Instead of caching STI in the RISCVELFTargetStreamer, store the two
flags we need from it.
My goal is to allow RISCVAsmPrinter to override these flags using IR
module metadata for LTO. So they need to be separated from the STI used
to construct the TargetStreamer.
This patch should be NFC as long as no one is changing the contents of
the STI that was used to construct the TargetStreamer between the
constructor and the use of the flags.
Regarding
```
.option norelax
j label
.option relax
// relaxable instructions
// For assembly input, RISCVAsmParser::ParseInstruction will set ForceRelocs (https://reviews.llvm.org/D46423).
// For direct object emission, ForceRelocs is not set after https://github.com/llvm/llvm-project/pull/73721
label:
```
The J instruction needs a relocation to ensure the target is correct
after linker relaxation. This is related a limitation in the assembler:
RISCVAsmBackend::shouldForceRelocation decides upfront whether a
relocation is needed, instead of checking more information (whether
there are relaxable fragments in between).
Despite the limitation, `j label` produces a relocation in direct object
emission mode, but was broken by #73721 due to the shouldForceRelocation
limitation.
Add a workaround to RISCVTargetELFStreamer to emulate the previous
behavior.
Link: https://github.com/ClangBuiltLinux/linux/issues/1965
Mapping symbols [1] are special ELF symbols that can be inserted to
indicate regions of code or data. A sequence of data bytes is indicated
by a `$d` (or `$d.<any>`) symbol pointing to its start while a sequence
of instructions uses a `$x` (or `$x.<any>`) symbol. This can be used,
for example, to assist disassembling a memory region containing both
data and code.
This patch implements mapping symbols for RISC-V, copying the
implementation mostly from the AArch64 target.
Note that the `$x<ISA>` mapping symbol, indicating an instruction
sequence with a specific ISA extension, is not implemented by this
patch. As far as I can tell, binutils doesn't implement this yet either.
Note that this patch uses the same symbol naming convention as the
AArch64 target: always use `$x.i` and `$d.i` (where `i` is a
monotonically increasing counter). This differs from binutils where all
symbols are named `$x` or `$d` (causing multiple symbol having the same
name). I'm not not sure whether it makes more sense to avoid duplicate
symbol names or be consistent with binutils.
Note that the handling of nop-slides inserted for alignment differs from
binutils: binutils always marks the nops as instructions (`$x`) while
this patch doesn't insert a symbol for the nops (so the last inserted
symbol is used). I believe binutil's behavior makes most sense but this
seems difficult to implement in LLVM as the insertion of nops is handled
by `RISCVAsmBackend`. At this point, inserting ELF symbols seems
impossible. Any ideas for how to handle this would be appreciated.
[1]: https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/master/riscv-elf.adoc#mapping-symbol
Depends on D156190 and D156236
Differential Revision: https://reviews.llvm.org/D153260
For a label difference `A-B` in assembly, if A and B are separated by a
linker-relaxable instruction, we should emit a pair of ADD/SUB
relocations (e.g. R_RISCV_ADD32/R_RISCV_SUB32,
R_RISCV_ADD64/R_RISCV_SUB64).
However, the decision is made upfront at parsing time with inadequate
heuristics (`requiresFixup`). As a result, LLVM integrated assembler
incorrectly suppresses R_RISCV_ADD32/R_RISCV_SUB32 for the following
code:
```
// Simplified from a workaround https://android-review.googlesource.com/c/platform/art/+/2619609
// Both end and begin are not defined yet. We decide ADD/SUB relocations upfront and don't know they will be needed.
.4byte end-begin
begin:
call foo
end:
```
To fix the bug, make two primary changes:
* Delete `requiresFixups` and the overridden emitValueImpl (from D103539).
This deletion requires accurate evaluateAsAbolute (D153097).
* In MCAssembler::evaluateFixup, call handleAddSubRelocations to emit
ADD/SUB relocations.
However, there is a remaining issue in
MCExpr.cpp:AttemptToFoldSymbolOffsetDifference. With MCAsmLayout, we may
incorrectly fold A-B even when A and B are separated by a
linker-relaxable instruction. This deficiency is acknowledged (see
D153097), but was previously bypassed by eagerly emitting ADD/SUB using
`requiresFixups`. To address this, we partially reintroduce `canFold` (from
D61584, removed by D103539).
Some expressions (e.g. .size and .fill) need to take the `MCAsmLayout`
code path in AttemptToFoldSymbolOffsetDifference, avoiding relocations
(weird, but matching GNU assembler and needed to match user
expectation). Switch to evaluateKnownAbsolute to leverage the `InSet`
condition.
As a bonus, this change allows for the removal of some relocations for
the FDE `address_range` field in the .eh_frame section.
riscv64-64b-pcrel.s contains the main test.
Add a linker relaxable instruction to dwarf-riscv-relocs.ll to test what
it intends to test.
Merge fixups-relax-diff.ll into fixups-diff.ll.
