DebugInfo: Support for compressed debug info sections

1) When creating a .debug_* section and instead create a .zdebug_
   section.
2) When creating a fragment in a .zdebug_* section, make it a compressed
   fragment.
3) When computing the size of a compressed section, compress the data
   and use the size of the compressed data.
4) Emit the compressed bytes.

Also, check that only if a section has a compressed fragment, then that
is the only fragment in the section.

Assert-fail if the fragment's data is modified after it is compressed.

Initial review on llvm-commits by Eric Christopher and Rafael Espindola.

llvm-svn: 204958

1 files changed, 12 insertions, 7 deletions

diff --git a/llvm/lib/MC/MCContext.cpp b/llvm/lib/MC/MCContext.cpp
index ede3b3cd235..b228d18ba7f 100644
--- a/llvm/lib/MC/MCContext.cpp
+++ b/llvm/lib/MC/MCContext.cpp
@@ -37,13 +37,13 @@ typedef std::map<SectionGroupPair, const MCSectionCOFF *> COFFUniqueMapTy;
 
 MCContext::MCContext(const MCAsmInfo *mai, const MCRegisterInfo *mri,
                      const MCObjectFileInfo *mofi, const SourceMgr *mgr,
-                     bool DoAutoReset) :
-  SrcMgr(mgr), MAI(mai), MRI(mri), MOFI(mofi),
-  Allocator(), Symbols(Allocator), UsedNames(Allocator),
-  NextUniqueID(0),
-  CurrentDwarfLoc(0,0,0,DWARF2_FLAG_IS_STMT,0,0),
-  DwarfLocSeen(false), GenDwarfForAssembly(false), GenDwarfFileNumber(0),
-  AllowTemporaryLabels(true), DwarfCompileUnitID(0), AutoReset(DoAutoReset) {
+                     bool DoAutoReset)
+    : SrcMgr(mgr), MAI(mai), MRI(mri), MOFI(mofi), Allocator(),
+      Symbols(Allocator), UsedNames(Allocator), NextUniqueID(0),
+      CurrentDwarfLoc(0, 0, 0, DWARF2_FLAG_IS_STMT, 0, 0), DwarfLocSeen(false),
+      GenDwarfForAssembly(false), GenDwarfFileNumber(0),
+      AllowTemporaryLabels(true), DwarfCompileUnitID(0),
+      AutoReset(DoAutoReset) {
 
   error_code EC = llvm::sys::fs::current_path(CompilationDir);
   if (EC)
@@ -251,6 +251,11 @@ getELFSection(StringRef Section, unsigned Type, unsigned Flags,
     ELFUniquingMap = new ELFUniqueMapTy();
   ELFUniqueMapTy &Map = *(ELFUniqueMapTy*)ELFUniquingMap;
 
+  SmallString<32> ZDebugName;
+  if (MAI->compressDebugSections() && Section.startswith(".debug_") &&
+      Section != ".debug_frame")
+    Section = (".z" + Section.drop_front(1)).toStringRef(ZDebugName);
+
   // Do the lookup, if we have a hit, return it.
   std::pair<ELFUniqueMapTy::iterator, bool> Entry = Map.insert(
       std::make_pair(SectionGroupPair(Section, Group), (MCSectionELF *)0));