Similay to
94655dc8ae
The difference is that in LoongArch, the ALIGN is synthesized when the
alignment is >4, (instead of >=4), and the number of bytes inserted is
`sec->addralign - 4`.
Clear `synthesizedAligns` to prevent stray relocations to an unrelated
text section. Enhance the test to check llvm-readelf -r output.
---
Without linker relaxation enabled for a particular relocatable file or
section (e.g., using .option norelax), the assembler will not generate
R_RISCV_ALIGN relocations for alignment directives. This becomes
problematic in a two-stage linking process:
```
ld -r a.o b.o -o ab.o
// b.o is norelax. Its alignment information is lost in ab.o.
ld ab.o -o ab
```
When ab.o is linked into an executable, the preceding relaxed section
(a.o's content) might shrink. Since there's no R_RISCV_ALIGN relocation
in b.o for the linker to act upon, the `.word 0x3a393837` data in b.o
may end up unaligned in the final executable.
To address the issue, this patch inserts NOP bytes and synthesizes an
R_RISCV_ALIGN relocation at the beginning of a text section when the
alignment >= 4.
For simplicity, when RVC is disabled, we synthesize an ALIGN relocation
(addend: 2) for a 4-byte aligned section, allowing the linker to trim
the excess 2 bytes.
See also https://sourceware.org/bugzilla/show_bug.cgi?id=33236
This reverts commit 6f53f1c8d2bdd13e30da7d1b85ed6a3ae4c4a856.
synthesiedAligns is not cleared, leading to stray relocations for
unrelated sections. Revert for now.
Without linker relaxation enabled for a particular relocatable file or
section (e.g., using .option norelax), the assembler will not generate
R_RISCV_ALIGN relocations for alignment directives. This becomes
problematic in a two-stage linking process:
```
ld -r a.o b.o -o ab.o
// b.o is norelax. Its alignment information is lost in ab.o.
ld ab.o -o ab
```
When ab.o is linked into an executable, the preceding relaxed section
(a.o's content) might shrink. Since there's no R_RISCV_ALIGN relocation
in b.o for the linker to act upon, the `.word 0x3a393837` data in b.o
may end up unaligned in the final executable.
To address the issue, this patch inserts NOP bytes and synthesizes an
R_RISCV_ALIGN relocation at the beginning of a text section when the
alignment >= 4.
For simplicity, when RVC is disabled, we synthesize an ALIGN relocation
(addend: 2) for a 4-byte aligned section, allowing the linker to trim
the excess 2 bytes.
See also https://sourceware.org/bugzilla/show_bug.cgi?id=33236
Pull Request: https://github.com/llvm/llvm-project/pull/151639
This allows the contents of OVERLAYs to be attributed to memory regions.
This is the only clean way to overlap VMAs in linker scripts that choose
to primarily use memory regions to lay out addresses.
This also simplifies OVERLAY expansion to better match GNU LD.
Expressions for the first section's LMA and VMA are not generated if the
user did not provide them. This allows the LMA/VMA offset to be
preserved across multiple overlays in the same region, as with regular
sections.
Closes#129816
This prevents useless spills to the same memory region from causing
spilling to take too many passes to converge.
Handling this at spilling time allows us to relax the generation of
spill sections; specifically, multiple spills can now be generated per
output section. This should be fairly benign for performance, and it
would eventually allow linker scripts to express things like holes or
minimum addresses for parts of output sections. The linker could then
spill within an output section whenever address constraints are
violated.
According to the binutils spec:
https://sourceware.org/binutils/docs/ld/Input-Section-Basics.html
You should be able to specify all files in an archive using this syntax
`archivename:` , however, lld currently will only accept `archivename:*`
to match all files within an archive.
This patch will, only when necessary, create a copy of the file
specification and add an implicit wildcard `*` to the end. It also
updates the filename-spec linkerscript test to check for this behavior.
---------
Co-authored-by: Peter Smith <peter.smith@arm.com>
Store them in LinkerScript::descPool. This removes a SpecificAlloc
instantiation, makes lld smaller, and drops the small memory waste due
to the separate BumpPtrAllocator.
The inaccurate #111945 condition fixes a PROVIDE regression (#111478)
but introduces another regression: in a DSO link, if a symbol referenced
only by bitcode files is defined as PROVIDE_HIDDEN, lld would not set
the visibility correctly, leading to an assertion failure in
DynamicReloc::getSymIndex (https://reviews.llvm.org/D123985).
This is because `(sym->isUsedInRegularObj || sym->exportDynamic)` is
initially false (bitcode undef does not set `isUsedInRegularObj`) then
true (in `addSymbol`, after LTO compilation).
Fix this by making the condition accurate: use a map to track defined
symbols.
Reviewers: smithp35
Reviewed By: smithp35
Pull Request: https://github.com/llvm/llvm-project/pull/112386
Case: `PROVIDE(f1 = bar);` when both `f1` and `bar` are in separate
sections that would be discarded by GC.
Due to `demoteDefined`, `shouldAddProvideSym(f1)` may initially return
false (when Defined) and then return true (been demoted to Undefined).