Reviewed By: kito-cheng
Differential Revision: https://reviews.llvm.org/D155357
D132262 tried to simplify `IsMetadataOrEHFrameSection` originally introduced in
D127549 but caused a regression as `.quad` directives in
```
.section .note,"a",@note; note:
.quad extern-note # extern is undefined
.section .rodata,"a",@progbits; rodata:
.quad extern-rodata # extern is undefined
.section .nonalloc,"",@progbits; nw:
.quad extern-nw
```
are incorrectly rejected: these differences may be link-time constants and
are allowed in GNU assembler and LLVM MC's non-RISC-V ports.
Relax the conditions to allow these cases. For A-B, A may be defined later, but
this requiresFixups call has to eagerly make a decision. For now, emit ADD/SUB
unless A is `.L*`. This euristic handles many temporary label differences for
.debug_* and .apple_types sections. Ideally we should delay the decision of
PC-relative vs ADD/SUB until A is defined.
Reviewed By: compnerd
Differential Revision: https://reviews.llvm.org/D145474
Follow-up to D143226
Currently we incorrectly emit R_RISCV_ADD32/R_RISCV_SUB32.
Emit R_RISCV_PLT32 instead. The new behavior matches x86-64 and AArch64.
D102894 introduced common code for the emission of ELF attributes. Our
implementation in RISC-V predates this, and basically copies the Arm
logic at the time. This patch removes that duplication and uses the
shared logic instead.
Differential Revision: https://reviews.llvm.org/D145570
Reuse it for RISCVAsmBackend.cpp.
While there make the function return a pair of MCFixupKind to
remove static_casts elsewhere.
Reviewed By: reames
Differential Revision: https://reviews.llvm.org/D142955
Move the declaration of RISCVELFStreamer from RISCVELFStreamer.cpp to RISCVELFStreamer.h.
Change the return type of getStreamer() to support the use of overloading and other functions in RISCVELFStreamer.
Differential Revision: https://reviews.llvm.org/D138500
The patch is split from D103435. The patch supported a new directive .variant_cc
that annotates function with STO_RISCV_VARIANT_CC. Symbols marked with
STO_RISCV_VARIANT_CC do not use standard calling conversion or use parameter not
passed in GPR/FPR.
Related: https://github.com/riscv/riscv-elf-psabi-doc/pull/190
Initial authored by: HsiangKai
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D138352
Simplify and make the pair-wise relocation more precise. If either of
the symbol references are textual, the relocation must be delayed. If
the difference is across sections, delay it as well which partially
matches the behaviour of gas. We unfortunately do not handle the case
where the difference references a symbol that is not yet defined. In
such a case, we simply fail to resolve the difference, which should
hopefully not be too onerous (particularly since no other target
supports cross-section references and it is not clear if this was
intentional on the part of RISCV).
Differential Revision: https://reviews.llvm.org/D132262
Reviewed By: @MaskRay
This is a minimalist implementation which simply adds the extension (in the experimental namespace since its not ratified), and wires up the setting of the required ELF header flag. Future changes will include codegen changes to exploit the stronger memory model.
This is intended to implement v0.1 of the proposed specification which can be found in Chapter 25 of https://github.com/riscv/riscv-isa-manual/releases/download/draft-20220723-10eea63/riscv-spec.pdf.
Differential Revision: https://reviews.llvm.org/D133239
This fixes test/DebugInfo/Generic/accel-table-hash-collisions.ll and
cross-cu-inlining.ll when the default triple is riscv. llvm-dwarfdump
--apple-names does not resolve R_RISCV_{ADD,SUB}32 in .apple_names .apple_types
and having ADD/SUB will cause decoding failure `Atom[0]: Error extracting the
value`.
We would previously fail to handle 64-bit PC-relative relocations on
RISCV. This was exposed by trying to build with
`-fprofile-instr-generate`.
The original changes restricted the relocation handling to the text
segment as the paired relocations are undesirable in at least the debug
and .eh_frame sections. We now make this explicit to handle the general
case for the data relocations as well.
It would be preferable to use `R_RISCV_n_PCREL` when available to avoid
an extra relocation.
Differential Revision: https://reviews.llvm.org/D127549
Reviewed By: luismarques, MaskRay
Fixes: #55971
We didn't implement RISCVELFStreamer::reset and cause some very strange
section output for attribute section...just reference D15950 to see how
ARM implement that.
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D125905
In the past, when construct RISCVAsmBackend, MCTargetOptions.ABIName would be passed and stored in RISCVAsmBackend.
But MCTargetOptions.ABIName can only be specified by -target-abi xxx in command line, if the .ll file has target-abi attribute, the codegen module will ignore it. And the generated object file would have incorrect EFlags value.
https://github.com/llvm/llvm-project/issues/50591 also caused by this problem.
This patch override the AsmPrinter::emitFunctionEntryLabel function and use it to set the target abi value that get from .ll file's target-abi attribute. And storing the target-abi in RISCVTargetStreamer instead of RISCVAsmBackend.
