```
/// Symbols can be appended with "(.__uniq.xxxx)?.llvm.yyyy" where "xxxx" and
/// "yyyy" are numbers that could change between builds. We need to use the root
/// symbol name before this suffix so these symbols can be matched with profiles
/// which may have different suffixes.
```
Just like what we are doing in BP,
https://github.com/llvm/llvm-project/blob/main/lld/MachO/BPSectionOrderer.cpp#L127
the patch removes the suffixes when parsing the order file and getting
the symbol priority to have a better symbol match.
---------
Co-authored-by: Sharon Xu <sharonxu@fb.com>
Co-authored-by: Ellis Hoag <ellis.sparky.hoag@gmail.com>
With an upcoming change to llvm/ProfileData headers, this file ends up
with both llvm::Reloc in scope as well as the lld::macho::Reloc type
intended for use here. Qualify the use in this file with the intended
namespace to avoid compilation errors.
ICF runs before BPSectionOrderer. When a section is ICF'ed, it seems
that the original sections are marked as not live, but are still kept
around. Prior to this patch, those ICF'ed sections would be passed to BP
and ordered before being skipped when writing the output. Now, these
sections are no longer passed to BP, saving runtime and possibly
improving BP's output.
In a large binary, I found that the number of sections ordered using BP
decreased, while the number of duplicate sections drastically decreased
as expected.
```
Functions for startup: 50755 -> 50520
Functions for compression: 165734 -> 105328
Duplicate functions: 1827231 -> 55230
```
Exposed by the test added in the reverted #120514
* Fix libstdc++/libc++ differences due to nth_element. https://github.com/llvm/llvm-project/pull/125450#issuecomment-2631404178
* Fix LLVM_ENABLE_REVERSE_ITERATION=1 differences
* Fix potential issue in `currentSize += D::getSize(*sections[*sectionIdxs.begin()])` where DenseSet was used, though not covered by a test
The ELF/bp-section-orderer.s test is failing on some buildbots due to
what seems like non-determinism issues, see comments on the original PR
and #125450
Reverting to green the build.
This reverts commit 0154dce8d39d2688b09f4e073fe601099a399365 and
follow-up commits 046dd4b28b9c1a75a96cf63465021ffa9fe1a979 and
c92f20416e6dbbde9790067b80e75ef1ef5d0fa4.
PR #117514 refactored BPSectionOrderer to be used by the ELF port
but introduced some inefficiency:
* BPSectionBase/BPSymbol are wrappers around a single pointer.
The numbers of sections and symbols could be huge, and the extra
allocations are memory inefficient.
* Reconstructing the returned DenseMap (since BPSectionBase != InputSectin)
is wasteful.
This patch refactors BPSectionOrderer with Curiously Recurring Template
Pattern and eliminates the inefficiency. In addition,
`symbolToSectionIdxs` is removed and `rootSymbolToSectionIdxs` building
is moved to lld/MachO: while getting sections for symbols is cheap in
Mach-O, it is awkward and inefficient in the ELF port.
While here, add a file-level comment and replace some `StringMap<*>`
(which copies strings) with `DenseMap<CachedHashStringRef, *>`.
Pull Request: https://github.com/llvm/llvm-project/pull/124482
--order_file, call graph profile, and BalancedPartitioning currently
build the section order vector by decreasing priority (from SIZE_MAX to
0). However, it's conventional to use an increasing key (see
OutputSection::inputOrder).
Switch to increasing priorities, remove the global variable
highestAvailablePriority, and remove the highestAvailablePriority
parameter from BPSectionOrderer. Change size_t to int.
This improves consistenty with the ELF and COFF ports. The ELF port
utilizes negative priorities for --symbol-ordering-file and call graph
profile, and non-negative priorities for --shuffle-sections (no Mach-O
counterpart yet).
Pull Request: https://github.com/llvm/llvm-project/pull/121727
Refactor some code in `BPSectionOrderer.cpp` in preparation for
https://github.com/llvm/llvm-project/pull/107348.
* Rename `constructNodesForCompression()` -> `getUnsForCompression()`
and return a `SmallVector` directly rather than populating a vector
alias
* Pass `duplicateSectionIdxs` as a pointer to make it possible to skip
finding (nearly) duplicate sections
* Combine `duplicate{Function,Data}SectionIdxs` into one variable
* Compute all `BPFunctionNode` vectors at the end (like
`nodesForStartup`)
There should be no functional change.
Add the "Separate" option `--irpgo-profile-sort <profile` instead of
just the "Joined" option `--irpgo-profile-sort=<profile>`. This is
useful if the path has a `,` for some reason which would break when
trying to use `-Wl,--irpgo-profile-sort=<profile-with-comma>`.
While I'm here, use `static_cast<>` instead of the C style cast
introduced in https://github.com/llvm/llvm-project/pull/100627
Add the lld flags `--irpgo-profile-sort=<profile>` and
`--compression-sort={function,data,both}` to order functions to improve
startup time, and functions or data to improve compressed size,
respectively.
We use Balanced Partitioning to determine the best section order using
traces from IRPGO profiles (see
https://discourse.llvm.org/t/rfc-temporal-profiling-extension-for-irpgo/68068
for details) to improve startup time and using hashes of section
contents to improve compressed size.
In our recent LLVM talk (https://www.youtube.com/watch?v=yd4pbSTjwuA),
we showed that this can reduce page faults during startup by 40% on a
large iOS app and we can reduce compressed size by 0.8-3%.
More details can be found in https://dl.acm.org/doi/10.1145/3660635
---------
Co-authored-by: Vincent Lee <thevinster@users.noreply.github.com>
