Commit 95fa5c4f authored by Shengchen Kan's avatar Shengchen Kan
Browse files

[X86] Move the function getOrCreateBoundaryAlignFragment 

MCObjectStreamer is more suitable to create fragments than
X86AsmBackend, for example, the function getOrCreateDataFragment is
defined in MCObjectStreamer.

Differential Revision: https://reviews.llvm.org/D75351
parent 129a7625

llvm/include/llvm/MC/MCFragment.h

+2 −1
Original line number Diff line number Diff line
@@ -533,7 +533,7 @@ class MCBoundaryAlignFragment : public MCFragment { 
  uint64_t Size = 0;



public:

  MCBoundaryAlignFragment(Align AlignBoundary, bool Fused = false,

  MCBoundaryAlignFragment(Align AlignBoundary = Align(1), bool Fused = false,

                          bool EmitNops = false, MCSection *Sec = nullptr)

      : MCFragment(FT_BoundaryAlign, false, Sec), AlignBoundary(AlignBoundary),

        Fused(Fused), EmitNops(EmitNops) {}
@@ -542,6 +542,7 @@ public: 
  void setSize(uint64_t Value) { Size = Value; }



  Align getAlignment() const { return AlignBoundary; }

  void setAlignment(Align Value) { AlignBoundary = Value; }



  bool isFused() const { return Fused; }

  void setFused(bool Value) { Fused = Value; }

llvm/include/llvm/MC/MCObjectStreamer.h

+5 −0
Original line number Diff line number Diff line
@@ -87,6 +87,11 @@ public: 
  /// if the Subtarget differs from the current fragment.

  MCDataFragment *getOrCreateDataFragment(const MCSubtargetInfo* STI = nullptr);



  /// Get a boundary-align fragment to write into, creating a new one if the

  /// current fragment is not a boundary-align fragment or has been used to emit

  /// something.

  MCBoundaryAlignFragment *getOrCreateBoundaryAlignFragment();



protected:

  bool changeSectionImpl(MCSection *Section, const MCExpr *Subsection);

llvm/lib/MC/MCObjectStreamer.cpp

+9 −0
Original line number Diff line number Diff line
@@ -215,6 +215,15 @@ MCObjectStreamer::getOrCreateDataFragment(const MCSubtargetInfo *STI) { 
  return F;

}



MCBoundaryAlignFragment *MCObjectStreamer::getOrCreateBoundaryAlignFragment() {

  auto *F = dyn_cast_or_null<MCBoundaryAlignFragment>(getCurrentFragment());

  if (!F || F->canEmitNops()) {

    F = new MCBoundaryAlignFragment();

    insert(F);

  }

  return F;

}



void MCObjectStreamer::visitUsedSymbol(const MCSymbol &Sym) {

  Assembler->registerSymbol(Sym);

}

llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp

+4 −19
Original line number Diff line number Diff line
@@ -120,8 +120,6 @@ class X86AsmBackend : public MCAsmBackend { 


  bool needAlign(MCObjectStreamer &OS) const;

  bool needAlignInst(const MCInst &Inst) const;

  MCBoundaryAlignFragment *

  getOrCreateBoundaryAlignFragment(MCObjectStreamer &OS) const;

  MCInst PrevInst;



public:
@@ -395,21 +393,6 @@ bool X86AsmBackend::needAlignInst(const MCInst &Inst) const { 
          (AlignBranchType & X86::AlignBranchIndirect));

}



static bool canReuseBoundaryAlignFragment(const MCBoundaryAlignFragment &F) {

  // If a MCBoundaryAlignFragment has not been used to emit NOP,we can reuse it.

  return !F.canEmitNops();

}



MCBoundaryAlignFragment *

X86AsmBackend::getOrCreateBoundaryAlignFragment(MCObjectStreamer &OS) const {

  auto *F = dyn_cast_or_null<MCBoundaryAlignFragment>(OS.getCurrentFragment());

  if (!F || !canReuseBoundaryAlignFragment(*F)) {

    F = new MCBoundaryAlignFragment(AlignBoundary);

    OS.insert(F);

  }

  return F;

}



/// Insert MCBoundaryAlignFragment before instructions to align branches.

void X86AsmBackend::alignBranchesBegin(MCObjectStreamer &OS,

                                       const MCInst &Inst) {
@@ -439,13 +422,15 @@ void X86AsmBackend::alignBranchesBegin(MCObjectStreamer &OS, 
    //

    // We will treat the JCC as a unfused branch although it may be fused

    // with the CMP.

    auto *F = getOrCreateBoundaryAlignFragment(OS);

    auto *F = OS.getOrCreateBoundaryAlignFragment();

    F->setAlignment(AlignBoundary);

    F->setEmitNops(true);

    F->setFused(false);

  } else if (NeedAlignFused && isFirstMacroFusibleInst(Inst, *MCII)) {

    // We don't know if macro fusion happens until the reaching the next

    // instruction, so a place holder is put here if necessary.

    getOrCreateBoundaryAlignFragment(OS);

    auto *F = OS.getOrCreateBoundaryAlignFragment();

    F->setAlignment(AlignBoundary);

  }



  PrevInst = Inst;