type. This patch adds the new
`SHT_LLVM_OFFLOADING` section type to the ELF section types. Which
should make it easier to identify this specific data format.
Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D129052
This is a resurrection of D106421 with the change that it keeps backward-compatibility. This means decoding the previous version of `LLVM_BB_ADDR_MAP` will work. This is required as the profile mapping tool is not released with LLVM (AutoFDO). As suggested by @jhenderson we rename the original section type value to `SHT_LLVM_BB_ADDR_MAP_V0` and assign a new value to the `SHT_LLVM_BB_ADDR_MAP` section type. The new encoding adds a version byte to each function entry to specify the encoding version for that function. This patch also adds a feature byte to be used with more flexibility in the future. An use-case example for the feature field is encoding multi-section functions more concisely using a different format.
Conceptually, the new encoding emits basic block offsets and sizes as label differences between each two consecutive basic block begin and end label. When decoding, offsets must be aggregated along with basic block sizes to calculate the final offsets of basic blocks relative to the function address.
This encoding uses smaller values compared to the existing one (offsets relative to function symbol).
Smaller values tend to occupy fewer bytes in ULEB128 encoding. As a result, we get about 17% total reduction in the size of the bb-address-map section (from about 11MB to 9MB for the clang PGO binary).
The extra two bytes (version and feature fields) incur a small 3% size overhead to the `LLVM_BB_ADDR_MAP` section size.
Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D121346
Fix#54456: `objcopy --only-keep-debug` produces a linked image with invalid
empty dynamic section. llvm-objdump -p currently reports an error which seems
excessive.
```
% llvm-readelf -l a.out
llvm-readelf: warning: 'a.out': no valid dynamic table was found
...
```
Follow the spirit of llvm-readelf -l (D64472) and report a warning instead.
This allows later files to be dumped despite warnings for an input file, and
improves objdump compatibility in that the exit code is now 0 instead of 1.
```
% llvm-objdump -p a.out # new behavior
...
Program Header:
llvm-objdump: warning: 'a.out': invalid empty dynamic section
% objdump -p a.out
...
Dynamic Section:
```
Reviewed By: jhenderson, raj.khem
Differential Revision: https://reviews.llvm.org/D122505
This patch adds necessary definitions for LoongArch ELF files, including
relocation types. Also adds initial support to ELFYaml, llvm-objdump,
and llvm-readobj in order to work with LoongArch ELFs.
Differential revision: https://reviews.llvm.org/D115859
Change getELFRelativeRelocationType() to return R_VE_RELATIVE
as a preparation of lld for VE.
Reviewed By: simoll
Differential Revision: https://reviews.llvm.org/D115592
The only binary-format-related field in the BBAddrMap structure is the function address (`Addr`), which will use uint64_t in 64B format and uint32_t in 32B format. This patch changes it to use uint64_t in both formats.
This allows non-templated use of the struct, at the expense of a marginal additional size overhead for the 32-bit format. The size of the BB address map section does not change.
Differential Revision: https://reviews.llvm.org/D112679
The MSP430 ABI supports build attributes for specifying
the ISA, code model, data model and enum size in ELF object files.
Differential Revision: https://reviews.llvm.org/D107969
- Add the M68k-specific MC layer implementation
- Add ELF support for M68k
- Add M68k-specifc CC and reloc
TODO: Currently AsmParser and disassembler are not implemented yet.
Please use this bug to track the status:
https://bugs.llvm.org/show_bug.cgi?id=48976
Authors: myhsu, m4yers, glaubitz
Differential Revision: https://reviews.llvm.org/D88390
A simple refactoring patch which let us use `DataExtractor::getSLEB128` rather than using a lambda function.
Differential Revision: https://reviews.llvm.org/D95158
This is https://bugs.llvm.org/show_bug.cgi?id=45698.
Specification says that
"Loadable segment entries in the program header table appear
in ascending order, sorted on the p_vaddr member."
Our `toMappedAddr()` relies on this condition. This patch
adds a warning when the sorting order of loadable segments is wrong.
In this case we force segments sorting and that allows
`toMappedAddr()` to work as expected.
Differential revision: https://reviews.llvm.org/D92641
This patch lets the bb_addr_map (renamed to __llvm_bb_addr_map) section use a special section type (SHT_LLVM_BB_ADDR_MAP) instead of SHT_PROGBITS. This would help parsers, dumpers and other tools to use the sh_type ELF field to identify this section rather than relying on string comparison on the section name.
Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D88199
`ELFFile<ELFT>` has many methods that take pointers,
though they assume that arguments are never null and
hence could take references instead.