Differential Revision: https://reviews.llvm.org/D121183
There's a few relevant forward declarations in there that may require downstream
adding explicit includes:
llvm/MC/MCContext.h no longer includes llvm/BinaryFormat/ELF.h, llvm/MC/MCSubtargetInfo.h, llvm/MC/MCTargetOptions.h
llvm/MC/MCObjectStreamer.h no longer include llvm/MC/MCAssembler.h
llvm/MC/MCAssembler.h no longer includes llvm/MC/MCFixup.h, llvm/MC/MCFragment.h
Counting preprocessed lines required to rebuild llvm-project on my setup:
before: 1052436830
after: 1049293745
Which is significant and backs up the change in addition to the usual benefits of
decreasing coupling between headers and compilation units.
Discourse thread: https://discourse.llvm.org/t/include-what-you-use-include-cleanup
Differential Revision: https://reviews.llvm.org/D119244
This re-architects the RISCV relocation handling to bring the
implementation closer in line with the implementation in binutils. We
would previously aggressively resolve the relocation. With this
restructuring, we always will emit a paired relocation for any symbolic
difference of the type of S±T[±C] where S and T are labels and C is a
constant.
GAS has a special target hook controlled by `RELOC_EXPANSION_POSSIBLE`
which indicates that a fixup may be expanded into multiple relocations.
This is used by the RISCV backend to always emit a paired relocation -
either ADD[WIDTH] + SUB[WIDTH] for text relocations or SET[WIDTH] +
SUB[WIDTH] for a debug info relocation. Irrespective of whether linker
relaxation support is enabled, symbolic difference is always emitted as
a paired relocation.
This change also sinks the target specific behaviour down into the
target specific area rather than exposing it to the shared relocation
handling. In the process, we also sink the "special" handling for debug
information down into the RISCV target. Although this improves the path
for the other targets, this is not necessarily entirely ideal either.
The changes in the debug info emission could be done through another
type of hook as this functionality would be required by any other target
which wishes to do linker relaxation. However, as there are no other
targets in LLVM which currently do this, this is a reasonable thing to
do until such time as the code needs to be shared.
Improve the handling of the relocation (and add a reduced test case from
the Linux kernel) to ensure that we handle complex expressions for
symbolic difference. This ensures that we correct relocate symbols with
the adddends normalized and associated with the addition portion of the
paired relocation.
This change also addresses some review comments from Alex Bradbury about
the relocations meant for use in the DWARF CFA being named incorrectly
(using ADD6 instead of SET6) in the original change which introduced the
relocation type.
This resolves the issues with the symbolic difference emission
sufficiently to enable building the Linux kernel with clang+IAS+lld
(without linker relaxation).
Resolves PR50153, PR50156!
Fixes: ClangBuiltLinux/linux#1023, ClangBuiltLinux/linux#1143
Reviewed By: nickdesaulniers, maskray
Differential Revision: https://reviews.llvm.org/D103539
MCTargetDesc includes headers from Utils and Utils includes headers
from MCTargetDesc. So from a library layering perspective it makes sense
for them to be in the same library. I guess the other option might be to
move the tablegen includes from RISCVMCTargetDesc.h to RISCVBaseInfo.h
so that RISCVBaseInfo.h didn't need to include RISCVMCTargetDesc.h.
Everything else that depends on Utils also depends on MCTargetDesc so
having one library seemed simpler.
Differential Revision: https://reviews.llvm.org/D93168
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
This patch adds proper handling of -target-abi, as accepted by llvm-mc and
llc. Lowering (codegen) for the hard-float ABIs will follow in a subsequent
patch. However, this patch does add MC layer support for the hard float and
RVE ABIs (emission of the appropriate ELF flags
https://github.com/riscv/riscv-elf-psabi-doc/blob/master/riscv-elf.md#-file-header).
ABI parsing must be shared between codegen and the MC layer, so we add
computeTargetABI to RISCVUtils. A warning will be printed if an invalid or
unrecognized ABI is given.
Differential Revision: https://reviews.llvm.org/D59023
llvm-svn: 355771
to reflect the new license.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351636
This adds support in the RISCVAsmParser the storing of Subtarget feature bits to a stack so that they can be pushed/popped to enable/disable multiple features at once.
Differential Revision: https://reviews.llvm.org/D46424
Patch by Lewis Revill.
llvm-svn: 347774
This extends the .option support from D45864 to enable/disable the relax
feature flag from D44886
During parsing of the relax/norelax directives, the RISCV::FeatureRelax
feature bits of the SubtargetInfo stored in the AsmParser are updated
appropriately to reflect whether relaxation is currently enabled in the
parser. When an instruction is parsed, the parser checks if relaxation is
currently enabled and if so, gets a handle to the AsmBackend and sets the
ForceRelocs flag. The AsmBackend uses a combination of the original
RISCV::FeatureRelax feature bits set by e.g -mattr=+/-relax and the
ForceRelocs flag to determine whether to emit relocations for symbol and
branch diffs. Diff relocations should therefore only not be emitted if the
relax flag was not set on the command line and no instruction was ever parsed
in a section with relaxation enabled to ensure correct diffs are emitted.
Differential Revision: https://reviews.llvm.org/D46423
Patch by Lewis Revill.
llvm-svn: 346655
These directives allow the 'C' (compressed) extension to be enabled/disabled
within a single file.
Differential Revision: https://reviews.llvm.org/D45864
Patch by Kito Cheng
llvm-svn: 332107
