llvm · MaskRay · Jul 20, 2025 · Jul 20, 2025 · Jul 20, 2025
diff --git a/llvm/include/llvm/MC/MCObjectStreamer.h b/llvm/include/llvm/MC/MCObjectStreamer.h
@@ -72,9 +72,6 @@ class MCObjectStreamer : public MCStreamer {
   MCSymbol *emitCFILabel() override;
   void emitCFISections(bool EH, bool Debug) override;
 
-  // TODO: Change callers to use getCurrentFragment instead.
-  MCFragment *getOrCreateDataFragment() { return getCurrentFragment(); }
-
 protected:
   bool changeSectionImpl(MCSection *Section, uint32_t Subsection);
 

diff --git a/llvm/include/llvm/MC/MCSection.h b/llvm/include/llvm/MC/MCSection.h
@@ -179,8 +179,6 @@ class LLVM_ABI MCSection {
   /// Check whether this section is "virtual", that is has no actual object
   /// file contents.
   bool isVirtualSection() const { return IsVirtual; }
-
-  virtual StringRef getVirtualSectionKind() const;
 };
 
 // Represents a contiguous piece of code or data within a section. Its size is

diff --git a/llvm/include/llvm/MC/MCSectionCOFF.h b/llvm/include/llvm/MC/MCSectionCOFF.h
@@ -82,7 +82,6 @@ class MCSectionCOFF final : public MCSection {
                             raw_ostream &OS,
                             uint32_t Subsection) const override;
   bool useCodeAlign() const override;
-  StringRef getVirtualSectionKind() const override;
 
   unsigned getOrAssignWinCFISectionID(unsigned *NextID) const {
     if (WinCFISectionID == ~0U)

diff --git a/llvm/include/llvm/MC/MCSectionELF.h b/llvm/include/llvm/MC/MCSectionELF.h
@@ -88,7 +88,6 @@ class MCSectionELF final : public MCSection {
                             raw_ostream &OS,
                             uint32_t Subsection) const override;
   bool useCodeAlign() const override;
-  StringRef getVirtualSectionKind() const override;
 
   bool isUnique() const { return UniqueID != NonUniqueID; }
   unsigned getUniqueID() const { return UniqueID; }

diff --git a/llvm/include/llvm/MC/MCStreamer.h b/llvm/include/llvm/MC/MCStreamer.h
@@ -427,8 +427,12 @@ class LLVM_ABI MCStreamer {
   }
 
   MCFragment *getCurrentFragment() const {
+    // Ensure consistency with the section stack.
     assert(!getCurrentSection().first ||
            CurFrag->getParent() == getCurrentSection().first);
+    // Ensure we eagerly allocate an empty fragment when adding fragment with a
+    // variable-size tail.
+    assert(!CurFrag || CurFrag->getKind() == MCFragment::FT_Data);
     return CurFrag;
   }
   /// Save the current and previous section on the section stack.

diff --git a/llvm/lib/MC/MCAssembler.cpp b/llvm/lib/MC/MCAssembler.cpp
@@ -567,15 +567,37 @@ void MCAssembler::writeSectionData(raw_ostream &OS,
     // not tracked for efficiency.
     auto Fn = [](char c) { return c != 0; };
     for (const MCFragment &F : *Sec) {
-      if (any_of(F.getContents(), Fn) || any_of(F.getVarContents(), Fn)) {
-        reportError(SMLoc(), Sec->getVirtualSectionKind() + " section '" +
-                                 Sec->getName() +
+      bool HasNonZero = false;
+      switch (F.getKind()) {
+      default:
+        reportFatalInternalError("BSS section '" + Sec->getName() +
+                                 "' contains invalid fragment");
+        break;
+      case MCFragment::FT_Data:
+      case MCFragment::FT_Relaxable:
+        HasNonZero =
+            any_of(F.getContents(), Fn) || any_of(F.getVarContents(), Fn);
+        break;
+      case MCFragment::FT_Align:
+        // Disallowed for API usage. AsmParser changes non-zero fill values to
+        // 0.
+        assert(F.getAlignFill() == 0 && "Invalid align in virtual section!");
+        break;
+      case MCFragment::FT_Fill:
+        HasNonZero = cast<MCFillFragment>(F).getValue() != 0;
+        break;
+      case MCFragment::FT_Org:
+        HasNonZero = cast<MCOrgFragment>(F).getValue() != 0;
+        break;
+      }
+      if (HasNonZero) {
+        reportError(SMLoc(), "BSS section '" + Sec->getName() +
                                  "' cannot have non-zero bytes");
         break;
       }
       if (F.getFixups().size() || F.getVarFixups().size()) {
-        reportError(SMLoc(), Sec->getVirtualSectionKind() + " section '" +
-                                 Sec->getName() + "' cannot have fixups");
+        reportError(SMLoc(),
+                    "BSS section '" + Sec->getName() + "' cannot have fixups");
         break;
       }
     }

