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fb13e8ff55
Summary: This fixes a dumpbin warning on objects produced by the MC assembler when starting from text. All .debug$S sections are supposed to be marked IMAGE_SCN_MEM_DISCARDABLE. The main, non-COMDAT .debug$S section had this set, but any comdat ones were not being marked discardable because there was no .section flag for it. This change does two things: - If the section name starts with .debug, implicitly mark the section as discardable. This means we do the same thing as gas on .s files with DWARF from GCC, which is important. - Adds the 'D' flag to the .section directive on COFF to explicitly say a section is discardable. We only emit this flag if the section name does not start with .debug. This allows the user to explicitly tweak their section flags without worrying about magic section names. The only thing you can't do in this scheme is to create a non-discardable section with a name starting with ".debug", but hopefully users don't need that. Reviewers: majnemer, rafael Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D24582 llvm-svn: 281554
97 lines
3.3 KiB
C++
97 lines
3.3 KiB
C++
//===- MCSectionCOFF.h - COFF Machine Code Sections -------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file declares the MCSectionCOFF class.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_MC_MCSECTIONCOFF_H
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#define LLVM_MC_MCSECTIONCOFF_H
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#include "llvm/ADT/StringRef.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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/// This represents a section on Windows
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class MCSectionCOFF final : public MCSection {
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// The memory for this string is stored in the same MCContext as *this.
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StringRef SectionName;
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// FIXME: The following fields should not be mutable, but are for now so the
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// asm parser can honor the .linkonce directive.
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/// This is the Characteristics field of a section, drawn from the enums
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/// below.
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mutable unsigned Characteristics;
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/// The unique IDs used with the .pdata and .xdata sections created internally
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/// by the assembler. This ID is used to ensure that for every .text section,
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/// there is exactly one .pdata and one .xdata section, which is required by
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/// the Microsoft incremental linker. This data is mutable because this ID is
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/// not notionally part of the section.
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mutable unsigned WinCFISectionID = ~0U;
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/// The COMDAT symbol of this section. Only valid if this is a COMDAT section.
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/// Two COMDAT sections are merged if they have the same COMDAT symbol.
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MCSymbol *COMDATSymbol;
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/// This is the Selection field for the section symbol, if it is a COMDAT
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/// section (Characteristics & IMAGE_SCN_LNK_COMDAT) != 0
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mutable int Selection;
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private:
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friend class MCContext;
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MCSectionCOFF(StringRef Section, unsigned Characteristics,
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MCSymbol *COMDATSymbol, int Selection, SectionKind K,
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MCSymbol *Begin)
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: MCSection(SV_COFF, K, Begin), SectionName(Section),
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Characteristics(Characteristics), COMDATSymbol(COMDATSymbol),
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Selection(Selection) {
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assert((Characteristics & 0x00F00000) == 0 &&
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"alignment must not be set upon section creation");
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}
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public:
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~MCSectionCOFF();
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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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StringRef getSectionName() const { return SectionName; }
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unsigned getCharacteristics() const { return Characteristics; }
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MCSymbol *getCOMDATSymbol() const { return COMDATSymbol; }
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int getSelection() const { return Selection; }
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void setSelection(int Selection) const;
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void PrintSwitchToSection(const MCAsmInfo &MAI, 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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unsigned getOrAssignWinCFISectionID(unsigned *NextID) const {
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if (WinCFISectionID == ~0U)
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WinCFISectionID = (*NextID)++;
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return WinCFISectionID;
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}
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static bool isImplicitlyDiscardable(StringRef Name) {
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return Name.startswith(".debug");
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}
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static bool classof(const MCSection *S) { return S->getVariant() == SV_COFF; }
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};
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} // end namespace llvm
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#endif
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