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b94988cc08
This change was originally landed in: 5000a1b4b9edeb9e994f2a5b36da8d48599bea49
It was reverted in: 061e071d8c9b98526f35cad55a918a4f1615afd4
This change adds support for a new WASM_SEG_FLAG_STRINGS flag in
the object format which works in a similar fashion to SHF_STRINGS
in the ELF world.
Unlike the ELF linker this support is currently limited:
- No support for SHF_MERGE (non-string merging)
- Always do full tail merging ("lo" can be merged with "hello")
- Only support single byte strings (p2align 0)
Like the ELF linker merging is only performed at `-O1` and above.
This fixes part of https://bugs.llvm.org/show_bug.cgi?id=48828,
although crucially it doesn't not currently support debug sections
because they are not represented by data segments (they are custom
sections)
Differential Revision: https://reviews.llvm.org/D97657
95 lines
3.0 KiB
C++
95 lines
3.0 KiB
C++
//===- MCSectionWasm.h - Wasm Machine Code Sections -------------*- C++ -*-===//
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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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//
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// This file declares the MCSectionWasm class.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_MC_MCSECTIONWASM_H
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#define LLVM_MC_MCSECTIONWASM_H
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#include "llvm/MC/MCSection.h"
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namespace llvm {
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class MCSymbol;
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class MCSymbolWasm;
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class StringRef;
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class raw_ostream;
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/// This represents a section on wasm.
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class MCSectionWasm final : public MCSection {
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unsigned UniqueID;
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const MCSymbolWasm *Group;
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// The offset of the MC function/data section in the wasm code/data section.
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// For data relocations the offset is relative to start of the data payload
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// itself and does not include the size of the section header.
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uint64_t SectionOffset = 0;
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// For data sections, this is the index of of the corresponding wasm data
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// segment
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uint32_t SegmentIndex = 0;
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// For data sections, whether to use a passive segment
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bool IsPassive = false;
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// For data sections, bitfield of WasmSegmentFlag
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unsigned SegmentFlags;
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// The storage of Name is owned by MCContext's WasmUniquingMap.
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friend class MCContext;
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MCSectionWasm(StringRef Name, SectionKind K, unsigned SegmentFlags,
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const MCSymbolWasm *Group, unsigned UniqueID, MCSymbol *Begin)
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: MCSection(SV_Wasm, Name, K, Begin), UniqueID(UniqueID), Group(Group),
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SegmentFlags(SegmentFlags) {}
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public:
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/// Decides whether a '.section' directive should be printed before the
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/// section name
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bool shouldOmitSectionDirective(StringRef Name, const MCAsmInfo &MAI) const;
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const MCSymbolWasm *getGroup() const { return Group; }
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unsigned getSegmentFlags() const { return SegmentFlags; }
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void PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
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raw_ostream &OS,
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const MCExpr *Subsection) const override;
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bool UseCodeAlign() const override;
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bool isVirtualSection() const override;
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bool isWasmData() const {
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return Kind.isGlobalWriteableData() || Kind.isReadOnly() ||
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Kind.isThreadLocal();
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}
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bool isUnique() const { return UniqueID != ~0U; }
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unsigned getUniqueID() const { return UniqueID; }
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uint64_t getSectionOffset() const { return SectionOffset; }
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void setSectionOffset(uint64_t Offset) { SectionOffset = Offset; }
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uint32_t getSegmentIndex() const { return SegmentIndex; }
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void setSegmentIndex(uint32_t Index) { SegmentIndex = Index; }
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bool getPassive() const {
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assert(isWasmData());
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return IsPassive;
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}
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void setPassive(bool V = true) {
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assert(isWasmData());
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IsPassive = V;
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}
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static bool classof(const MCSection *S) { return S->getVariant() == SV_Wasm; }
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};
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} // end namespace llvm
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#endif
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