Similar to commit 28fcafb50274be2520117eacb0a886adafefe59d (2011) for
MachObjectWriter. MCWinCOFFStreamer can now access WinCOFFObjectWriter
directly without holding object file format specific inforamtion in
MCAssembler (e.g. IncrementalLinkerCompatible).
This restores 63ec52f867ada8d841dd872acf3d0cb62e2a99e8 and
46f7929879a59ec72dc75679b4201e2d314efba9, NFC changes that were
unnecessarily reverted.
This completes the work that merges MCAsmLayout into MCAssembler.
Pull Request: https://github.com/llvm/llvm-project/pull/97449
and replace MCAssembler::Layout with a bool.
This mostly completes "[MC] Start merging MCAsmLayout into MCAssembler".
Note: BOLT used a dummy `MCAsmLayout` to call `getSymbolOffset`, which
is technically not supported. There is some discussion in
https://reviews.llvm.org/D154604 .
The revert f80a4072ced41b52363c63df28fea9a649f7f89e is incorrect and
actually broke bots.
This reverts commit c72cb2766cec0ac519a051780ae5aed42485e012.
The patch was not reviewed, and this assertion guards against incorrect
values for symbols if the linker decides to modify the layout as it
happens on some platforms. getSymbolOffset() is used for code size
estimation, among others.
Reverting for now, until we get proper code review and undersatnding of
the implications.
BOLT used a dummy `MCAsmLayout` to call `getSymbolOffset`, which is
technically not supported. There is some discussion in
https://reviews.llvm.org/D154604 that this is not ideal.
For now, remove the assert.
The assert was added by bbb50369a149d9a7d1f91efaaabf75c260a220c7.
Follow-up to 2c1fb411ce3aed148a278660d215e0f88ff9b9be.
SectionOrder is Mach-O specific to place zerofill sections after
non-zerofill sections in the object writer.
Follow-up to 10c894cffd0f4bef21b54a43b5780240532e44cf.
MCAsmLayout, introduced by ac8a95498a99eb16dff9d3d0186616645d200b6e
(2010), provides APIs to compute fragment/symbol/section offsets.
The separate class is cumbersome and passing it around has overhead.
Let's remove it as the underlying implementation is tightly coupled with
MCAsmLayout anyway.
Some forwarders are added to ease migration.
8d736236d36ca5c98832b7631aea2e538f6a54aa (2015) moved these MCAsmLayout
functions to MCFragment.cpp, but the original placement is better as
these functions are tightly coupled with MCAssembler.cpp.
RelaxAll/SubsectionsViaSyms are used more frequently then vector members
like Sections/Symbols. The size of MCAssembler doesn't particularly
matter, so avoid bit fields.
MCAssembler::layout ensures that every section has at least one
fragment, which simplifies MCAsmLayout::getSectionAddressSize (see
e73353c7201a3080851d99a16f5fe2c17f7697c6 from 2010). It's better to
ensure the condition is satisfied at create time (COFF, GOFF, Mach-O) to
simplify more fragment processing.
This commit removes the complexity introduced by pending labels in
https://reviews.llvm.org/D5915 by using a simpler approach. D5915 aimed
to ensure padding placement before `.Ltmp0` for the following code, but
at the cost of expensive per-instruction `flushPendingLabels`.
```
// similar to llvm/test/MC/X86/AlignedBundling/labeloffset.s
.bundle_lock align_to_end
calll .L0$pb
.bundle_unlock
.L0$pb:
popl %eax
.Ltmp0: //// padding should be inserted before this label instead of after
addl $_GLOBAL_OFFSET_TABLE_+(.Ltmp0-.L0$pb), %eax
```
(D5915 was adjusted by https://reviews.llvm.org/D8072 and
https://reviews.llvm.org/D71368)
This patch achieves the same goal by setting the offset of the empty
MCDataFragment (`Prev`) in `layoutBundle`. This eliminates the need for
pending labels and simplifies the code.
llvm/test/MC/MachO/pending-labels.s (D71368): relocation symbols are
changed, but the result is still supported by linkers.
