dc3a4c0fcf
Refactor the fragment representation of `push rax; jmp foo; nop; jmp foo`, previously encoded as `MCDataFragment(nop); MCRelaxableFragment(jmp foo); MCDataFragment(nop); MCRelaxableFragment(jmp foo)`, to ``` MCFragment(fixed: push rax, variable: jmp foo) MCFragment(fixed: nop, variable: jmp foo) ``` Changes: * Eliminate MCEncodedFragment, moving content and fixup storage to MCFragment. * The new MCFragment contains a fixed-size content (similar to previous MCDataFragment) and an optional variable-size tail. * The variable-size tail supports FT_Relaxable, FT_LEB, FT_Dwarf, and FT_DwarfFrame, with plans to extend to other fragment types. dyn_cast/isa should be avoided for the converted fragment subclasses. * In `setVarFixups`, source fixup offsets are relative to the variable part's start. Stored fixup (in `FixupStorage`) offsets are relative to the fixed part's start. A lot of code does `getFragmentOffset(Frag) + Fixup.getOffset()`, expecting the fixup offset to be relative to the fixed part's start. * HexagonAsmBackend::fixupNeedsRelaxationAdvanced needs to know the associated instruction for a fixup. We have to add a `const MCFragment &` parameter. * In MCObjectStreamer, extend `absoluteSymbolDiff` to apply to FT_Relaxable as otherwise there would be many more FT_DwarfFrame fragments in -g compilations. https://llvm-compile-time-tracker.com/compare.php?from=28e1473e8e523150914e8c7ea50b44fb0d2a8d65&to=778d68ad1d48e7f111ea853dd249912c601bee89&stat=instructions:u ``` stage2-O0-g instructins:u geomeon (-0.07%) stage1-ReleaseLTO-g (link only) max-rss geomean (-0.39%) ``` ``` % /t/clang-old -g -c sqlite3.i -w -mllvm -debug-only=mc-dump &| awk '/^[0-9]+/{s[$2]++;tot++} END{print "Total",tot; n=asorti(s, si); for(i=1;i<=n;i++) print si[i],s[si[i]]}' Total 59675 Align 2215 Data 29700 Dwarf 12044 DwarfCallFrame 4216 Fill 92 LEB 12 Relaxable 11396 % /t/clang-new -g -c sqlite3.i -w -mllvm -debug-only=mc-dump &| awk '/^[0-9]+/{s[$2]++;tot++} END{print "Total",tot; n=asorti(s, si); for(i=1;i<=n;i++) print si[i],s[si[i]]}' Total 32287 Align 2215 Data 2312 Dwarf 12044 DwarfCallFrame 4216 Fill 92 LEB 12 Relaxable 11396 ``` Pull Request: https://github.com/llvm/llvm-project/pull/148544
88 lines
2.9 KiB
C++
88 lines
2.9 KiB
C++
//===- lib/MC/MCSymbol.cpp - MCSymbol implementation ----------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/MC/MCSymbol.h"
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#include "llvm/ADT/StringRef.h"
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#include "llvm/Config/llvm-config.h"
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#include "llvm/MC/MCAsmInfo.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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#include <cassert>
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#include <cstddef>
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using namespace llvm;
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// Only the address of this fragment is ever actually used.
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static MCFragment SentinelFragment;
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// Sentinel value for the absolute pseudo fragment.
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MCFragment *MCSymbol::AbsolutePseudoFragment = &SentinelFragment;
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void *MCSymbol::operator new(size_t s, const MCSymbolTableEntry *Name,
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MCContext &Ctx) {
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// We may need more space for a Name to account for alignment. So allocate
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// space for the storage type and not the name pointer.
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size_t Size = s + (Name ? sizeof(NameEntryStorageTy) : 0);
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// For safety, ensure that the alignment of a pointer is enough for an
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// MCSymbol. This also ensures we don't need padding between the name and
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// symbol.
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static_assert((unsigned)alignof(MCSymbol) <= alignof(NameEntryStorageTy),
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"Bad alignment of MCSymbol");
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void *Storage = Ctx.allocate(Size, alignof(NameEntryStorageTy));
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NameEntryStorageTy *Start = static_cast<NameEntryStorageTy*>(Storage);
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NameEntryStorageTy *End = Start + (Name ? 1 : 0);
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return End;
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}
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void MCSymbol::setVariableValue(const MCExpr *Value) {
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assert(Value && "Invalid variable value!");
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assert((SymbolContents == SymContentsUnset ||
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SymbolContents == SymContentsVariable) &&
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"Cannot give common/offset symbol a variable value");
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this->Value = Value;
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SymbolContents = SymContentsVariable;
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setUndefined();
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}
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void MCSymbol::print(raw_ostream &OS, const MCAsmInfo *MAI) const {
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// The name for this MCSymbol is required to be a valid target name. However,
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// some targets support quoting names with funny characters. If the name
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// contains a funny character, then print it quoted.
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StringRef Name = getName();
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if (!MAI || MAI->isValidUnquotedName(Name)) {
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OS << Name;
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return;
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}
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if (MAI && !MAI->supportsNameQuoting())
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report_fatal_error("Symbol name with unsupported characters");
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OS << '"';
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for (char C : Name) {
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if (C == '\n')
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OS << "\\n";
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else if (C == '"')
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OS << "\\\"";
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else if (C == '\\')
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OS << "\\\\";
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else
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OS << C;
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}
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OS << '"';
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}
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#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
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LLVM_DUMP_METHOD void MCSymbol::dump() const {
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dbgs() << *this;
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}
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#endif
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