3769ce013b
Each section now tracks the index of the first linker-relaxable fragment, enabling two changes: * Delete redundant ALIGN relocations before the first linker-relaxable instruction in a section. The primary example is the offset 0 R_RISCV_ALIGN relocation for a text section aligned by 4. * For alignments larger than the NOP size after the first linker-relaxable instruction, ALIGN relocations are now generated, even in norelax regions. This fixes the issue #150159. The new test llvm/test/MC/RISCV/Relocations/align-after-relax.s verifies the required ALIGN in a norelax region following linker-relaxable instructions. By using a fragment index within the subsection (which is less than or equal to the section's index), the implementation may generate redundant ALIGN relocations in lower-numbered subsections before the first linker-relaxable instruction. align-option-relax.s demonstrates the ALIGN optimization. Add an initial `call` to a few tests to prevent the ALIGN optimization. --- When the alignment exceeds 2, we insert $alignment-2 bytes of NOPs, even in non-RVC code. This enables non-RVC code following RVC code to handle a 2-byte adjustment without requiring an additional state in MCSection or AsmParser. ``` .globl _start _start: // GNU ld can relax this to 6505 lui a0, 0x1 // LLD hasn't implemented this transformation. lui a0, %hi(foo) .option push .option norelax .option norvc // Now we generate R_RISCV_ALIGN with addend 2, even if this is a norvc region. .balign 4 b0: .word 0x3a393837 .option pop foo: ``` Pull Request: https://github.com/llvm/llvm-project/pull/150816
102 lines
3.3 KiB
C++
102 lines
3.3 KiB
C++
//===- lib/MC/MCSection.cpp - Machine Code Section Representation ---------===//
|
|
//
|
|
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
|
|
// See https://llvm.org/LICENSE.txt for license information.
|
|
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/MC/MCSection.h"
|
|
#include "llvm/ADT/SmallVector.h"
|
|
#include "llvm/Config/llvm-config.h"
|
|
#include "llvm/MC/MCContext.h"
|
|
#include "llvm/MC/MCSymbol.h"
|
|
#include "llvm/Support/Compiler.h"
|
|
#include "llvm/Support/ErrorHandling.h"
|
|
#include "llvm/Support/raw_ostream.h"
|
|
#include <utility>
|
|
|
|
using namespace llvm;
|
|
|
|
MCSection::MCSection(StringRef Name, bool IsText, bool IsBss, MCSymbol *Begin)
|
|
: Begin(Begin), HasInstructions(false), IsRegistered(false), IsText(IsText),
|
|
IsBss(IsBss), Name(Name) {
|
|
DummyFragment.setParent(this);
|
|
}
|
|
|
|
MCSymbol *MCSection::getEndSymbol(MCContext &Ctx) {
|
|
if (!End)
|
|
End = Ctx.createTempSymbol("sec_end");
|
|
return End;
|
|
}
|
|
|
|
bool MCSection::hasEnded() const { return End && End->isInSection(); }
|
|
|
|
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
|
|
LLVM_DUMP_METHOD void MCSection::dump(
|
|
DenseMap<const MCFragment *, SmallVector<const MCSymbol *, 0>> *FragToSyms)
|
|
const {
|
|
raw_ostream &OS = errs();
|
|
|
|
OS << "MCSection Name:" << getName();
|
|
for (auto &F : *this) {
|
|
OS << '\n';
|
|
F.dump();
|
|
if (!FragToSyms)
|
|
continue;
|
|
auto It = FragToSyms->find(&F);
|
|
if (It == FragToSyms->end())
|
|
continue;
|
|
for (auto *Sym : It->second) {
|
|
OS << "\n Symbol @" << Sym->getOffset() << ' ' << Sym->getName();
|
|
if (Sym->isTemporary())
|
|
OS << " Temporary";
|
|
}
|
|
}
|
|
}
|
|
#endif
|
|
|
|
void MCFragment::setVarContents(ArrayRef<char> Contents) {
|
|
auto &S = getParent()->ContentStorage;
|
|
if (VarContentStart + Contents.size() > VarContentEnd) {
|
|
VarContentStart = S.size();
|
|
S.resize_for_overwrite(S.size() + Contents.size());
|
|
}
|
|
VarContentEnd = VarContentStart + Contents.size();
|
|
llvm::copy(Contents, S.begin() + VarContentStart);
|
|
}
|
|
|
|
void MCFragment::addFixup(MCFixup Fixup) { appendFixups({Fixup}); }
|
|
|
|
void MCFragment::appendFixups(ArrayRef<MCFixup> Fixups) {
|
|
auto &S = getParent()->FixupStorage;
|
|
if (LLVM_UNLIKELY(FixupEnd != S.size())) {
|
|
// Move the elements to the end. Reserve space to avoid invalidating
|
|
// S.begin()+I for `append`.
|
|
auto Size = FixupEnd - FixupStart;
|
|
auto I = std::exchange(FixupStart, S.size());
|
|
S.reserve(S.size() + Size);
|
|
S.append(S.begin() + I, S.begin() + I + Size);
|
|
}
|
|
S.append(Fixups.begin(), Fixups.end());
|
|
FixupEnd = S.size();
|
|
}
|
|
|
|
void MCFragment::setVarFixups(ArrayRef<MCFixup> Fixups) {
|
|
assert(Fixups.size() < 256 &&
|
|
"variable-size tail cannot have more than 256 fixups");
|
|
auto &S = getParent()->FixupStorage;
|
|
if (Fixups.size() > VarFixupSize) {
|
|
VarFixupStart = S.size();
|
|
S.resize_for_overwrite(S.size() + Fixups.size());
|
|
}
|
|
VarFixupSize = Fixups.size();
|
|
// Source fixup offsets are relative to the variable part's start. Add the
|
|
// fixed part size to make them relative to the fixed part's start.
|
|
std::transform(Fixups.begin(), Fixups.end(), S.begin() + VarFixupStart,
|
|
[Fixed = getFixedSize()](MCFixup F) {
|
|
F.setOffset(Fixed + F.getOffset());
|
|
return F;
|
|
});
|
|
}
|