When both aligned bundling and RelaxAll are enabled, bundle padding is
directly written into fragments (https://reviews.llvm.org/D8072).
(The original motivation was memory usage, which has been achieved from
different angles with recent assembler improvement).
The code presents challenges with the work to replace fragment
representation (e.g. #94950#95077). This patch removes the special
handling. RelaxAll still works but the behavior seems slightly different
as revealed by 2 changed tests. However, most `-mc-relax-all` tests are
unchanged.
RelaxAll used to be the default for clang -O0. This mode has significant
code size drawbacks and newer Clang doesn't use it (#90013).
---
flushPendingLabels: The FOffset parameter can be removed: pending labels
will be assigned to the incoming fragment at offset 0.
Pull Request: https://github.com/llvm/llvm-project/pull/95188
`allocFragment` might be changed to a placement new when the allocation
strategy changes.
`allocInitialFragment` is to deduplicate the following pattern
```
auto *F = new MCDataFragment();
Result->addFragment(*F);
F->setParent(Result);
```
Pull Request: https://github.com/llvm/llvm-project/pull/95197
Fragments are allocated with `operator new` and stored in an ilist with
Prev/Next/Parent pointers. A more efficient representation would be an
array of fragments without the overhead of Prev/Next pointers.
As the first step, replace ilist with singly-linked lists.
* `getPrevNode` uses have been eliminated by previous changes.
* The last use of the `Prev` pointer remains: for each subsection, there is an insertion point and
the current insertion point is stored at `CurInsertionPoint`.
* `HexagonAsmBackend::finishLayout` needs a backward iterator. Save all
fragments within `Frags`. Hexagon programs are usually small, and the
performance does not matter that much.
To eliminate `Prev`, change the subsection representation to
singly-linked lists for subsections and a pointer to the active
singly-linked list. The fragments from all subsections will be chained
together at layout time.
Since fragment lists are disconnected before layout time, we can remove
`MCFragment::SubsectionNumber` (https://reviews.llvm.org/D69411). The
current implementation of `AttemptToFoldSymbolOffsetDifference` requires
future improvement for robustness.
Pull Request: https://github.com/llvm/llvm-project/pull/95077
Lazy relaxation caused hash table lookups (`getFragmentOffset`) and
complex use/compute interdependencies. Some expressions involding
forward declared symbols (e.g. `subsection-if.s`) cannot be computed.
Recursion detection requires complex `IsBeingLaidOut`
(https://reviews.llvm.org/D79570).
D76114's `invalidateFragmentsFrom` makes lazy relaxation even less
useful.
Switch to eager relaxation to greatly simplify code and resolve these
issues. This change also removes a `getPrevNode` use, which makes it
more feasible to replace the fragment representation, which might yield
a large peak RSS win.
Minor downsides: The number of section relaxations may increase (offset
by avoiding the hash table lookup). For relax-recompute-align.s, the
computed layout is not optimal.
Fix the bug where merge-fdata unconditionally outputs boltedcollection
line, regardless of whether input files have it set.
Test Plan:
Added bolt/test/X86/merge-fdata-nobat-mode.test which fails without this
fix.
1, Follow RISCV 1df5ea29 to support generates relocs for .uleb128 which
can not be folded. Unlike RISCV, the located content of LoongArch should
be zero. LoongArch fixup uleb128 value by in-place addition and
subtraction reloc types named R_LARCH_{ADD,SUB}_ULEB128. The located
content can affect the result and R_LARCH_ADD_ULEB128 has enough info to
represent the first symbol value, so it needs to be set to zero.
2, Force relocs if sym is not in section so that it can emit relocs for
external symbol.
Fixes:
https://github.com/llvm/llvm-project/pull/72960#issuecomment-1866844679
