[PATCH] D21743: Convenience function for MCStreamer to get named sections when lowering.

[Dean Michael Berris via llvm-commits]

dberris created this revision.
dberris added reviewers: echristo, grosbach.
dberris added a subscriber: llvm-commits.
Herald added a subscriber: mehdi_amini.

This change allows us to create uniquely identified "COMDAT" or "ELF
Group" sections while lowering. In particular, for ELF sections this is
useful for creating function-specific groups that get merged into the
same named section.

http://reviews.llvm.org/D21743

Files:
  include/llvm/MC/MCELFStreamer.h
  include/llvm/MC/MCStreamer.h
  lib/MC/MCELFStreamer.cpp
  lib/MC/MCStreamer.cpp

Index: lib/MC/MCStreamer.cpp
===================================================================
--- lib/MC/MCStreamer.cpp
+++ lib/MC/MCStreamer.cpp
@@ -806,3 +806,8 @@
   EmitLabel(Sym);
   return Sym;
 }
+
+MCSection *MCStreamer::getNamedGroupSection(StringRef, StringRef, unsigned) {
+  llvm_unreachable("Unimplemented.");
+  return nullptr;
+}
Index: lib/MC/MCELFStreamer.cpp
===================================================================
--- lib/MC/MCELFStreamer.cpp
+++ lib/MC/MCELFStreamer.cpp
@@ -672,3 +672,11 @@
                                    uint64_t Size, unsigned ByteAlignment) {
   llvm_unreachable("ELF doesn't support this directive");
 }
+
+MCSection *MCELFStreamer::getNamedGroupSection(StringRef Section,
+                                               StringRef Identifier,
+                                               unsigned EntSize) {
+  return getContext().getELFSection(Section, ELF::SHT_PROGBITS,
+                                    ELF::SHF_ALLOC | ELF::SHF_GROUP, EntSize,
+                                    Identifier);
+}
Index: include/llvm/MC/MCStreamer.h
===================================================================
--- include/llvm/MC/MCStreamer.h
+++ include/llvm/MC/MCStreamer.h
@@ -760,6 +760,12 @@
   /// Get the .xdata section used for the given section.
   MCSection *getAssociatedXDataSection(const MCSection *TextSec);
 
+  /// Get a group section with provided group identifier. This is in ELF, for
+  /// instance, named by concatenating \p Section with '.' then \p Identifier.
+  virtual MCSection *getNamedGroupSection(StringRef Section,
+                                          StringRef Identifier,
+                                          unsigned EntSize);
+
   virtual void EmitSyntaxDirective();
 
   /// \brief Emit a .reloc directive.
Index: include/llvm/MC/MCELFStreamer.h
===================================================================
--- include/llvm/MC/MCELFStreamer.h
+++ include/llvm/MC/MCELFStreamer.h
@@ -81,6 +81,9 @@
   void EmitBundleLock(bool AlignToEnd) override;
   void EmitBundleUnlock() override;
 
+  MCSection *getNamedGroupSection(StringRef Section, StringRef Identifer,
+                                  unsigned EntSize) override;
+
 private:
   bool isBundleLocked() const;
   void EmitInstToFragment(const MCInst &Inst, const MCSubtargetInfo &) override;


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