diff --git a/llvm/lib/MC/MCObjectStreamer.cpp b/llvm/lib/MC/MCObjectStreamer.cpp
@@ -119,7 +119,7 @@ void MCObjectStreamer::emitCFISections(bool EH, bool Debug) {
 void MCObjectStreamer::emitValueImpl(const MCExpr *Value, unsigned Size,
                                      SMLoc Loc) {
   MCStreamer::emitValueImpl(Value, Size, Loc);
-  MCFragment *DF = getOrCreateDataFragment();
+  MCFragment *DF = getCurrentFragment();
 
   MCDwarfLineEntry::make(this, getCurrentSectionOnly());
 
@@ -168,7 +168,7 @@ void MCObjectStreamer::emitLabel(MCSymbol *Symbol, SMLoc Loc) {
   // If there is a current fragment, mark the symbol as pointing into it.
   // Otherwise queue the label and set its fragment pointer when we emit the
   // next fragment.
-  MCFragment *F = getOrCreateDataFragment();
+  MCFragment *F = getCurrentFragment();
   Symbol->setFragment(F);
   Symbol->setOffset(F->getContents().size());
 
@@ -202,7 +202,7 @@ void MCObjectStreamer::emitULEB128Value(const MCExpr *Value) {
     emitULEB128IntValue(IntValue);
     return;
   }
-  auto *F = getOrCreateDataFragment();
+  auto *F = getCurrentFragment();
   F->makeLEB(false, Value);
   newFragment();
 }
@@ -213,7 +213,7 @@ void MCObjectStreamer::emitSLEB128Value(const MCExpr *Value) {
     emitSLEB128IntValue(IntValue);
     return;
   }
-  auto *F = getOrCreateDataFragment();
+  auto *F = getCurrentFragment();
   F->makeLEB(true, Value);
   newFragment();
 }
@@ -312,7 +312,7 @@ void MCObjectStreamer::emitInstruction(const MCInst &Inst,
 
 void MCObjectStreamer::emitInstToData(const MCInst &Inst,
                                       const MCSubtargetInfo &STI) {
-  MCFragment *F = getOrCreateDataFragment();
+  MCFragment *F = getCurrentFragment();
 
   // Append the instruction to the data fragment.
   size_t FixupStartIndex = F->getFixups().size();
@@ -344,7 +344,7 @@ void MCObjectStreamer::emitInstToData(const MCInst &Inst,
 
 void MCObjectStreamer::emitInstToFragment(const MCInst &Inst,
                                           const MCSubtargetInfo &STI) {
-  auto *F = getOrCreateDataFragment();
+  auto *F = getCurrentFragment();
   SmallVector<char, 16> Data;
   SmallVector<MCFixup, 1> Fixups;
   getAssembler().getEmitter().encodeInstruction(Inst, Data, Fixups, STI);
@@ -417,7 +417,7 @@ void MCObjectStreamer::emitDwarfAdvanceLineAddr(int64_t LineDelta,
     return;
   }
 