This patch performs such clean-up.
Differential revision: https://reviews.llvm.org/D87385
This is the split part of D86269, which add a new ELF machine flag called EM_CSKY and related relocations.
Some target-specific flags and tests for csky can be added in follow-up patches later.
Differential Revision: https://reviews.llvm.org/D86610
The `decode_relrs` helper is declared as:
`Expected<std::vector<Elf_Rel>> decode_relrs(Elf_Relr_Range relrs) const;`
it never returns an error though and hence can be simplified to return
a vector.
Differential revision: https://reviews.llvm.org/D85302
There is a strange "feature" of the code: it handles all relocations as `Elf_Rela`.
For handling `Elf_Rel` it converts them to `Elf_Rela` and passes `bool IsRela` to
specify the real type everywhere.
A related issue is that the
`decode_relrs` helper in lib/Object has to return `Expected<std::vector<Elf_Rela>>`
because of that, though it could return a vector of `Elf_Rel`.
I think we should just start using templates for relocation types, it makes the code
cleaner and shorter. This patch does it.
Differential revision: https://reviews.llvm.org/D83871
Summary:
Define ELF binary code for VE and modify code where should use this new code.
Depends on D79544.
Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D79545
Check for `DynSecSize % sizeof(Elf_Dyn) != 0` is unneeded in this context.
1. If the .dynamic section is acquired from program headers, the .dynamic
section is "cut off" by
```
makeArrayRef(..., Phdr.p_filesz / sizeof(Elf_Dyn));
DynSeSize = Phdr.p_filesz;
```
2. If the .dynamic section is acquired from section headers, the .dynamic
section is checked in `getSectionContentsAsArray<Elf_Dyn>(&Sec)`.
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D79560
Leverage ARM ELF build attribute section to create ELF attribute section
for RISC-V. Extract the common part of parsing logic for this section
into ELFAttributeParser.[cpp|h] and ELFAttributes.[cpp|h].
Differential Revision: https://reviews.llvm.org/D74023
We might have a crash scenario when we have an invalid DT_STRTAB value
that is larger than the file size. I've added a test case to demonstrate.
Differential revision: https://reviews.llvm.org/D76706
This removes the `getTypeString` from readeobj source because it
almost duplicates the existent method: `ELFFile<ELFT>::getDynamicTagAsString`.
Side effect: now it prints "<unknown:>0xHEXVALUE" instead of "(unknown)" for unknown values.
llvm-readelf before this patch printed:
```
0x0000000012345678 (unknown) 0x8765432187654321
0x000000006abcdef0 (unknown) 0x9988776655443322
0x0000000076543210 (unknown) 0x5555666677778888
```
and now it prints:
```
0x0000000012345678 (<unknown:>0x12345678) 0x8765432187654321
0x000000006abcdef0 (<unknown:>0x6abcdef0) 0x9988776655443322
0x0000000076543210 (<unknown:>0x76543210) 0x5555666677778888
```
GNU reaedlf prints different thing:
```
0x0000000012345678 (<unknown>: 12345678) 0x8765432187654321
0x000000006abcdef0 (Operating System specific: 6abcdef0) 0x9988776655443322
0x0000000076543210 (Processor Specific: 76543210) 0x5555666677778888
```
I am not sure we want to follow GNU here. Even if we do, it should be separate
patch probably. The new output looks better and closer to GNU anyways,
and the code is a bit simpler.
Differential revision: https://reviews.llvm.org/D71835
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
The errors coming from ELF.h are usually not very
useful because they are uninformative. This patch is a
first step to improve the situation.
I tested this patch with a run of check-llvm and found
that few messages are untested. In this patch, I did not
add more tests but marked all such cases with a "TODO" comment.
For all tested messages I extended the error text to
provide more details (see test cases changed).
Differential revision: https://reviews.llvm.org/D64014
llvm-svn: 365183
ELF for the 64-bit Arm Architecture defines two processor-specific dynamic
tags:
DT_AARCH64_BTI_PLT 0x70000001, d_val
DT_AARCH64_PAC_PLT 0x70000003, d_val
These presence of these tags indicate that PLT sequences have been
protected using Branch Target Identification and Pointer Authentication
respectively. The presence of both indicates that the PLT sequences have
been protected with both Branch Target Identification and Pointer
Authentication.
This patch adds the tags and tests for llvm-readobj and yaml2obj.
As some of the processor specific dynamic tags overlap, this patch splits
them up, keeping their original default value if they were not previously
mentioned explicitly in a switch case.
Differential Revision: https://reviews.llvm.org/D62596
llvm-svn: 362493