```
addScriptReferencedSymbolsToSymTable
shouldAddProvideSym(f1): false
// the RHS (bar) is not added to `referencedSymbols` and may be GCed
declareSymbols
shouldAddProvideSym(f1): false
markLive
demoteSymbolsAndComputeIsPreemptible
// demoted f1 to Undefined
processSymbolAssignments
addSymbol
shouldAddProvideSym(f1): true
```
The inconsistency can cause `cmd->expression()` in `addSymbol` to be
evaluated, leading to `symbol not found: bar` errors (since `bar` in the
RHS is not in `referencedSymbols` and is GCed) (#111478).
Fix this by adding a `sym->isUsedInRegularObj` condition, making
`shouldAddProvideSym(f1)` values consistent. In addition, we need a
`sym->exportDynamic` condition to keep provide-shared.s working.
Fixes: ebb326a51fec37b5a47e5702e8ea157cd4f835cd
Pull Request: https://github.com/llvm/llvm-project/pull/111945
Since Ctx &ctx is a member variable,
1f391a75af8685e6bba89421443d72ac6a186599
7a5b9ef54eb96abd8415fd893576c42e51fd95db
e2f0ec3a3a8a2981be8a1aac2004cfb9064c61e8 can be reverted.
Remove the global variable `symtab` and add a member variable
(`std::unique_ptr<SymbolTable>`) to `Ctx` instead.
This is one step toward eliminating global states.
Pull Request: https://github.com/llvm/llvm-project/pull/109612
Ctx was introduced in March 2022 as a more suitable place for such
singletons.
llvm/Support/thread.h includes <thread>, which transitively includes
sstream in libc++ and uses ios_base::in, so we cannot use `#define in ctx.sec`.
`symtab, config, ctx` are now the only variables using
LLVM_LIBRARY_VISIBILITY.
Ctx was introduced in March 2022 as a more suitable place for such
singletons.
We now use default-initialization for `LinkerScript` and should pay
attention to non-class types (e.g. `dot` is initialized by commit
503907dc505db1e439e7061113bf84dd105f2e35).
RISC-V GCC with `-fdata-sections` will emit `.sbss.<name>`,
`.srodata.<name>`, and `.sdata.<name>` sections for small data items of
different kinds. Clang/LLVM already emits `.srodata.*` sections, and we
intend to emit the other two section name patterns in #87040.
This change ensures that any input sections starting `.sbss` are
combined into one output section called `.sbss`, and the same
respectively for `.srodata` and `.sdata`. This also allows the existing
RISC-V specific code for determining an output order for `.sbss` and
`.sdata` sections to apply to placing the sections.
This allows the input section matching algorithm to be separated from
output section descriptions. This allows a group of sections to be
assigned to multiple output sections, providing an explicit version of
--enable-non-contiguous-regions's spilling that doesn't require altering
global linker script matching behavior with a flag. It also makes the
linker script language more expressive even if spilling is not intended,
since input section matching can be done in a different order than
sections are placed in an output section.
The implementation reuses the backend mechanism provided by
--enable-non-contiguous-regions, so it has roughly similar semantics and
limitations. In particular, sections cannot be spilled into or out of
INSERT, OVERWRITE_SECTIONS, or /DISCARD/. The former two aren't
intrinsic, so it may be possible to relax those restrictions later.
Ctx was introduced in March 2022 as a more suitable place for such
singletons. ctx's hidden visibility optimizes generated instructions.
bufferStart and tlsPhdr, which are not OutputSection, can now be moved
outside of `Out`.
... using the temporary section type code 0x40000020
(`clang -c -Wa,--crel,--allow-experimental-crel`). LLVM will change the
code and break compatibility (Clang and lld of different versions are
not guaranteed to cooperate, unlike other features). CREL with implicit
addends are not supported.
---
Introduce `RelsOrRelas::crels` to iterate over SHT_CREL sections and
update users to check `crels`.
(The decoding performance is critical and error checking is difficult.
Follow `skipLeb` and `R_*LEB128` handling, do not use
`llvm::decodeULEB128`, whichs compiles to a lot of code.)
A few users (e.g. .eh_frame, LLDDwarfObj, s390x) require random access. Pass
`/*supportsCrel=*/false` to `relsOrRelas` to allocate a buffer and
convert CREL to RELA (`relas` instead of `crels` will be used). Since
allocating a buffer increases, the conversion is only performed when
absolutely necessary.
---
Non-alloc SHT_CREL sections may be created in -r and --emit-relocs
links. SHT_CREL and SHT_RELA components need reencoding since
r_offset/r_symidx/r_type/r_addend may change. (r_type may change because
relocations referencing a symbol in a discarded section are converted to
`R_*_NONE`).
* SHT_CREL components: decode with `RelsOrRelas` and re-encode (`OutputSection::finalizeNonAllocCrel`)
* SHT_RELA components: convert to CREL (`relToCrel`). An output section can only have one relocation section.
* SHT_REL components: print an error for now.
SHT_REL to SHT_CREL conversion for -r/--emit-relocs is complex and
unsupported yet.
Link: https://discourse.llvm.org/t/rfc-crel-a-compact-relocation-format-for-elf/77600
Pull Request: https://github.com/llvm/llvm-project/pull/98115