-  auto *F = getOrCreateDataFragment();
+  auto *F = getCurrentFragment();
   F->Kind = MCFragment::FT_Dwarf;
   F->setDwarfAddrDelta(buildSymbolDiff(*this, Label, LastLabel, SMLoc()));
   F->setDwarfLineDelta(LineDelta);
@@ -449,7 +449,7 @@ void MCObjectStreamer::emitDwarfLineEndEntry(MCSection *Section,
 void MCObjectStreamer::emitDwarfAdvanceFrameAddr(const MCSymbol *LastLabel,
                                                  const MCSymbol *Label,
                                                  SMLoc Loc) {
-  auto *F = getOrCreateDataFragment();
+  auto *F = getCurrentFragment();
   F->Kind = MCFragment::FT_DwarfFrame;
   F->setDwarfAddrDelta(buildSymbolDiff(*this, Label, LastLabel, Loc));
   newFragment();
@@ -511,7 +511,7 @@ void MCObjectStreamer::emitCVFileChecksumOffsetDirective(unsigned FileNo) {
 
 void MCObjectStreamer::emitBytes(StringRef Data) {
   MCDwarfLineEntry::make(this, getCurrentSectionOnly());
-  MCFragment *DF = getOrCreateDataFragment();
+  MCFragment *DF = getCurrentFragment();
   DF->appendContents(ArrayRef(Data.data(), Data.size()));
 }
 

diff --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp
@@ -3406,9 +3406,8 @@ bool AsmParser::parseDirectiveAlign(bool IsPow2, uint8_t ValueSize) {
 
   if (HasFillExpr && FillExpr != 0 && Section->isVirtualSection()) {
     ReturnVal |=
-        Warning(FillExprLoc, "ignoring non-zero fill value in " +
-                                 Section->getVirtualSectionKind() +
-                                 " section '" + Section->getName() + "'");
+        Warning(FillExprLoc, "ignoring non-zero fill value in BSS section '" +
+                                 Section->getName() + "'");
     FillExpr = 0;
   }
 

diff --git a/llvm/lib/MC/MCSection.cpp b/llvm/lib/MC/MCSection.cpp
@@ -34,8 +34,6 @@ MCSymbol *MCSection::getEndSymbol(MCContext &Ctx) {
 
 bool MCSection::hasEnded() const { return End && End->isInSection(); }
 
-StringRef MCSection::getVirtualSectionKind() const { return "virtual"; }
-
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 LLVM_DUMP_METHOD void MCSection::dump(
     DenseMap<const MCFragment *, SmallVector<const MCSymbol *, 0>> *FragToSyms)

diff --git a/llvm/lib/MC/MCSectionCOFF.cpp b/llvm/lib/MC/MCSectionCOFF.cpp
@@ -115,7 +115,3 @@ void MCSectionCOFF::printSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
 }
 
 bool MCSectionCOFF::useCodeAlign() const { return isText(); }
-
-StringRef MCSectionCOFF::getVirtualSectionKind() const {
-  return "IMAGE_SCN_CNT_UNINITIALIZED_DATA";
-}
diff --git a/llvm/lib/MC/MCSectionELF.cpp b/llvm/lib/MC/MCSectionELF.cpp
@@ -215,5 +215,3 @@ void MCSectionELF::printSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
 bool MCSectionELF::useCodeAlign() const {
   return getFlags() & ELF::SHF_EXECINSTR;
 }
-
-StringRef MCSectionELF::getVirtualSectionKind() const { return "SHT_NOBITS"; }
diff --git a/llvm/lib/MC/MCWin64EH.cpp b/llvm/lib/MC/MCWin64EH.cpp
@@ -318,7 +318,7 @@ static void EmitUnwindInfo(MCStreamer &streamer, WinEH::FrameInfo *info) {
 
   // Emit the epilog instructions.
   if (EnableUnwindV2) {
-    MCFragment *DF = OS->getOrCreateDataFragment();
+    MCFragment *DF = OS->getCurrentFragment();
 
     bool IsLast = true;
     for (const auto &Epilog : llvm::reverse(info->EpilogMap)) {

diff --git a/llvm/lib/MC/MCWinCOFFStreamer.cpp b/llvm/lib/MC/MCWinCOFFStreamer.cpp
@@ -278,7 +278,7 @@ void MCWinCOFFStreamer::emitCOFFSymbolIndex(MCSymbol const *Symbol) {
 
