Refactor how passes get a symbol at the end of a section.

There is now a canonical symbol at the end of a section that different
passes can request.

This also allows us to assert that we don't switch back to a section whose
end symbol has already been printed.

llvm-svn: 233026

4 files changed, 30 insertions, 24 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index bc9a67640fb..e9ebd97dab0 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1664,15 +1664,8 @@ void DwarfDebug::emitDebugARanges() {
     const MCSection *Section = I.first;
     MCSymbol *Sym = nullptr;
 
-    if (Section) {
-      // We can't call MCSection::getLabelEndName, as it's only safe to do so
-      // if we know the section name up-front. For user-created sections, the
-      // resulting label may not be valid to use as a label. (section names can
-      // use a greater set of characters on some systems)
-      Sym = Asm->createTempSymbol("debug_end");
-      Asm->OutStreamer.SwitchSection(Section);
-      Asm->OutStreamer.EmitLabel(Sym);
-    }
+    if (Section)
+      Sym = Asm->OutStreamer.endSection(Section);
 
     // Insert a final terminator.
     SectionMap[Section].push_back(SymbolCU(nullptr, Sym));
diff --git a/llvm/lib/MC/MCDwarf.cpp b/llvm/lib/MC/MCDwarf.cpp
index 91b277cee5c..24cdaeff494 100644
--- a/llvm/lib/MC/MCDwarf.cpp
+++ b/llvm/lib/MC/MCDwarf.cpp
@@ -179,23 +179,14 @@ EmitDwarfLineTable(MCObjectStreamer *MCOS, const MCSection *Section,
   }
 
   // Emit a DW_LNE_end_sequence for the end of the section.
-  // Using the pointer Section create a temporary label at the end of the
-  // section and use that and the LastLabel to compute the address delta
-  // and use INT64_MAX as the line delta which is the signal that this is
-  // actually a DW_LNE_end_sequence.
-
-  // Switch to the section to be able to create a symbol at its end.
-  // TODO: keep track of the last subsection so that this symbol appears in the
-  // correct place.
-  MCOS->SwitchSection(Section);
+  // Use the section end label to compute the address delta and use INT64_MAX
+  // as the line delta which is the signal that this is actually a
+  // DW_LNE_end_sequence.
+  MCSymbol *SectionEnd = MCOS->endSection(Section);
 
+  // Switch back the dwarf line section, in case endSection had to switch the
+  // section.
   MCContext &Ctx = MCOS->getContext();
-  // Create a symbol at the end of the section.
-  MCSymbol *SectionEnd = Ctx.CreateTempSymbol();
-  // Set the value of the symbol, as we are at the end of the section.
-  MCOS->EmitLabel(SectionEnd);
-
-  // Switch back the dwarf line section.
   MCOS->SwitchSection(Ctx.getObjectFileInfo()->getDwarfLineSection());
 
   const MCAsmInfo *AsmInfo = Ctx.getAsmInfo();
diff --git a/llvm/lib/MC/MCSection.cpp b/llvm/lib/MC/MCSection.cpp
index ccf4a7dddf7..7889f837b11 100644
--- a/llvm/lib/MC/MCSection.cpp
+++ b/llvm/lib/MC/MCSection.cpp
@@ -10,6 +10,7 @@
 #include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCSymbol.h"
 #include "llvm/Support/raw_ostream.h"
 using namespace llvm;
 
@@ -17,6 +18,14 @@ using namespace llvm;
 // MCSection
 //===----------------------------------------------------------------------===//
 
+MCSymbol *MCSection::getEndSymbol(MCContext &Ctx) const {
+  if (!End)
+    End = Ctx.createTempSymbol("sec_end", true);
+  return End;
+}
+
+bool MCSection::hasEnded() const { return End && End->isInSection(); }
+
 MCSection::~MCSection() {
 }
 
diff --git a/llvm/lib/MC/MCStreamer.cpp b/llvm/lib/MC/MCStreamer.cpp
index 63b0bf2c80f..27d0355bb11 100644
--- a/llvm/lib/MC/MCStreamer.cpp
+++ b/llvm/lib/MC/MCStreamer.cpp
@@ -670,9 +670,22 @@ void MCStreamer::SwitchSection(const MCSection *Section,
   SectionStack.back().second = curSection;
   if (MCSectionSubPair(Section, Subsection) != curSection) {
     SectionStack.back().first = MCSectionSubPair(Section, Subsection);
+    assert(!Section->hasEnded() && "Section already ended");
     ChangeSection(Section, Subsection);
     MCSymbol *Sym = Section->getBeginSymbol();
     if (Sym && !Sym->isInSection())
       EmitLabel(Sym);
   }
 }
+
+MCSymbol *MCStreamer::endSection(const MCSection *Section) {
+  // TODO: keep track of the last subsection so that this symbol appears in the
+  // correct place.
+  MCSymbol *Sym = Section->getEndSymbol(Context);
+  if (Sym->isInSection())
+    return Sym;
+
+  SwitchSection(Section);
+  EmitLabel(Sym);
+  return Sym;
+}