 void MCWinCOFFStreamer::emitCOFFSectionIndex(const MCSymbol *Symbol) {
   visitUsedSymbol(*Symbol);
-  MCFragment *DF = getOrCreateDataFragment();
+  MCFragment *DF = getCurrentFragment();
   const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(Symbol, getContext());
   MCFixup Fixup = MCFixup::create(DF->getContents().size(), SRE, FK_SecRel_2);
   DF->addFixup(Fixup);
@@ -288,7 +288,7 @@ void MCWinCOFFStreamer::emitCOFFSectionIndex(const MCSymbol *Symbol) {
 void MCWinCOFFStreamer::emitCOFFSecRel32(const MCSymbol *Symbol,
                                          uint64_t Offset) {
   visitUsedSymbol(*Symbol);
-  MCFragment *DF = getOrCreateDataFragment();
+  MCFragment *DF = getCurrentFragment();
   // Create Symbol A for the relocation relative reference.
   const MCExpr *MCE = MCSymbolRefExpr::create(Symbol, getContext());
   // Add the constant offset, if given.
@@ -306,7 +306,7 @@ void MCWinCOFFStreamer::emitCOFFSecRel32(const MCSymbol *Symbol,
 void MCWinCOFFStreamer::emitCOFFImgRel32(const MCSymbol *Symbol,
                                          int64_t Offset) {
   visitUsedSymbol(*Symbol);
-  MCFragment *DF = getOrCreateDataFragment();
+  MCFragment *DF = getCurrentFragment();
   // Create Symbol A for the relocation relative reference.
   const MCExpr *MCE = MCSymbolRefExpr::create(
       Symbol, MCSymbolRefExpr::VK_COFF_IMGREL32, getContext());
@@ -324,7 +324,7 @@ void MCWinCOFFStreamer::emitCOFFImgRel32(const MCSymbol *Symbol,
 
 void MCWinCOFFStreamer::emitCOFFSecNumber(MCSymbol const *Symbol) {
   visitUsedSymbol(*Symbol);
-  MCFragment *DF = getOrCreateDataFragment();
+  MCFragment *DF = getCurrentFragment();
   // Create Symbol for section number.
   const MCExpr *MCE = MCCOFFSectionNumberTargetExpr::create(
       *Symbol, this->getWriter(), getContext());
@@ -338,7 +338,7 @@ void MCWinCOFFStreamer::emitCOFFSecNumber(MCSymbol const *Symbol) {
 
 void MCWinCOFFStreamer::emitCOFFSecOffset(MCSymbol const *Symbol) {
   visitUsedSymbol(*Symbol);
-  MCFragment *DF = getOrCreateDataFragment();
+  MCFragment *DF = getCurrentFragment();
   // Create Symbol for section offset.
   const MCExpr *MCE =
       MCCOFFSectionOffsetTargetExpr::create(*Symbol, getContext());

diff --git a/llvm/lib/MC/MCXCOFFStreamer.cpp b/llvm/lib/MC/MCXCOFFStreamer.cpp
@@ -89,7 +89,7 @@ void MCXCOFFStreamer::emitXCOFFSymbolLinkageWithVisibility(
 void MCXCOFFStreamer::emitXCOFFRefDirective(const MCSymbol *Symbol) {
   // Add a Fixup here to later record a relocation of type R_REF to prevent the
   // ref symbol from being garbage collected (by the binder).
-  MCFragment *DF = getOrCreateDataFragment();
+  MCFragment *DF = getCurrentFragment();
   const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(Symbol, getContext());
   std::optional<MCFixupKind> MaybeKind =
       getAssembler().getBackend().getFixupKind("R_REF");

diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
@@ -593,7 +593,7 @@ class ARMELFStreamer : public MCELFStreamer {
         getContext().reportError(Loc, "relocated expression must be 32-bit");
         return;
       }
-      getOrCreateDataFragment();
+      getCurrentFragment();
     }
 
     emitDataMappingSymbol();
@@ -1207,7 +1207,7 @@ inline void ARMELFStreamer::SwitchToExIdxSection(const MCSymbol &FnStart) {
 }
 
 void ARMELFStreamer::EmitFixup(const MCExpr *Expr, MCFixupKind Kind) {
-  MCFragment *Frag = getOrCreateDataFragment();
+  MCFragment *Frag = getCurrentFragment();
   Frag->addFixup(MCFixup::create(Frag->getContents().size(), Expr, Kind));
 }
 
@@ -1295,7 +1295,7 @@ void ARMELFStreamer::EmitPersonalityFixup(StringRef Name) {
       MCSymbolRefExpr::create(PersonalitySym, ARM::S_ARM_NONE, getContext());
 
   visitUsedExpr(*PersonalityRef);
-  MCFragment *DF = getOrCreateDataFragment();
+  MCFragment *DF = getCurrentFragment();
   DF->addFixup(
       MCFixup::create(DF->getContents().size(), PersonalityRef, FK_Data_4));
 }

diff --git a/llvm/lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp b/llvm/lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp
@@ -1033,42 +1033,42 @@ MCELFStreamer &MipsTargetELFStreamer::getStreamer() {
 }
 
 void MipsTargetELFStreamer::emitGPRel32Value(const MCExpr *Value) {
-  MCFragment *DF = getStreamer().getOrCreateDataFragment();
+  MCFragment *DF = getStreamer().getCurrentFragment();
   DF->addFixup(MCFixup::create(DF->getContents().size(), Value,
                                Mips::fixup_Mips_GPREL32));
   DF->appendContents(4, 0);
 }
 
 void MipsTargetELFStreamer::emitGPRel64Value(const MCExpr *Value) {
-  MCFragment *DF = getStreamer().getOrCreateDataFragment();
+  MCFragment *DF = getStreamer().getCurrentFragment();
   DF->addFixup(MCFixup::create(DF->getContents().size(), Value,
                                Mips::fixup_Mips_GPREL32));
   DF->appendContents(8, 0);
 }
 
 void MipsTargetELFStreamer::emitDTPRel32Value(const MCExpr *Value) {
-  MCFragment *DF = getStreamer().getOrCreateDataFragment();
+  MCFragment *DF = getStreamer().getCurrentFragment();
   DF->addFixup(MCFixup::create(DF->getContents().size(), Value,
                                Mips::fixup_Mips_DTPREL32));
   DF->appendContents(4, 0);
 }
 
 void MipsTargetELFStreamer::emitDTPRel64Value(const MCExpr *Value) {
-  MCFragment *DF = getStreamer().getOrCreateDataFragment();
+  MCFragment *DF = getStreamer().getCurrentFragment();
   DF->addFixup(MCFixup::create(DF->getContents().size(), Value,
                                Mips::fixup_Mips_DTPREL64));
   DF->appendContents(8, 0);
 }
 
 void MipsTargetELFStreamer::emitTPRel32Value(const MCExpr *Value) {
-  MCFragment *DF = getStreamer().getOrCreateDataFragment();
+  MCFragment *DF = getStreamer().getCurrentFragment();
   DF->addFixup(MCFixup::create(DF->getContents().size(), Value,
                                Mips::fixup_Mips_TPREL32));
   DF->appendContents(4, 0);
 }
 
 void MipsTargetELFStreamer::emitTPRel64Value(const MCExpr *Value) {
-  MCFragment *DF = getStreamer().getOrCreateDataFragment();
+  MCFragment *DF = getStreamer().getCurrentFragment();
   DF->addFixup(MCFixup::create(DF->getContents().size(), Value,
                                Mips::fixup_Mips_TPREL64));
   DF->appendContents(8, 0);

diff --git a/llvm/test/MC/COFF/bss-text.s b/llvm/test/MC/COFF/bss-text.s
@@ -4,11 +4,11 @@
 # RUN: llvm-mc -triple=x86_64-pc-win32 %s
 
 .bss
-# CHECK: <unknown>:0: error: IMAGE_SCN_CNT_UNINITIALIZED_DATA section '.bss' cannot have non-zero bytes
+# CHECK: <unknown>:0: error: BSS section '.bss' cannot have non-zero bytes
   addb %bl,(%rax)
 
 .section uninitialized,"b"
-# CHECK: <unknown>:0: error: IMAGE_SCN_CNT_UNINITIALIZED_DATA section 'uninitialized' cannot have non-zero bytes
+# CHECK: <unknown>:0: error: BSS section 'uninitialized' cannot have non-zero bytes
   jmp foo
 
 .section bss0,"b"